U.S. patent application number 14/921394 was filed with the patent office on 2017-04-27 for contour follower apparatus and related systems and methods.
The applicant listed for this patent is Flow International Corporation. Invention is credited to Kenneth E. Claeys, Kirby J. Eide, Ethan E. Romanoff.
Application Number | 20170113324 14/921394 |
Document ID | / |
Family ID | 57233886 |
Filed Date | 2017-04-27 |
United States Patent
Application |
20170113324 |
Kind Code |
A1 |
Romanoff; Ethan E. ; et
al. |
April 27, 2017 |
CONTOUR FOLLOWER APPARATUS AND RELATED SYSTEMS AND METHODS
Abstract
Systems and related methods are provided for maintaining a
spatial relationship between a tool of the multi-axis machine
(e.g., fluid jet nozzle of a fluid jet cutting machine) and a
workpiece to be processed by the tool. An example system includes a
contour follower apparatus having a sensor and a gimbal assembly
operable with the sensor to sense a deviation between a machine
focal point and a gimbal assembly focal point defined by the gimbal
assembly as the gimbal assembly rides upon the surface of the
workpiece during operation. The system may further include a gimbal
mount assembly configured to sense a collision event of the gimbal
assembly with another object.
Inventors: |
Romanoff; Ethan E.; (Bonney
Lake, WA) ; Claeys; Kenneth E.; (Kent, WA) ;
Eide; Kirby J.; (Des Moines, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Flow International Corporation |
Kent |
WA |
US |
|
|
Family ID: |
57233886 |
Appl. No.: |
14/921394 |
Filed: |
October 23, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23Q 17/2241 20130101;
B24C 1/045 20130101; B23Q 17/2208 20130101; B26F 3/004 20130101;
B23Q 17/2233 20130101 |
International
Class: |
B24C 1/04 20060101
B24C001/04 |
Claims
1. A gimbal assembly for a multi-axis machine to assist in
maintaining a spatial relationship between a tool of the multi-axis
machine and a workpiece to be processed by the tool, the multi-axis
machine including two axes of rotation that intersect to define a
machine focal point, the gimbal assembly comprising: a swivel arm
operable to rotate about a first axis of rotation; and a contact
member rotatably coupled to the swivel arm to rotate about a second
axis of rotation which intersects with the first axis of rotation
to define a gimbal assembly focal point, the contact member
including one or more surface features arranged to ride upon a
surface of the workpiece during operation and to define a reference
plane that contains the gimbal assembly focal point, and wherein
the gimbal assembly enables sensing of a deviation between the
machine focal point and the gimbal assembly focal point as the
contact member rides upon the surface of the workpiece during
operation.
2. The gimbal assembly of claim 1 wherein the gimbal assembly
includes a gimbal base and the gimbal assembly is configured such
that the deviation of the machine focal point from the gimbal
assembly focal point results in a corresponding displacement of the
gimbal base.
3. The gimbal assembly of claim 1 wherein the gimbal assembly is
configured to adjust to changes in topography of the workpiece via
rotational movement of the swivel arm and contact member about the
first and second axes of rotation, respectively, while the gimbal
assembly simultaneously enables sensing of any deviation between
the machine focal point and the gimbal assembly focal point.
4. The gimbal assembly of claim 1, further comprising: at least one
swivel lock to selectively prevent rotation of the swivel arm about
the first axis of rotation or rotation of the contact member about
the second axis of rotation.
5. The gimbal assembly of claim 1, further comprising: at least one
rotational stop to limit rotation of the swivel arm about the first
axis of rotation or rotation of the contact member about the second
axis of rotation.
6. The gimbal assembly of claim 1, further comprising: encoders for
measuring a surface topography of the workpiece based on a
respective sensed rotational position of the swivel arm and the
contact member.
7. The gimbal assembly of claim 1, further comprising: encoders for
measuring a surface topography of the workpiece based on a
respective sensed rotational position of the swivel arm and the
contact member and for keeping the tool at a defined orientation
relative to the surface topography.
8. A contour follower apparatus for a multi-axis machine to assist
in maintaining a spatial relationship between a tool of the
multi-axis machine and a workpiece to be processed by the tool, the
multi-axis machine including two axes of rotation that intersect to
define a machine focal point, the contour follower apparatus
comprising: a sensor; and a gimbal assembly operable with the
sensor to sense a deviation between the machine focal point and a
gimbal assembly focal point defined by the gimbal assembly as the
gimbal assembly rides upon the surface of the workpiece during
operation.
9. The contour follower apparatus of claim 8, further comprising: a
gimbal mount assembly for coupling the gimbal assembly to the
multi-axis machine and for sensing a collision event of the gimbal
assembly with another object.
10. The contour follower apparatus of claim 9 wherein the gimbal
assembly includes a coupling arrangement which removably couples
the gimbal assembly to the gimbal mount assembly, the coupling
arrangement being configured to allow detachment of the gimbal
assembly from the gimbal mount assembly without manipulating any
fasteners.
11. The contour follower apparatus of claim 10 wherein the coupling
arrangement includes at least one alignment device that establishes
and maintains a predetermined spatial relationship between a base
of the gimbal assembly and a base of the gimbal mount assembly and
at least one magnetic device that urges the base of the gimbal
assembly and the base of the gimbal mount assembly together.
12. The contour follower apparatus of claim 9 wherein the gimbal
mount assembly includes a collision sensor arrangement comprising a
collision sensor and a sensor member that is displaced during the
collision event to cause the collision sensor to generate a
collision event signal.
13. The contour follower apparatus of claim 12 wherein the
collision sensor arrangement includes a ramp, and wherein the
sensor member is forced to move vertically by the ramp during the
collision event to cause the collision sensor to generate the
collision event signal.
14. The contour follower apparatus of claim 12 wherein the
collision sensor arrangement is located remote from the gimbal
assembly so as to not compromise movement of the gimbal assembly as
the gimbal assembly rides on the workpiece during operation.
15. The contour follower apparatus of claim 9 wherein the gimbal
mount assembly is constrained relative to the tool to move
linearly.
16. The contour follower apparatus of claim 9 wherein the gimbal
mount assembly is configured to provide a rigid connection between
the gimbal assembly and the multi-axis machine which breaks free
during a collision event.
17. The contour follower apparatus of claim 8, further comprising:
at least one actuator for deploying and retracting the gimbal
assembly into and out of an active configuration.
18. A fluid jet cutting system, the system comprising: a fluid jet
cutting head manipulable in space via a multi-axis machine that
includes two axes of rotation that intersect to define a machine
focal point, the fluid jet cutting head including a nozzle from
which a high pressure fluid jet is discharged during operation to
process a workpiece; and a contour follower apparatus comprising a
sensor and a gimbal assembly that includes a swivel arm operable to
rotate about a first axis of rotation and a contact member
rotatably coupled to the swivel arm to rotate about a second axis
of rotation which intersects with the first axis of rotation to
define a gimbal assembly focal point, the contact member including
one or more surface features arranged to ride upon a surface of the
workpiece during operation and to define a reference plane that
contains the gimbal assembly focal point, and wherein the sensor
operates in conjunction with the gimbal assembly of the contour
follower apparatus to sense a deviation between the machine focal
point and the gimbal assembly focal point as the contact member
rides upon the surface of the workpiece during operation.
19. The fluid jet cutting system of claim 18, further comprising: a
gimbal mount assembly that couples the gimbal assembly to the
multi-axis machine and is configured to sense a collision event of
the gimbal assembly with another object.
20. The fluid jet cutting system of claim 18 wherein the gimbal
assembly is configured to adjust to changes in topography of the
workpiece via rotational movement of the swivel arm and contact
member about the first and second axes of rotation, respectively,
while the gimbal assembly simultaneously enables sensing of any
deviation between the machine focal point and the gimbal assembly
focal point.
21. A method of controlling a standoff distance of a nozzle of a
fluid jet cutting head manipulable in space via a multi-axis
machine having two axes of rotation that intersect to define a
machine focal point, the method comprising: manipulating the fluid
jet cutting head relative to a workpiece to be processed such that
a gimbal assembly associated with the fluid jet cutting head rides
upon a surface of the workpiece, the gimbal assembly including two
axes of rotation that intersect to define a gimbal assembly focal
point; and sensing a deviation between the machine focal point and
the gimbal assembly focal point for adjusting the standoff distance
of the nozzle.
22. The method of claim 21, further comprising: adjusting the
standoff distance of the nozzle toward a state in which the machine
focal point and the gimbal assembly focal point are coincident.
23. The method claim 21 wherein sensing the deviation between the
machine focal point and the gimbal assembly focal point for
adjusting the standoff distance of the nozzle includes sensing a
change in distance between the nozzle and the surface of the
workpiece as the contact member rides upon the surface of the
workpiece during operation.
