U.S. patent application number 15/385684 was filed with the patent office on 2018-06-21 for deep rolling tool and method.
The applicant listed for this patent is United Technologies Corporation. Invention is credited to Patrick Louis Clavette, Tahany Ibrahim El-Wardany, Robert E. Erickson, Thomas J. Garosshen, Justin R. Hawkes, Michael A. Klecka, Andrzej Ernest Kuczek, Adam S. Meusel, Joseph C. Rampone, Randy P. Salva, Joseph B. Wysocki.
Application Number | 20180171448 15/385684 |
Document ID | / |
Family ID | 60569722 |
Filed Date | 2018-06-21 |
United States Patent
Application |
20180171448 |
Kind Code |
A1 |
Hawkes; Justin R. ; et
al. |
June 21, 2018 |
DEEP ROLLING TOOL AND METHOD
Abstract
An embodiment of a tool assembly includes a robotic assembly, a
tool mount, and a non-axisymmetric deep rolling tool. The robotic
assembly includes a plurality of linear arms connected in series
between a base end and a working end. Adjacent ones of the
plurality of arms are connected via a corresponding plurality of
multi-axis joints such that the working end is articulated by
movement of one or more of the plurality of arms relative to one or
more of the plurality of multi-axis joints. The tool mount is
connected to one of the linear arms or one of the multi-axis joints
at the working end of the robotic assembly. The non-axisymmetric
deep rolling tool is connected to the tool mount, and includes a
spring-loaded shaft assembly disposed along a first axis. A hub has
an upper hub portion adjacent to the distal end of the
spring-loaded shaft assembly aligned with the first axis, and a
lower hub portion extending along a second axis, forming a nonzero
angle relative to the first axis. A roller disk is joined to the
lower portion of the hub and is rotatable about the second axis
parallel to the second portion of the hub.
Inventors: |
Hawkes; Justin R.;
(Marlborough, CT) ; Rampone; Joseph C.;
(Colchester, CT) ; Kuczek; Andrzej Ernest;
(Bristol, CT) ; El-Wardany; Tahany Ibrahim;
(Bloomfield, CT) ; Salva; Randy P.; (Baltic,
CT) ; Clavette; Patrick Louis; (Simsbury, CT)
; Garosshen; Thomas J.; (Glastonbury, CT) ;
Meusel; Adam S.; (Newington, CT) ; Klecka; Michael
A.; (Coventry, CT) ; Erickson; Robert E.;
(Storrs, CT) ; Wysocki; Joseph B.; (Somers,
CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
United Technologies Corporation |
Farmington |
CT |
US |
|
|
Family ID: |
60569722 |
Appl. No.: |
15/385684 |
Filed: |
December 20, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C21D 7/02 20130101; B24B
27/0038 20130101; B21H 7/16 20130101; B21B 37/58 20130101; B21B
27/02 20130101; C22F 1/04 20130101; B24B 39/00 20130101; B23P 9/02
20130101; C21D 7/08 20130101 |
International
Class: |
C22F 1/04 20060101
C22F001/04; B21H 7/16 20060101 B21H007/16; B21B 37/58 20060101
B21B037/58; B21B 27/02 20060101 B21B027/02 |
Claims
1. A tool assembly comprising: a robotic assembly including a
plurality of linear arms connected in series between a base end and
a working end, adjacent ones of the plurality of arms connected via
a corresponding plurality of multi-axis joints such that the
working end is articulated by movement of one or more of the
plurality of arms relative to one or more of the plurality of
multi-axis joints; a tool mount connected to an arm or a multi-axis
joint at the working end of the robotic assembly; and a
non-axisymmetric deep rolling tool connected to the tool mount, the
non-axisymmetric deep rolling tool comprising: a spring-loaded
shaft assembly disposed along a first axis; a hub connected to a
distal end of the spring-loaded shaft assembly, the hub having an
upper hub portion adjacent to the distal end of the spring-loaded
shaft assembly aligned with the first axis, and a lower hub portion
extending along a second axis, the second axis forming a nonzero
angle relative to the first axis; and a roller disk joined to the
lower portion of the hub, the roller disk having a working surface
about its perimeter and being rotatable about the second axis
parallel to the second portion of the hub.
2. The assembly of claim 1, wherein the spring-loaded shaft
assembly comprises a flexible shaft.
3. The assembly of claim 1, wherein the spring-loaded shaft
assembly comprises: a rigid shaft; and a resilient element disposed
at a distal end of the spring-loaded shaft assembly proximate to
the hub.
4. The assembly of claim 3, wherein the rigid shaft is supported by
a linear bearing arranged along the first axis.
5. The assembly of claim 3, wherein the resilient element comprises
a plurality of stacked Belleville washers.
6. The assembly of claim 1 and further comprising: a load cell
disposed along the first axis, the load cell adapted to measure a
force applied along the shaft between a proximal end of the shaft
assembly and the roller disk.
7. The assembly of claim 3, wherein the load cell is contiguous
with the resilient element.
8. The assembly of claim 7, wherein the load cell is in
communication with a monitor adapted to receive signals
corresponding to an instantaneous load on the resilient
element.
9. The assembly of claim 8, wherein the monitor is part of a
controller for the robotic arm with closed-loop feedback logic, the
controller adapted to vary a downward force applied by the robotic
arm to the tool along the first axis based on one or more of the
received signals.
10. The assembly of claim 1, wherein the working surface of the
roller disk includes a profile along its width such that an
effective radius of the roller disk varies along a width
thereof.
11. A method comprising: supporting a workpiece in a fixture, the
workpiece having a first nonplanar surface: and performing a first
rolling operation on the first nonplanar surface, the first rolling
operation comprising: operating a robotic assembly to apply a
downward force over a rolling path of a non-axisymmetric deep
rolling tool, the downward force is applied to a proximal end of a
spring-loaded tool shaft aligned with a first axis, such that the
downward force is transferred through the shaft to a hub disposed
at a distal end of the shaft assembly; and transmitting the
transferred downward force from an upper portion of the hub aligned
with the first axis to a lower portion of the hub parallel to a
second axis, the second axis forming a nonzero angle relative to
the first axis, about which a roller disk is supported by one or
more bearings, such that a resulting compressive force is applied
to the first nonplanar surface of the workpiece via a working
surface of the roller disk; wherein the robotic assembly comprises
a plurality of linear arms connected in series between a base end
and a working end, adjacent ones of the plurality of arms connected
via a corresponding plurality of multi-axis joints such that the
working end is articulated by movement of one or more of the
plurality of arms relative to one or more of the plurality of
multi-axis joints.
12. The method of claim 11, wherein the working surface includes a
profile along its width such that an effective radius of the roller
disk varies along a width thereof, such that the resulting
compressive force applied to the first nonplanar surface varies
along the width of the working surface.
13. The method of claim 12, wherein the working surface of the
roller disk is crowned from a center to opposing first and second
edges.
14. The method of claim 11, wherein the deep rolling tool shaft
comprises: a rigid shaft extending along the first axis; and a
resilient element disposed at a distal end of the rigid shaft
adjacent to the hub.
15. The method of claim 11, and further comprising: operating a
load cell disposed along the first axis to generate signals
corresponding to an instantaneous load on the spring-loaded tool
shaft.
16. The method of claim 15, and further comprising: transmitting
the signals to a controller for monitoring the applied compressive
forces during the first rolling operation
17. The method of claim 11, and further comprising: varying the
downward force of the robotic arm based on the signals generated by
the load cell such that the resulting compressive force is within a
predetermined range along a tool rolling path.
18. The method of claim 11, and further comprising using the tool
to perform a second rolling operation on a second nonplanar surface
of the workpiece.
19. The method of claim 18, wherein the workpiece comprises a fan
blade for a gas turbine engine.
20. The method of claim 19, wherein the first nonplanar surface
includes a junction between an airfoil and a dovetail root.
Description
BACKGROUND
[0001] The disclosed subject matter relates generally to materials
processing, and more specifically to apparatus and methods for deep
rolling metals to induce compressive stresses.
[0002] A low plasticity burnishing (LPB) process can be used on
aluminum fan blade roots to improve damage tolerance from e.g.,
corrosion. This can increase fatigue life or maintain fatigue life
in the presence of damage (e.g., corrosion pits).
[0003] Known LPB tools for complex geometries utilize a ball
bearing at the end of an axisymmetric, hydraulically actuated
shaft. However, this tool is expensive and it involves complex
processing steps. Further, despite its relatively high precision,
the small surface area of a ball bearing unnecessarily slows
production time and throughput. These known tools also cannot be
readily used with widely available machine tools due to the need to
maintain and constantly adjust hydraulic pressure on the bearing
surface.
[0004] An alternative process includes deep rolling process, which
can induce high compressive stresses up to 1.5 mm depth from the
surface of a material through localized plastic deformation to
prevent corrosion pits, foreign object damage, crack initiation,
etc..
[0005] Known deep rolling tools available in the market are usually
used for simple geometries In addition, these tools are expensive
may involve complex processing steps, and is sometimes difficult to
use for thin walls or complex shapes that require five and six axes
deep rolling paths and can be easily achieved using robotic
arrangements.