24. The method of claim 23 wherein the machine focal point and the
gimbal assembly focal point are not coincident when sensing the
change in distance between the nozzle and the surface of the
workpiece.
25. The method of claim 21, further comprising: adjusting the
standoff distance of the nozzle toward a state in which a distance
between the machine focal point and the gimbal assembly focal point
is a predetermined value.
26. The method of claim 21 wherein the gimbal assembly comprises a
gimbal base, a swivel arm rotatably coupled to the gimbal base to
rotate about a first axis of rotation, and a contact member
rotatably coupled to the swivel arm to rotate about a second axis
of rotation which intersects with the first axis of rotation to
define the gimbal assembly focal point, the contact member
including one or more surface features arranged to ride upon the
surface of the workpiece during operation and to define a reference
plane that contains the gimbal assembly focal point, and wherein
sensing the deviation between the machine focal point and the
gimbal assembly focal point includes sensing a displacement of the
gimbal base while the gimbal assembly rides on the surface of the
workpiece.
27. The method of claim 21 wherein sensing the deviation between
the machine focal point and the gimbal assembly focal point
includes allowing the gimbal assembly to adjust to changes in
topography of the workpiece via rotational movement of a swivel arm
and contact member about the first and second axes of rotation,
respectively.
28. The method of claim 21, further comprising: sensing a collision
of the gimbal assembly with another object; and adjusting operation
of the multi-axis machine in response to the collision.
29. The method of claim 21 wherein sensing a collision includes
converting an impact applied to the gimbal assembly during the
collision to vertical movement of a sensor member to generate a
collision event signal.
30. A collision detection system for a multi-axis machine to assist
in sensing an impending collision between a tool of the multi-axis
machine and another object, the collision detection system
including: a contour follower apparatus configured to ride upon a
surface of the workpiece during operation; and a collision sensor
arrangement operatively coupled to the contour follower apparatus
to sense the impending collision, the collision sensor arrangement
including a collision sensor and a sensor member that is
constrained such that torque applied to the sensor member during a
collision event is converted to displacement of the sensor member
into engagement with the collision sensor to cause the collision
sensor to generate a collision event signal.
31. The collision detection system of claim 30 wherein the contour
follower apparatus comprises a gimbal assembly, the gimbal assembly
including a swivel arm operable to rotate about a first axis of
rotation and a contact member rotatably coupled to the swivel arm
to rotate about a second axis of rotation, and the contact member
including one or more surface features arranged to ride upon the
surface of the workpiece during operation.
32. The collision detection system of claim 31 wherein the
collision sensor arrangement is located remote from the gimbal
assembly so as to not compromise movement of the gimbal assembly as
the gimbal assembly rides on the workpiece during operation.
33. The collision detection system of claim 31 wherein the
collision sensor arrangement is part of a mount assembly that is
constrained relative to the tool to move linearly.
34. The collision detection system of claim 33 wherein the mount
assembly is configured to provide a rigid connection between the
gimbal assembly and the multi-axis machine which breaks free during
a collision event.
35. The collision detection system of claim 30 wherein the
collision sensor arrangement includes a seat having a ramp portion,
and wherein the sensor member is forced to move vertically by the
ramp portion of the seat during the collision event to cause the
collision sensor to generate the collision event signal.
36. The collision detection system of claim 35 wherein the sensor
member is biased towards the seat.
37. A fluid jet cutting system, the system comprising: a multi-axis
machine; a fluid jet cutting head manipulable in space via the
multi-axis machine, the fluid jet cutting head including a nozzle
from which a high pressure fluid jet is discharged during operation
to process a workpiece; and a gimbal assembly coupled to the
multi-axis machine and being configured to ride upon a surface of
the workpiece in a vicinity of the nozzle of the fluid jet cutting
head during operation.
38. The system of claim 37 wherein the gimbal assembly includes a
swivel arm operable to rotate about a first axis of rotation and a
contact member rotatably coupled to the swivel arm to rotate about
a second axis of rotation, and the contact member includes one or
more surface features arranged to ride upon the surface of the
workpiece during operation.
39. The system of claim 37, further comprising: a collision sensor
arrangement operatively coupled to the gimbal assembly to sense an
impending collision between the nozzle of the multi-axis machine
and another object.
40. The system of claim 39 wherein the collision sensor arrangement
is located remote from the gimbal assembly so as to not compromise
movement of the gimbal assembly as the gimbal assembly rides on the
workpiece during operation.
41. The system of claim 39 wherein the collision sensor arrangement
is part of a gimbal mount assembly that is constrained relative to
the nozzle of the fluid jet cutting head to move linearly.
42. The system of claim 41 wherein the gimbal mount assembly is
configured to provide a rigid connection between the gimbal
assembly and the multi-axis machine which breaks free during a
collision event.
43. The system of claim 39 wherein the collision sensor arrangement
includes a seat having a ramp portion, and wherein the sensor
member is forced to move vertically by the ramp portion of the seat
during the collision event to cause the collision sensor to
generate the collision event signal.
44. The system of claim 43 wherein the sensor member is biased
towards the seat.
45. A gimbal assembly for a multi-axis machine to assist in
maintaining a spatial relationship between a tool of the multi-axis
machine and a workpiece to be processed by the tool, the gimbal
assembly comprising: a swivel arm operable to rotate about a first
axis of rotation; and a contact member rotatably coupled to the
swivel arm to rotate about a second axis of rotation, the contact
member including one or more surface features arranged to ride upon
a surface of the workpiece during operation, and wherein the gimbal
assembly enables sensing a change in distance between the tool and
the surface of the workpiece as the contact member rides upon the
surface of the workpiece during operation.
Description
BACKGROUND
[0001] Technical Field
[0002] This disclosure relates to systems and methods for
maintaining a spatial relationship between a tool of a multi-axis
machine (e.g., a fluid jet nozzle of a fluid jet cutting machine)
and a workpiece to be processed by the tool. The disclosure also
relates to systems and methods for sensing collisions with an
obstruction in the controlled path of the tool and adjusting
operation of the machine accordingly.
[0003] Description of the Related Art
[0004] High-pressure fluid jets, including high-pressure abrasive
waterjets, are used to cut a wide variety of materials in many
different industries. Systems for generating high-pressure abrasive
waterjets are currently available, such as, for example, the Mach
4.TM. five-axis abrasive waterjet system manufactured by Flow
International Corporation, the assignee of the present invention,
as well as other systems that include a cutting head assembly
mounted to an articulated robotic arm or other motion system. Other
examples of abrasive fluid jet cutting systems are shown and
described in Flow's U.S. Pat. No. 5,643,058, which is incorporated
herein by reference. The terms "high-pressure fluid jet" and "jet"
should be understood to incorporate all types of high-pressure
fluid jets, including but not limited to high-pressure waterjets
and high-pressure abrasive waterjets. In such systems,
high-pressure fluid, typically water, flows through an orifice of
an orifice unit in a cutting head to form a high-pressure jet, into
which abrasive particles may be combined as the jet flows through a
mixing chamber and a mixing tube to form a high-pressure abrasive
waterjet. The high-pressure abrasive waterjet is typically
discharged from the mixing tube and directed toward a workpiece to
cut the workpiece along a designated path.
[0005] Various systems are currently available to move a
high-pressure fluid jet along a designated path. Such systems may
commonly be referred to as, for example, three-axis and five-axis
machines. Conventional three-axis machines mount the cutting head
assembly in such a way that it can move along an x-y plane and
perpendicularly thereto along a z-axis, namely toward and away from
the workpiece. In this manner, the high-pressure fluid jet
generated by the cutting head assembly is moved along the
designated path in an x-y plane, and is raised and lowered relative
to the workpiece, as may be desired. Conventional five-axis
machines work in a similar manner but provide for movement about
two additional non-parallel rotary axes. Other systems may include
a cutting head assembly mounted to an articulated robotic arm, such
as, for example, a six-axis robotic arm which articulates about six
separate rotary axes.
[0006] Computer-aided manufacturing (CAM) processes may be used to
drive or control such conventional machines along a designated
path, such as by enabling two-dimensional or three-dimensional
models of workpieces generated using computer-aided design (i.e.,
CAD models) to be used to generate code to drive the machines. For
example, a CAD model may be used to generate instructions to drive
the appropriate controls and motors of the machine to manipulate
the machine about its translational and/or rotary axes to cut or
process a workpiece as reflected in the model.
[0007] During the fluid jet cutting process, dimensional accuracy
and cut quality may be dependent on, among other things, precisely
maintaining a desired distance between the end of the nozzle or
mixing tube and the surface of the workpiece being cut, often
referred to as the standoff distance. Maintaining a precise
standoff distance becomes particularly important as fluid jet
cutting technology advances from flat-stock 2-D cutting, to
applications involving curved material, beveled cuts and other
complex cutting profiles enabled by five-axis and other multi-axis
control.
[0008] Historically, for example, commanded five-axis motion
control of 2-D flat stock cutting is based on compound angle
calculations evaluated based on the inferred ("nominal") distance
between the end of the nozzle or mixing tube and the surface of the
workpiece to be cut. In reality, the actual standoff distance will
deviate from the nominal distance, for example, warping due to
stress relieving of material during the cut, natural material bow,
or the "as provided" state from a manufacturer will introduce error
into any cut edge off of the vertical axis. This error is
particularly apparent and undesirable as the cut edge shifts
further from vertical, for example, in an intentional bevel cut.
The example contour follower apparatus and related systems and
methods described herein help to ensure that the distance between
the focal point of the machine is known relative to the surface of
the workpiece being cut. This allows the controller to hold the
machine focal point on the surface of the workpiece despite any
deviations in the terrain of the workpiece and provides enhanced
functionality over prior standoff distance control systems and
methodologies, such as those shown and described in Flow's U.S.
Pat. No. 7,331,842. For example, the example contour follower
apparatus and related systems and methods provide, among other
things, enhanced accuracy with which the standoff distance is
maintained, including when cutting at particularly steep angles,
such as when making an intentional bevel cut.
BRIEF SUMMARY
[0009] Embodiments described herein provide enhanced systems and
methods for maintaining a spatial relationship between a tool of a
multi-axis machine (e.g., a fluid jet nozzle of a fluid jet cutting
machine) and a workpiece to be processed by the tool to improve
performance. For example, one embodiment is directed to a contour
follower apparatus that is to be mounted on the end effector of a
fluid jet cutting machine. During the fluid jet cutting process,
the contour follower apparatus monitors the distance between the
focal point of the end effector and the surface of the workpiece
being cut. Changes in this distance are transmitted to the
machine's motion controller as a variable signal, in turn allowing
the controller to adjust, in real time, the mechanical actuators
which establish the standoff distance being measured. This feedback
control maintains the focal point of the end effector directly on
the surface of the workpiece being cut, thus optimizing the
dimensional accuracy of the cut workpiece. Embodiments described
herein may also provide enhanced systems and methods for sensing
collisions with an obstruction in the controlled path of the tool
and adjusting operation accordingly.
[0010] One embodiment of a gimbal assembly for a multi-axis machine
to assist in maintaining a spatial relationship between a tool of
the multi-axis machine and a workpiece to be processed by the tool
may be summarized as including: a swivel arm operable to rotate
about a first axis of rotation; and a contact member rotatably
coupled to the swivel arm to rotate about a second axis of rotation
which intersects with the first axis of rotation to define a gimbal
assembly focal point. The contact member may further include one or
more surface features arranged to ride upon a surface of the
workpiece during operation and to define a reference plane that
contains the gimbal assembly focal point. Advantageously, the
gimbal assembly enables sensing of a deviation between a machine
focal point (defined by the intersection of two axes of rotation of
the machine) and the gimbal assembly focal point as the contact
member rides upon the surface of the workpiece during
operation.
[0011] The gimbal assembly may further include a gimbal base and
the gimbal assembly may be configured such that the deviation of
the machine focal point from the gimbal assembly focal point
results in a corresponding displacement of the gimbal base. The
gimbal assembly may be configured to adjust to changes in
topography of the workpiece via rotational movement of the swivel
arm and the contact member about the first and second axes of
rotation, respectively, while the gimbal assembly simultaneously
enables sensing of any deviation between the machine focal point
and the gimbal assembly focal point.
[0012] The gimbal assembly may further include at least one swivel
lock to selectively prevent rotation of the swivel arm about the
first axis of rotation or rotation of the contact member about the
second axis of rotation. The gimbal assembly may further include at
least one rotational stop to limit rotation of the swivel arm about
the first axis of rotation or rotation of the contact member about
the second axis of rotation. The gimbal assembly may further
include encoders for measuring a surface topography of the
workpiece based on a respective sensed rotational position of the
swivel arm and the contact member. Signals from the encoders may
also be used to maintain the tool at a defined orientation (e.g.,
perpendicular orientation) relative to the surface topography.
[0013] One embodiment of contour follower apparatus for a
multi-axis machine to assist in maintaining a spatial relationship
between a tool of the multi-axis machine and a workpiece to be
processed by the tool may be summarized as including: a sensor; and
a gimbal assembly operable with the sensor to sense a deviation
between a machine focal point (defined by the intersection of two
axes of rotation of the machine) and a gimbal assembly focal point
defined by the gimbal assembly as the gimbal assembly rides upon
the surface of the workpiece during operation.
[0014] The contour follower may further include a gimbal mount
assembly for coupling the gimbal assembly to the multi-axis machine
and for sensing a collision event of the gimbal assembly with
another object. The gimbal assembly may include a coupling
arrangement which removably couples the gimbal assembly to the
gimbal mount assembly, the coupling arrangement being configured to
allow detachment of the gimbal assembly from the gimbal mount
assembly without manipulating any fasteners. The coupling
arrangement may include at least one alignment device that
establishes and maintains a predetermined spatial relationship
between a base of the gimbal assembly and a base of the gimbal
mount assembly and at least one magnetic device that urges the base
of the gimbal assembly and the base of the gimbal mount assembly
together. The gimbal mount assembly may include a collision sensor
arrangement comprising a collision sensor and a sensor member that
is displaced during the collision event to cause the collision
sensor to generate a collision event signal. The collision sensor
arrangement may include a ramp, and the sensor member may be forced
to move vertically by the ramp during the collision event to cause
the collision sensor to generate the collision event signal. The
collision sensor arrangement may be located remote from the gimbal
assembly so as to not compromise movement of the gimbal assembly as
the gimbal assembly rides on the workpiece during operation. The
gimbal mount assembly may be constrained relative to the tool to
move linearly. The gimbal mount assembly may be configured to
provide a rigid connection between the gimbal assembly and the
multi-axis machine which breaks free during a collision event. The
contour follower apparatus may further include at least one
actuator for deploying and retracting the gimbal assembly into and
out of an active configuration.
[0015] One embodiment of a fluid jet cutting system may be
summarized as including: a fluid jet cutting head manipulable in
space via a multi-axis machine that includes two axes of rotation
that intersect to define a machine focal point, the fluid jet
cutting head including a nozzle from which a high pressure fluid
jet is discharged during operation to process a workpiece; and a
contour follower apparatus comprising a sensor and a gimbal
assembly that includes a swivel arm operable to rotate about a
first axis of rotation and a contact member rotatably coupled to
the swivel arm to rotate about a second axis of rotation which
intersects with the first axis of rotation to define a gimbal
assembly focal point, the contact member including one or more
surface features arranged to ride upon a surface of the workpiece
during operation and to define a reference plane that contains the
gimbal assembly focal point. Advantageously, the sensor operates in
conjunction with the gimbal assembly of the contour follower
apparatus to sense a deviation between the machine focal point and
the gimbal assembly focal point as the contact member rides upon
the surface of the workpiece during operation.
[0016] The fluid jet cutting system may further include a gimbal
mount assembly that couples the gimbal assembly to the multi-axis
machine and is configured to sense a collision event of the gimbal
assembly with another object. The gimbal assembly may be configured
to adjust to changes in topography of the workpiece via rotational
movement of the swivel arm and contact member about the first and
second axes of rotation, respectively, while the gimbal assembly
simultaneously enables sensing of any deviation between the machine
focal point and the gimbal assembly focal point.
[0017] One embodiment of a method of controlling a standoff
distance of a nozzle of a fluid jet cutting head manipulable in
space via a multi-axis machine may be summarized as including:
manipulating the fluid jet cutting head relative to a workpiece to
be processed such that a gimbal assembly associated with the fluid
jet cutting head rides upon a surface of the workpiece, the gimbal
assembly including two axes of rotation that intersect to define a
gimbal assembly focal point; and sensing a deviation between a
machine focal point and the gimbal assembly focal point for
adjusting the standoff distance of the nozzle.
[0018] The method may further include adjusting the standoff
distance of the nozzle toward a state in which the machine focal
point and the gimbal assembly focal point are coincident, or
adjusting the standoff distance of the nozzle toward a state in
which a distance between the machine focal point and the gimbal
assembly focal point is a predetermined value. Sensing the
deviation between the machine focal point and the gimbal assembly
focal point for adjusting the standoff distance of the nozzle may
include sensing a change in distance between the nozzle and the
surface of the workpiece as the contact member rides upon the
surface of the workpiece during operation. In some instances, the
machine focal point and the gimbal assembly focal point may not be
coincident when sensing the deviation or change in distance between
the nozzle and the surface of the workpiece. The gimbal assembly
may include a gimbal base, a swivel arm rotatably coupled to the
gimbal base to rotate about a first axis of rotation, and a contact
member rotatably coupled to the swivel arm to rotate about a second
axis of rotation which intersects with the first axis of rotation
to define the gimbal assembly focal point, the contact member
including one or more surface features arranged to ride upon the
surface of the workpiece during operation and to define a reference
plane that contains the gimbal assembly focal point, and wherein
sensing the deviation between the machine focal point and the
gimbal assembly focal point may include sensing a displacement of
the gimbal base while the gimbal assembly rides on the surface of
the workpiece. Sensing the deviation between the machine focal
point and the gimbal assembly focal point may include allowing the
gimbal assembly to adjust to changes in topography of the workpiece
via rotational movement of a swivel arm and a contact member about
the first and second axes of rotation, respectively. The method may
further include: sensing a collision of the gimbal assembly with
another object; and adjusting operation of the multi-axis machine
in response to the collision. Sensing a collision may include
converting an impact applied to the gimbal assembly during the
collision to vertical movement of a sensor member to generate a
collision event signal.
[0019] One embodiment of a collision detection system for a
multi-axis machine to assist in sensing an impending collision
between a tool of the multi-axis machine and another object may be
summarized as including: a contour follower apparatus configured to
ride upon a surface of the workpiece during operation; and a
collision sensor arrangement operatively coupled to the contour
follower apparatus to sense the impending collision. The collision
sensor arrangement may include a collision sensor and a sensor
member that is constrained such that torque applied to the sensor
member during a collision event is converted to displacement of the
sensor member into engagement with the collision sensor to cause
the collision sensor to generate a collision event signal. The
contour follower apparatus may comprise a gimbal assembly having a
swivel arm operable to rotate about a first axis of rotation and a
contact member rotatably coupled to the swivel arm to rotate about
a second axis of rotation, and the contact member may include one
or more surface features arranged to ride upon the surface of the
workpiece during operation. The collision sensor arrangement may be
located remote from the gimbal assembly so as to not compromise
movement of the gimbal assembly as the gimbal assembly rides on the
workpiece during operation. The collision sensor arrangement may be
part of a gimbal mount assembly that is constrained relative to the
tool to move linearly. The gimbal mount assembly may be configured
to provide a rigid connection between the gimbal assembly and the
multi-axis machine which breaks free during a collision event. The
collision sensor arrangement may further include a seat having a
ramp portion, and the sensor member may be forced to move
vertically by the ramp portion of the seat during the collision
event to cause the collision sensor to generate the collision event
signal. The sensor member may be biased towards the seat.
[0020] One embodiment of a fluid jet cutting system may be
summarized as including: a multi-axis machine; a fluid jet cutting
head manipulable in space via the multi-axis machine, the fluid jet
cutting head including a nozzle from which a high pressure fluid
jet is discharged during operation to process a workpiece; and a
gimbal assembly coupled to the multi-axis machine and being
configured to ride upon a surface of the workpiece in a vicinity of
the nozzle of the fluid jet cutting head during operation. The
fluid jet cutting system may further include a collision sensor
arrangement operatively coupled to the gimbal assembly to sense an
impending collision between the nozzle of the multi-axis machine
and another object.
[0021] One embodiment of a gimbal assembly for a multi-axis machine
to assist in maintaining a spatial relationship between a tool of
the multi-axis machine and a workpiece to be processed by the tool
may be summarized as including: a swivel arm operable to rotate
about a first axis of rotation; and a contact member rotatably
coupled to the swivel arm to rotate about a second axis of
rotation, the contact member including one or more surface features
arranged to ride upon a surface of the workpiece during operation,
and wherein the gimbal assembly enables sensing a change in
distance between the tool and the surface of the workpiece as the
contact member rides upon the surface of the workpiece during
operation.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0022] FIG. 1 is an isometric view of a multi-axis fluid jet
cutting machine, according to one embodiment.
[0023] FIG. 2 is a side elevational view of a portion of the fluid
jet cutting machine of FIG. 1, which includes a cutting head
assembly and a contour follower apparatus associated therewith.
[0024] FIG. 3 is an isometric view of a gimbal assembly of the
contour follower apparatus of FIG. 2 shown with a fluid jet nozzle
(e.g., a mixing tube) of the cutting head assembly.
[0025] FIG. 4 is a partial cross-sectional view of the gimbal
assembly of FIG. 3 revealing internal components and features
thereof.
[0026] FIG. 5 is an isometric view showing the gimbal assembly of
FIG. 3 detached from a portion of a gimbal mount assembly of the
contour follower apparatus of FIG. 2.
[0027] FIG. 6 is an exploded isometric view of the portion of the
gimbal mount assembly shown in FIG. 5.
[0028] FIG. 7 is a partial cross-sectional view of the portion of
the gimbal mount assembly and gimbal assembly shown in FIG. 5
revealing internal components and features thereof.
[0029] FIG. 8 is a partially exploded view of the gimbal mount
assembly with the gimbal assembly attached thereto.
[0030] FIG. 9 is a partial cross-sectional view of the gimbal mount
assembly with the gimbal assembly attached thereto.
[0031] FIG. 10 is an exploded isometric view of the contour
follower apparatus of FIG. 2.
[0032] FIG. 11 is a partial cross-sectional view of the contour
follower apparatus of FIG. 2 with a cover removed to reveal
internal components and features thereof.
[0033] FIG. 12 is a bottom perspective view of a contact member of
a gimbal assembly of a contour follower apparatus, according to
another embodiment.
[0034] FIG. 13 is a bottom perspective view of a contact member of
a gimbal assembly of a contour follower apparatus, according to yet
another embodiment.
DETAILED DESCRIPTION
[0035] In the following description, certain specific details are
set forth in order to provide a thorough understanding of the
various disclosed embodiments. However, one of ordinary skill in
the relevant art will recognize that embodiments may be practiced
without one or more of these specific details. In other instances,
well-known structures associated with fluid jet cutting systems,
other machining systems (e.g., drilling machines, mills, routers)
and methods of operating the same may not be shown or described in
detail to avoid unnecessarily obscuring descriptions of the
embodiments. For instance, it will be appreciated by those of
ordinary skill in the relevant art that a high-pressure fluid
source and an abrasive source may be provided to feed high-pressure
fluid and abrasives, respectively, to a cutting head of the fluid
jet systems described herein to facilitate, for example,
high-pressure or ultrahigh-pressure abrasive fluid jet cutting of
workpieces. As another example, well-known control systems and
drive components may be integrated into the fluid jet cutting
systems and other machines to facilitate movement of the cutting
head or other tool relative to the workpiece to be processed. These
systems may include drive components to manipulate the cutting head
or other tool about multiple rotational and translational axes,
such as, for example, as is common in five-axis positioning
systems.
[0036] Unless the context requires otherwise, throughout the
specification and claims which follow, the word "comprise" and
variations thereof, such as "comprises" and "comprising," are to be
construed in an open, inclusive sense, that is, as "including, but
not limited to."
[0037] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure or
characteristic described in connection with the embodiment is
included in at least one embodiment. Thus, the appearances of the
phrases "in one embodiment" or "in an embodiment" in various places
throughout this specification are not necessarily all referring to
the same embodiment. Furthermore, the particular features,
structures, or characteristics may be combined in any suitable
manner in one or more embodiments.
[0038] As used in this specification and the appended claims, the
singular forms "a," "an," and "the" include plural referents unless
the content clearly dictates otherwise. It should also be noted
that the term "or" is generally employed in its sense including
"and/or" unless the content clearly dictates otherwise.
[0039] Embodiments described herein provide enhanced systems and
methods for maintaining a spatial relationship between a tool of a
multi-axis machine (e.g., a fluid jet nozzle of a fluid jet cutting
machine) and a workpiece to be processed by the tool to improve
performance. Embodiments described herein may also provide enhanced
systems and methods for sensing collisions with an obstruction in
the controlled path of the tool and adjusting operation of the
machine accordingly. Embodiments include, for example, a contour
follower apparatus that operates in conjunction with a cutting head
assembly of a fluid jet cutting machine to ride upon the surface of
a workpiece being cut by the cutting head assembly to provide
standoff distance feedback functionality.
[0040] As described herein, the term cutting head assembly or
cutting head may refer generally to an assembly of components at a
working end of the fluid jet cutting machine, and may include, for
example, an orifice unit and/or nozzle of the fluid jet cutting
system for generating a high-pressure fluid jet and surrounding
structures and devices coupled directly or indirectly thereto to
move in unison therewith. The cutting head assembly or cutting head
may also be referred to as an end effector. Other tools that may be
used in conjunction with the embodiments of the example contour
follower apparatus and related systems and methods described herein
may include end effectors of other types of machines, such as, for
example, tools of multi-axis milling or drilling machines, such as,
for example, drill bits.
[0041] FIG. 1 shows an example embodiment of a fluid jet cutting
system 10. The fluid jet cutting system 10 includes a catcher tank
12 which is configured to support a workpiece 14 on a platform 16
to be processed by the system 10. The catcher tank 12 includes a
volume of water for absorbing energy of the cutting jet during
cutting operations.
[0042] The fluid jet cutting system 10 further includes a bridge
assembly 18 which is movable along a pair of base rails 20, and
straddles the catcher tank 12. In operation, the bridge assembly 18
moves back and forth along the base rails 20 with respect to a
translational axis Y to position a cutting head 22 of the system 10
for processing the workpiece 14. A tool carriage 24 is movably
coupled to the bridge assembly 18 to translate back and forth along
another translational axis X, which is aligned perpendicularly to
the translational axis Y. The tool carriage 24 is further
configured to raise and lower the cutting head 22 along yet another
translational axis Z to move the cutting head 22 toward and away
from the workpiece 14. A manipulable forearm 30 and wrist 34 are
provided intermediate the cutting head 22 and the tool carriage 24
to provide additional functionally.
[0043] More particularly, with reference to FIG. 2, the forearm 30
is rotatably coupled to the tool carriage 24 to rotate the cutting
head 22 about an axis of rotation C and the wrist 34 is rotatably
coupled to the forearm 30 to rotate the cutting head 22 about
another axis of rotation B that is non-parallel to the
aforementioned rotational axis C. In combination, the rotational
axes B, C enable the cutting head 22 to be manipulated in a wide
range of orientations relative to the workpiece 14 to facilitate,
for example, cutting of complex profiles including
three-dimensional shapes.
[0044] With continued reference to FIG. 2, the rotational axes B, C
may converge at a machine focal point 42 which, in some
embodiments, may be offset from the end or tip of a nozzle or
mixing tube 40 of the cutting head 22. The end or tip of the nozzle
or mixing tube 40 of the cutting head 22 is preferably positioned
to maintain a desired standoff distance from the workpiece to be
processed. The standoff distance may be selected to optimize the
cutting performance of the fluid jet, and, in some embodiments, may
be a fixed distance between about 0.010 inches and about 0.100
inches, or in some instances, a fixed distance between about 0.010
inches and about 0.500 inches, such as may be the case when cutting
more convolute or complex shapes where a larger standoff distance
may be required.
[0045] During operation, movement of the cutting head 22 with
respect to each of the translational axes X, Y, Z and rotational
axes B, C may be accomplished by various conventional drive
components and an appropriate control system 28 (FIG. 1) which
includes a configured computing system. Other well-known systems
associated with fluid jet cutting machines may also be provided
such as, for example, a high-pressure or ultrahigh-pressure fluid
source (e.g., direct drive and intensifier pumps with pressure
ratings ranging from 40,000 psi to 100,000 psi and higher) for
supplying high-pressure or ultrahigh-pressure fluid to the cutting
head 22 and/or an abrasive source (e.g., abrasive hopper and
distribution system) for feeding abrasives to the cutting head 22
to enable abrasive fluid jet cutting. In some embodiments, a vacuum
device may be provided to assist in drawing abrasives into the
fluid from the fluid source to produce a consistent abrasive fluid
jet to enable particularly accurate and efficient workpiece
processing. Details of the control system 28, conventional drive
components and other well-known systems associated with fluid jet
cutting systems, however, are not shown or described in detail to
avoid unnecessarily obscuring descriptions of the embodiments.
[0046] Again, embodiments described herein provide enhanced systems
and methods for maintaining a spatial relationship between a tool
of a multi-axis machine (e.g., a fluid jet nozzle or mixing tube 40
of a fluid jet cutting system 10) and a workpiece 14 to be
processed by the tool to improve performance. Embodiments described
herein may also provide enhanced systems and methods for sensing
collisions with an obstruction in the controlled path of the tool
(e.g., nozzle or mixing tube 40) and adjusting operation
accordingly. For instance, an example contour follower apparatus
100 is shown in FIG. 2 and includes a gimbal assembly 102 which
enables sensing of any deviation between a machine focal point 42
associated with a fluid jet nozzle or mixing tube 40 and a gimbal
assembly focal point 104 defined by the gimbal assembly 102 as the
gimbal assembly 102 rides upon the surface of the workpiece 14
during operation. The example contour follower apparatus 100 also
enables sensing of a collision event with an obstruction in the
controlled path of the nozzle or mixing tube 40 for protecting the
nozzle or mixing tube 40 from inadvertent damage. Although
embodiments are discussed herein in terms of high-pressure fluid
jet cutting machines, including abrasive waterjet cutting machines,
one skilled in the relevant art will recognize that aspects and
techniques of the present invention can be applied and used in
connection with various other types of multi-axis machines, such
as, for example, multi-axis CNC milling machines.
[0047] With continued reference to FIG. 2, a cutting head assembly
50 includes the cutting head 22 through which fluid passes during
operation to generate a high-pressure fluid jet for processing the
workpiece 14 which is discharged via an outlet 23 of the cutting
head 22 (e.g., an outlet 23 of the nozzle or mixing tube 40 of the
cutting head 22). The cutting head assembly 50 further includes or
otherwise operates in conjunction with a contour follower apparatus
100 that is attached to the wrist 34 of the multi-axis positioning
system to be manipulated in space with the cutting head 22. As
previously described, the forearm 30 is rotatably coupled to a tool
carriage 24 (FIG. 1) to rotate the cutting head 22 about an axis of
rotation C and the wrist 34 is rotatably coupled to the forearm 30
to rotate the cutting head 22 about another axis of rotation B that
is non-parallel to the aforementioned rotational axis C. In
combination, the rotational axes B, C enable the cutting head 22 to
be manipulated in a wide range of orientations relative to the
workpiece 14 to facilitate, for example, cutting of complex
profiles including three-dimensional shapes.
[0048] With reference to FIGS. 2 and 3, the contour follower
apparatus 100 is provided with a multi-axis gimbal assembly 102,
which includes a gimbal assembly focal point 104 defined by the
intersection of rotational axes A.sub.1, A.sub.2. The gimbal
assembly 102 which is mounted and controlled relative to the nozzle
or mixing tube 40 of the cutting head 22 such that the gimbal
assembly focal point 104 and the machine focal point 42 are
maintained coincident or essentially coincident throughout cutting
of the workpiece 14.
[0049] According to the illustrated embodiment shown in the
figures, the multi-axis gimbal assembly 102 does not incorporate
full semicircular arc movement but rather is configured in such a
way that rotation about the rotational axes A.sub.1, A.sub.2 is
limited to the motion needed for the focal point measurement
functionality described herein. This reduced mobility of the
multi-axis gimbal assembly 102 advantageously avoids problems
associated with jet disruption, accelerated wear, and degradation
of cut quality. The mobility or range of motion of the multi-axis
gimbal assembly 102, however, may be adjusted depending on the
application and functionality desired.
[0050] With reference to FIG. 3, the gimbal assembly 102 includes a
gimbal base 110, a swivel arm 112 rotatably coupled to the gimbal
base to rotate about a first gimbal axis of rotation A.sub.1, and a
contact member 114 rotatably coupled to the swivel arm 112 to
rotate about a second gimbal axis of rotation A.sub.2 which
intersects with the first axis of rotation A1 to define the gimbal
assembly focal point 104. The contact member 114 of the gimbal
assembly 102 includes one or more surface features 116 arranged to
ride upon a surface of the workpiece 14 during operation and to
define a reference plane P that contains the gimbal assembly focal
point 104. During operation, the gimbal assembly 102 enables
sensing of a deviation between the machine focal point 42 and the
gimbal assembly focal point 104 as the contact member 114 rides
upon the surface of the workpiece 14 during operation.
[0051] Rotational motion of the swivel arm 112 about the first
gimbal axis of rotation A.sub.1 and rotational motion of the
contact member 114 about the second gimbal axis of rotation A.sub.2
are driven as a function of the orientation of the reference plane
P, which is defined by contact of the contact member 114 and the
workpiece 14. According to the example embodiment of the contour
follower apparatus 100 shown in the figures, the reference plane P
is defined as a plane that is tangent to a rounded bottom annular
edge or toroid portion 118 that contacts with the surface of the
workpiece 14 during operation. In other instances, a plurality of
projections (e.g., three contact pads spaced regularly or
irregularly about a central axis) or other surface features may
collectively define the plane P. The first gimbal axis A.sub.1 and
the second gimbal axis A.sub.2 are designed to intersect at a point
(i.e., the gimbal assembly focal point 104) within the reference
plane P; however, it is appreciated that, due to manufacturing
tolerances or other factors, the gimbal axes A.sub.1, A.sub.2 may
not necessarily intersect or lie within the plane P exactly.
Ideally, the gimbal axes A.sub.1, A.sub.2 intersect at a point
(i.e., the gimbal assembly focal point 104) within the reference
plane P at a center of an annular portion 120 of the contact member
114. This locates the gimbal assembly focal point 104 in the center
of said annular portion 120 on the surface of the workpiece 14 to
correspond to the location of the machine focal point 42
(illustrated at 0.100'' below the nozzle or mixing tube 40 along
the tool axis A.sub.0) when the machine is controlled to position
the nozzle or mixing tube 40 at the desired standoff distance.
Providing the gimbal assembly 102 with the ability to pivot about
such gimbal axes A.sub.1, A.sub.2 allows the contact member 114 to
conform to any material angle without separating the location of
the machine focal point 42 and the gimbal assembly focal point 104.
This allows the gimbal assembly 102 to be solely driven by the
height of the workpiece terrain at the machine focal point 42,
regardless of approach or departure angles, thereby providing a
direct correlation between the machine focal point 42 and the
surface of the workpiece 14 which can be used with a feedback
control loop to maintain the standoff distance at the desired or
optimum distance.
[0052] The positioning and operation of the gimbal focal point
assembly 102 allows for full and automatic articulation about the
machine focal point 42, however, in order to extract data
pertaining to deviations in the distance between the surface of the
workpiece 14 and the machine focal point 42, the first gimbal axis
A.sub.1 must be fixed in a plane perpendicular to the measurement
axis (i.e., piston axis A.sub.4 shown in FIGS. 5 through 10) while
allowing for rotation about the first gimbal axis A.sub.1 and
translation along the measurement axis (i.e., piston axis A.sub.4
shown in FIGS. 5 through 10), as represented by the arrows labeled
122 in FIG. 3. Keeping free rotation of the gimbal axes A.sub.1,
A.sub.2 allows the contact member 114 to actively follow surface
contours of the workpiece 14. By rigidly connecting the gimbal base
110 to a piston 180 (FIGS. 8 through 11) that is restricted to
linear motion along the piston axis A.sub.4, the first gimbal axis
A.sub.1 is confined in the plane perpendicular to the piston axis
A.sub.4 and allowed to move freely only in the direction of the
piston axis A.sub.4, again as represented by the arrow labeled 122
in FIG. 3. The piston axis A.sub.4 may be aligned parallel with a
tool axis A.sub.0 or may be inclined relative thereto, as can be
appreciated from FIG. 2 wherein the tool axis A.sub.0 and the
piston axis A.sub.4 are slightly inclined relative to each
other.
[0053] With reference now to FIGS. 10 and 11, the piston 180 is
restricted to linear movement by a cage 194 coupled to an upper end
of the piston 180. According to the illustrated embodiment, the
cage 194 includes a plurality of bearings 195 that engage a
corresponding plurality of linear guide shafts 196 fixed within a
housing 190 of the contour follower apparatus 100 which
accommodates the piston 180. This restricts the piston 180 to
bidirectional movement parallel to the linear guide shafts 196
along the piston axis A.sub.4. This restriction in movement allows
the gimbaled movement of the contact member 114 to operate
independently from the overall vertical displacement of the gimbal
assembly 102 (which may arise from a deviation of the surface of
the workpiece 14 from what is expected when generating the tool
path). In other words, the orientation of the contact member 114 in
space is independent of the bidirectional linear movement of the
piston 180. By extension, the contact member 114 of the gimbal
assembly 102 serves to rigidly support the full weight of the
piston 180 on the surface of the workpiece 14. Due to this
relationship between the piston 180, the bearing cage 194 and the
gimbal assembly 102, the gimbal assembly 102 automatically
compensates for any changes of material angle through rotation of
the gimbal axes A.sub.1, A.sub.2 without moving the piston 180. The
gimbal assembly 102 only forces the piston 180 to move if the
surface of the workpiece 14 varies in such a way to change the
relative location of the gimbal assembly focal point 104 from the
machine focal point 42, such as may be the case when the workpiece
14 deviates from an expected or nominal state due to warpage of the
workpiece or otherwise.
[0054] With reference to FIG. 10, movement of the piston 180 may be
measured along the piston axis A.sub.4 via a rack and pinion
assembly comprising a gear rack 182 and spur gear 184. The gear
rack 182 is mounted to the piston 180 and the spur gear 184 is
mounted to a rigidly mounted rotary encoder 186 in the housing 190
that converts or correlates a rotational position of the pinion
gear 184 to a linear measurement which may then be used in a
feedback control system to move the cutting head 22 back toward a
state in which the machine focal point 42 is coincident with the
gimbal assembly focal point 104. Various feedback control
mechanisms, such as a PID control loop feedback mechanism, may be
used to maintain the machine focal point 42 and the gimbal assembly
focal point 104 coincident or nearly coincident thereby ensuring a
precise standoff distance of the nozzle or mixing tube 40 from the
surface of the workpiece 14.
[0055] Further details of the example embodiment of the contour
follower apparatus 100 and components thereof will now be described
with reference to FIGS. 4 through 11.
[0056] With reference to FIG. 4, the contact member 114 of the
gimbal assembly 102 rides on the surface of the workpiece 14 to be
processed and translates any deviations up through a rotary shaft
124 which may be pressed into, threaded into or otherwise coupled
to the contact member 114. The rotary shaft 124 is configured to
rotate within rotational bearings 126 (e.g., rolling element
bearings such as ball bearings) that are provided within a distal
end 128 of the swivel arm 112. Rotational motion of the contact
member 114 about the second gimbal axis A.sub.2 may be restricted
via a rotation stop 130 (FIG. 7) provided in the contact member 114
that interacts with stop features 132 (FIG. 7) at the distal end
128 of the swivel arm 112 to limit rotational motion within
predetermined limits. In this manner, the contact member 114 may be
limited, for example, to rotate or pivot back and forth less than
ninety degrees or less than forty-five degrees. The bearings 126
within the distal end 128 of the swivel arm 112 may be protected
from contamination at each of opposing sides of the swivel arm 112
with a face seal 134 and a threaded end cap 136 sealed with an
o-ring 138, respectively.
[0057] With continued reference to FIG. 4, movement of the contact
member 114 is further translated through the swivel arm 112 to
another rotary shaft 140 which may be pressed into, threaded into,
or otherwise coupled to a proximal end 129 of the swivel arm 112 to
rotate within the gimbal base 110. The rotary shaft 140 may be
protected and guided by a similar arrangement of bearings 144, face
seal 146, and threaded end cap 148 with o-ring 150. Additionally,
an end of the rotary shaft 140 may comprise a piston element 142
with an o-ring 143 that allows pneumatic pressure applied within an
internal cavity 145 of the gimbal base 110 to force a face of the
piston element 142 against a shoulder 152 within an inner bore 154
of the gimbal base 110 to provide a swivel lock that prevents any
rotational motion of the swivel arm 112 relative to the gimbal base
110 upon application of such pneumatic pressure. In this manner,
motion of the gimbal assembly 102, in particular the swivel arm
112, can be selectively constrained when it is desired not to use
the gimbal assembly 102 while cutting a portion of the workpiece
14. More particularly, pressurized air may be supplied on demand to
the internal cavity 145 to urge the face of the piston element 142
into the shoulder 152 via a hollow stem 159 that is pressed into or
otherwise coupled to the gimbal base 110 in fluid communication
with the internal cavity 145. Additionally, a rotation stop 156 may
be provided at the proximal end 129 of the swivel arm 112 to engage
stop features 158 provided in the gimbal base 110 to ensure any
travel abnormal to the desired operation is restricted between the
swivel arm 112 and the gimbal base 110. In this manner, the swivel
arm 112 may be limited, for example, to rotate or pivot back and
forth less than ninety degrees or less than forty-five degrees.
[0058] With reference to FIG. 5, the gimbal base 110 may include a
coupling arrangement 160 for providing quick connect and disconnect
functionality between the gimbal assembly 102 and a remainder of
the contour follower apparatus 100, including a gimbal mount
assembly 103 (FIG. 8) comprising a torque transmitter assembly 105
and a piston assembly 106. The coupling arrangement 160 may include
one or more dowel pins 162 or other alignment devices and one or
more magnetic devices 164. The dowel pins 162 or other alignment
devices allow any torque or translation experienced by the contact
member 114 to be transmitted through to the mating assembly (i.e.,
torque transmitter assembly 105) without straining the magnetic
devices 164. The magnetic devices 164 largely assist in preventing
the pneumatic pressure, when applied to the internal cavity 145,
from breaking the mechanical connection between the gimbal base 110
and an associated gimbal mount 171 of the torque transmitter
assembly 105.
[0059] With reference to FIGS. 5 through 8, the gimbal assembly 102
of the example contour follower apparatus 100 may be joined to a
base 170 of the torque transmitter assembly 105 via the
aforementioned coupling arrangement 160. The magnetic devices 164
and dowel pins 162 or other alignment devices may be used to align
the hollow stem 159 within a check valve 172 that is provided in
the base 170 of the torque transmitter assembly 105, as shown best
in FIG. 7. The connection between the stem 159 and the check valve
172 provides an open air passage between a pneumatic source 174 and
the gimbal assembly 102 for selectively preventing rotational
motion of the swivel arm 112 as previously described. The
configuration of the check valve 172 allows a check valve ball 176
to block the air supply to the gimbal assembly 102 if the stem 159
should fail to seal, or in the event the gimbal assembly 102 is
removed. The base 170 of the torque transmitter assembly 105
translates any motion from the gimbal assembly 102 through the
aforementioned piston 180 which has the gear rack 182 attached
thereto, which in turn drives the spur gear 184 (FIG. 10) coupled
to the rotary encoder 186 (FIG. 10) in order to quantify the linear
motion for feedback control.
[0060] With reference to FIGS. 10 and 11, a piston gimbal assembly
169 including the gimbal assembly 102, the torque transmitter
assembly 105, and the piston assembly 106 installs into a housing
190. The gear rack 182, which is fixed to the piston 180, meshes
with the spur gear 184 that is attached to the rotary encoder 186.
The rotary encoder 186 is held static within the housing 190 via an
encoder mounting bracket 201 which creates a reference frame from
which to base all movements of the piston gimbal assembly 169. The
rotary encoder 186 tracks the rotation of the spur gear 184 to
extrapolate the linear motion of the gear rack 182. Motion of the
gear rack 182 is constrained to translate parallel to the piston
axis A.sub.4 and linear guide shafts 196 via the bearing cage 194.
The bearing cage 194 is secured to the piston 180 and confines all
linear movement along piston axis A.sub.4, which is perpendicular
to an axis of the rotary encoder 186. This linear movement can
either be driven by the gimbal assembly 102 following the surface
of the workpiece 14 or, alternatively, a commanded retraction of a
pneumatic cylinder 200 or other actuator provided in the housing
190. The pneumatic cylinder 200 or other actuator may be connected
to the encoder mounting bracket 201 via a separate mounting plate
202. The pneumatic cylinder 200 or other actuator may be operable
to lift the gimbal assembly 102 by rotating a torque arm 203 that
raises the bearing cage 194, thereby raising the piston assembly
106 and the gimbal assembly 102. In this manner, the gimbal
assembly 102 may be deployed and retracted into and out of an
active configuration.
[0061] With reference to FIG. 10, internal components within the
housing 190 may be protected by a sealed housing cap 191. In
addition, the interface between the housing 190 and the torque
transfer assembly 105 may be protected from the environment by a
bellows assembly 193 which allows for extension and retraction of
the gimbal assembly 102 relative to the housing 190.
[0062] With reference back to FIG. 2, the contour follower
apparatus 100 may be coupled to the wrist 34 of the fluid jet
cutting system 10 via a series of mounting brackets 206, 207, 208.
For example, the wrist 34 may be outfitted with a motor bracket 206
allowing for the installation of a mounting bracket 207, and an
adjustment bracket 208 may be utilized to connect the contour
follower apparatus 100 to the mounting bracket 207. The adjustment
bracket 208 may provide a variable mounting location that allows
for the gimbal assembly focal point 104 of the contour follower
assembly 102 to be adjusted to be coincident with the machine focal
point 42.
[0063] The example contour follower apparatus 100 shown in the
figures may also provide enhanced systems and related methods for
sensing collisions of the tool (e.g., nozzle or mixing tube 40) or
associated components with an obstruction in the controlled path of
the tool and adjusting operation of the machine accordingly. As
previously described, the contact member 114 of the gimbal assembly
102 is centered on the machine focal point 42 which keeps the
nozzle or mixing tube 40 centered within the contact member 114.
Accordingly, an obstruction, such as a workpiece clamp or a piece
of raised material, is most likely to contact the contact member
114 before contacting the nozzle or mixing tube 40. Because the
contact member is positioned away from the nozzle or mixing tube
40, any strike that would endanger the nozzle or mixing tube 40
creates a torque on the contact member 114 and gimbal assembly 102
before reaching the nozzle or mixing tube 40. With reference to
FIGS. 5 through 9, this torque is utilized to turn a pin 181 (or
other sensor member) within a seat having a "V" shaped or other
appropriately shaped (e.g., cone shaped) ramp portion 183 in order
to translate rotational or transverse forces into vertical motion
of the pin 181. Vertical motion of the pin 181 of sufficient
magnitude results in contact of the pin 181 with a limit switch
214, which in turn generates a collision event signal. When a
collision is not being sensed, the pin 181 must stay located firmly
within the "V" shaped or other appropriately shaped ramp portion
183 of the seat to allow a rigid connection to be simulated. This
is accomplished by providing a spring 177 between the "V" shaped or
other appropriately shaped ramp portion 183 of the seat and the
base 170 of the torque transmitter assembly 105. A specially shaped
spring washer 178 is located at the end of the spring 177 to ensure
omnidirectional strikes compress the spring axially to ensure full
spring resistance force. Full spring resistance force is desired to
minimize or eliminate false triggers that may otherwise arise from
having a cantilevered load applied to the spring 177.
[0064] With reference to FIGS. 6 and 7, the base 170 of the torque
transmitter assembly 105 contains a gimbal mount 171 to interface
with the gimbal assembly 102. The base 170 also includes a
pneumatic fitting 175 to supply pressurized air to the check valve
172. The check valve 172 houses a check ball 176 in order to seal
off airflow when the gimbal assembly 102 is not connected. The
gimbal mount 171 is connected to the base 170 of the torque
transmitter assembly 105 via two fasteners 168 that are designed to
shear in the event of a catastrophic collision. The gimbal mount
171 houses two magnetic devices 165 for mating with the
corresponding magnetic devices 164 in the gimbal base 110 of the
gimbal assembly 102 and includes a plurality of apertures 163 to
accept and align with the corresponding dowel pins 162 or other
alignment features of the gimbal assembly 102. The compression
spring 177, spring washer 178, and a collision sensor base 179 are
all sandwiched between the base 170 of the torque transmitter
assembly 105 and the collision sensor pin 181. The compression
spring 177 forces the collision sensor pin 181 to positively lock
into the "V" shaped or other appropriately shaped ramp portion 183
of the seat within the collision sensor base 179. The spring washer
178 ensures all loading to the compression spring 177 is applied
axially, ensuring full spring resistance force regardless of the
force application vector during a collision event. The "V" shaped
or other appropriately shaped ramp portion 183 of the seat within
the collision sensor base 179 converts relative rotary or
transverse motion between the collision sensor pin 181 and the
collision sensor base 179 into vertical motion and ensures that the
collision sensor pin 181 automatically returns to its original
location after clearance of the obstruction associated with the
collision. The rotary motion between the base 170 of the torque
transmitter assembly 105 and the collision sensor pin 181 is locked
together via a keyed bore 187 and correspondingly shaped portion
185 of the collision sensor pin 181, which may be held in place by
a fastener 188 and protected from the environment through the use
of a suitable washer 189 (e.g., a Teflon washer). The collision
sensor base 179 is prevented from rotating by being fixed to the
piston assembly 106 that is constrained to move bi-directionally
along the piston axis A.sub.4.
[0065] With reference to FIG. 8, the gimbal assembly 102 and torque
transmitter assembly 105 is coupled to the piston assembly 106. The
piston assembly 106 includes two compression springs 210 that force
a limit switch housing 212, which contains the limit switch 214, to
bottom out on the torque transmitter assembly 105. The compression
springs 210 enable the limit switch housing 212 to travel upward
beyond the trigger point of the limit switch 214 in the case of a
catastrophic collision. The limit switch 214 is recessed within the
limit switch housing 212 so that the natural state of the limit
switch 214 is untouched by the torque transmitter assembly 105.
Thus, it is only during a collision that the limit switch 214 is
engaged by the torque transmitter assembly 105. As previously
described, the piston assembly 106 is received in the housing 190
and constrained to move bi-directionally by an assembly of linear
guide shafts 196 that guide a bearing cage 194 which attaches to
the piston 180. The interaction of the bearing cage 194 and linear
guide shafts 196 restricts any rotational motion of the collision
sensor base 179 which, upon a collision, creates the relative
linear motion of the pin 181 required to engage the limit switch
214 as the pin 181 is driven into the "V" shaped or other
appropriately shaped ramp portion 183 of the seat. In this manner,
the example embodiment of the contour follower apparatus 100 can
provide collision detection functionality without compromising the
dynamics of the gimbal assembly 102 which advantageously provides
feedback control functionality for precisely maintaining standoff
distance of the nozzle or mixing tube 40 to enhance system
performance.
[0066] FIGS. 12 and 13 show other example embodiments of contact
members 314, 414 that may be used with the aforementioned gimbal
assembly 102 shown in FIGS. 1 through 11 in lieu of contact member
114. The contact member 314 shown in FIG. 12 includes an annular
base 316 and a slide member 318 removably coupleable to the annular
base 316 to provide an interchangeable element that may be replaced
when worn or when otherwise desired. The slide member 318 may be
formed of a material (e.g., UHMW) that provides a low friction
interface for sliding smoothly on the surface of a workpiece during
a cutting operation. The slide member 318 may include scallops 320,
indentations or other features which facilitate intermittent
contact with the workpiece and which allow water spray, abrasives
and other matter to exit through the scallops 320, indentations or
other features to prevent pooling and/or hydroplaning which may
otherwise disrupt or impact standoff distance feedback
functionality provided by the contact member 314. The slide member
318 may include one or more coupling features 322 (e.g., resilient
tabs or clips) for engaging corresponding coupling features 324
(e.g., a groove) of the annular base 316 so that the slide member
318 can be firmly attached to the annular base 316. The contact
member 414 shown in FIG. 13 includes an annular base 416 and an
arrangement of brush elements 418 that collectively define an
interface for riding on the surface of a workpiece during a cutting
operation. The brush elements 418 may be flexible and resilient and
may be spaced apart from each other to allow water spray, abrasives
and other matter to pass between the brush elements 418 to prevent
pooling or other interference with the standoff distance feedback
functionality provided by the contact member 414. The contact
members 314, 414 shown in FIGS. 12 and 13 may be sized and shaped
such that each may directly replace the contact member 114 shown in
the example embodiment of FIGS. 1 through 11 without changing the
location of the plane P defined by the contact interface of said
contact members 314, 414 relative to the remainder of the gimbal
assembly 102 to which it attaches. Accordingly, it is appreciated
that a wide variety of contact members 114, 314, 414 may be
interchangeably used in connection with the apparatuses, systems
and related methods described herein.
[0067] In accordance with the example embodiment of the contour
follower apparatus 100 and related components and sub-assemblies
described herein, related methods of controlling a standoff
distance of a tool (e.g., a nozzle or mixing tube 40 of a fluid jet
cutting head 22) manipulable in space via a multi-axis machine
having two axes of rotation B, C that intersect to define a machine
focal point 42 may be provided. For instance, in some embodiments,
a method of controlling a standoff distance of a nozzle or mixing
tube 40 of a fluid jet cutting head 22 manipulable in space via a
multi-axis machine having two non-parallel and non-orthogonal axes
of rotation B, C that intersect to define a machine focal point 42
may be provided which includes: manipulating the fluid jet cutting
head 22 relative to a workpiece 14 to be processed such that a
gimbal assembly 102 associated with the fluid jet cutting head 22
rides upon a surface of the workpiece 14, the gimbal assembly 102
including two axes of rotation A.sub.1, A.sub.2 that intersect to
define a gimbal assembly focal point 104, and sensing a deviation
between the machine focal point 42 and the gimbal assembly focal
point 104 for adjusting the standoff distance of the nozzle or
mixing tube 40. The method may further include adjusting the
standoff distance of the nozzle or mixing tube 40 toward a state in
which the machine focal point 42 and the gimbal assembly focal
point 104 are coincident, such as, for example, by adjusting the
cutting head 22 along the translational axis Z to move the cutting
head 22 toward and away from the workpiece 14 in response to the
sensed deviation. This may include various feedback control
mechanisms, such as a PID control loop feedback mechanism, to
maintain the machine focal point 42 and the gimbal assembly focal
point 104 coincident or nearly coincident via Z-axis adjustments
(and/or other movements of the other axes X, Y, B, C of the
machine), thereby ensuring a precise standoff distance of the
nozzle or mixing tube 40 from the surface of the workpiece 14.
[0068] In some instances, the gimbal assembly 102 may comprise a
gimbal base 110, a swivel arm 112 rotatably coupled to the gimbal
base 110 to rotate about a first axis of rotation A.sub.1, and a
contact member 114 rotatably coupled to the swivel arm 112 to
rotate about a second axis of rotation A.sub.2 which intersects
with the first axis of rotation A.sub.1 to define the gimbal
assembly focal point 104, and the contact member 114 may include
one or more surface features 116 arranged to ride upon the surface
of the workpiece 14 during operation and to define a reference
plane P that contains the gimbal assembly focal point 104. In such
instances, sensing the deviation between the machine focal point 42
and the gimbal assembly focal point 104 may include sensing a
linear displacement of the gimbal base 110 while the gimbal
assembly 102 rides on the surface of the workpiece 14. In addition,
sensing the deviation between the machine focal point 42 and the
gimbal assembly focal point 104 may include allowing the gimbal
assembly 102 to adjust to changes in topography of the workpiece 14
via rotational movement of the swivel arm 112 and contact member
114 about the first and second axes of rotation A.sub.1, A.sub.2,
respectively.
[0069] According to some embodiments, the method of controlling the
standoff distance of the tool (e.g., nozzle or mixing tube 40) with
the gimbal assembly 102 may further include sensing a collision of
the gimbal assembly 102 with another object and adjusting operation
of the multi-axis machine in response to the collision (e.g.,
shutting down the machine or controlling movement to minimize or
eliminate the impact of the collision). In some instances, sensing
the collision includes converting an impact applied to the gimbal
assembly 102 during the collision to vertical movement of a sensor
member (e.g., sensor pin 181) to generate a collision event
signal.
[0070] Although certain specific details are shown and described
with reference to the example embodiment of the contour follower
apparatus 100 and components and sub-assemblies thereof shown in
FIGS. 2 through 11, one skilled in the relevant art will recognize
that other embodiments may be practiced without one or more of
these specific details. For example, one or more embodiments of a
contour follower apparatus may lack collision detection
functionality altogether. In addition, embodiments of other contour
follower apparatuses may lack the piston 180 and associated rack
182, spur gear 184 and rotary encoder 186 for sensing the linear
displacement of the gimbal base 110 to detect any deviation of the
gimbal assembly focal point 104 from the machine focal point 42.
Instead, rotary encoders may be mounted to the gimbal axes A.sub.1,
A.sub.2 such that the exact orientation of the contact member 114
can be calculated. Such calculations enable a surface of the
workpiece 14 to be located, both in space and orientation, upon
contact of the contact member 114 with the surface of the workpiece
14. Finding the surface location and orientation in this way would
allow for reduced complexity and increased machining
capabilities.
[0071] In addition, although the example embodiment of the gimbal
assembly 102 shown in the figures includes two gimbal axes A.sub.1,
A.sub.2, it is appreciated that a gimbal assembly with more than
two gimbal axes may be provided.
[0072] Although embodiments are described herein in the context of
maintaining a desired a standoff distance between a nozzle or
mixing tube 40 of a fluid jet cutting system 10 and a workpiece 14,
it is appreciated that aspects of the systems and methods described
herein may be used to maintain a tool (e.g., a router bit) at a
desired depth of engagement with a workpiece 14 during a machining
operation.
[0073] Still further, although embodiments are described herein in
the context of maintaining a fixed or consistent standoff distance,
it is appreciated that the systems and methods described herein may
be used to dynamically control the standoff distance throughout at
least a portion of a cutting operation. For example, during certain
activities, such as when piercing a workpiece with a fluid jet, it
may be advantageous to vary the standoff distance as the material
of the workpiece is pierced. The systems and methods described
herein may provide a standoff distance feedback loop to control the
standoff distance accordingly.
[0074] Additionally, although embodiments are described herein in
the context of maintaining a fixed or consistent standoff distance
by adjusting the machine focal point 42 to be coincident or nearly
coincident with the gimbal assembly focal point 104, it is
appreciated that in some embodiments the standoff distance of the
nozzle may be adjusted toward a state in which a distance between
the machine focal point 42 and the gimbal assembly focal point 104
is a predetermined value. For example, it may be advantageous
during some cutting operations to maintain the machine focal point
42 at a predetermined distance above the gimbal assembly focal
point 104 and hence surface of the workpiece 14 for at least a
portion of the cutting operation.
[0075] It is also appreciated that aspects of the gimbal assembly
102 and related methodology described herein may be used in
connection with a wide range of multi-axis machines, including
those which lack a machine focal point altogether.
[0076] Moreover, aspects and features of the various embodiments
described above can be combined to provide further embodiments. All
of the U.S. patents, U.S. patent application publications, U.S.
patent applications, foreign patents, foreign patent applications
and non-patent publications referred to in this specification
and/or listed in the Application Data Sheet are incorporated herein
by reference, in their entirety. Aspects of the embodiments can be
modified, if necessary to employ concepts or features of the
various patents, applications and publications to provide yet
further embodiments.
[0077] These and other changes can be made to the embodiments in
light of the above-detailed description. In general, in the
following claims, the terms used should not be construed to limit
the claims to the specific embodiments disclosed in the
specification and the claims, but should be construed to include
all possible embodiments along with the full scope of equivalents
to which such claims are entitled.
* * * * *