[0006] Controlling the contact stress between the roller and
material being processed is important to achieving desired
improvements in material properties. With insufficient contact
stress, little or no improvement will be achieved. In addition,
there is also a need to customize the applied load and consequently
the contact stress along the deep rolling path. Too high of a
contact stress can damage the material on/near the surface
resulting in a decrement in properties.
SUMMARY
[0007] An embodiment of a tool assembly includes a robotic
assembly, a tool mount, and a non-axisymmetric deep rolling tool.
The robotic assembly includes a plurality of linear arms connected
in series between a base end and a working end. Adjacent ones of
the plurality of arms are connected via a corresponding plurality
of multi-axis joints such that the working end is articulated by
movement of one or more of the plurality of arms relative to one or
more of the plurality of multi-axis joints. The tool mount is
connected to one of the linear arms or one of the multi-axis joints
at the working end of the robotic assembly. The non-axisymmetric
deep rolling tool is connected to the tool mount, and includes a
spring-loaded shaft assembly disposed along a first axis. A hub is
connected to a distal end of the spring-loaded shaft assembly. The
hub has an upper hub portion adjacent to the distal end of the
spring-loaded shaft assembly aligned with the first axis, and a
lower hub portion extending along a second axis. The second axis
forms a nonzero angle relative to the first axis. A roller disk is
joined to the lower portion of the hub. The roller disk has a
working surface about its perimeter and is rotatable about the
second axis parallel to the second portion of the hub.
[0008] An embodiment of a method includes supporting a workpiece in
a fixture, the workpiece having a first nonplanar surface. A first
rolling operation is performed on the first nonplanar surface, the
first rolling operation including operating a robotic assembly to
apply a downward force over a rolling path of a non-axisymmetric
deep rolling tool. The downward force is applied to a proximal end
of a spring-loaded tool shaft aligned with a first axis, such that
the downward force is transferred through the shaft to a hub
disposed at a distal end of the shaft assembly. The transferred
downward force is transmitted from an upper portion of the hub
aligned with the first axis to a lower portion of the hub parallel
to a second axis. The second axis forms a nonzero angle relative to
the first axis, about which a roller disk is supported by one or
more bearings. A resulting compressive force is applied to the
first nonplanar surface of the workpiece via a working surface of
the roller disk. The robotic assembly includes a plurality of
linear arms connected in series between a base end and a working
end, adjacent ones of the plurality of arms connected via a
corresponding plurality of multi-axis joints such that the working
end is articulated by movement of one or more of the plurality of
arms relative to one or more of the plurality of multi-axis
joints.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of a dovetail root portion of a
gas turbine engine blade.
[0010] FIG. 2 shows a roller processing a workpiece such as a blade
root shown in FIG. 1.
[0011] FIG. 3 is a perspective view of an embodiment of a deep
rolling tool.
[0012] FIG. 4 is an exploded view of the deep rolling tool
embodiment in FIG. 3.
[0013] FIG. 5 shows an embodiment of a deep rolling tool attached
to a robot arm for accessing difficult to process areas of a
workpiece with the deep rolling tool.
DETAILED DESCRIPTION
[0014] Generally, a roller disk with a crowned or otherwise
nonplanar working surface about its perimeter can be attached to an
end of a spring loaded shaft. The tool can be attached to a device
to process one or more parts. The tool uses multiple tool passes to
induce residual compressive stresses while maintaining the
appropriate level or range of contact stresses at the roller's
point of contact via selective spring loading of the tool.
[0015] FIG. 1 shows workpiece 10, which can be supported in a
suitable fixture (not shown). Workpiece 10 has airfoil 12 and
dovetail root 14. At least one nonplanar surface is to be processed
(e.g., junction 16 between airfoil 12 and root 14) to have residual
compressive stresses near the surface in and around junction
16.
[0016] In this example, workpiece 10 is an aluminum alloy fan blade
for a turbofan engine, but the process can be adapted to nearly any
workpiece having a nonplanar surface into which residual
compression stresses are desired to be incorporated.
[0017] Thus in the example of a dovetail-rooted blade, it is
desired to increase residual compressive stresses around both sides
of junction 16 between dovetail root 14 and airfoil 12. As most of
the bending stresses are concentrated around junction 16, this
location is most prone to fatigue damage. The combined effects of
fatigue and corrosion pitting can be reduced via deep rolling
because the residual compressive stress induced by application of
the rolling tool (shown in subsequent figures) reduces the pathways
for damage to propagate through the part, extending the time before
failure or replacement.
[0018] FIG. 2 shows roller disk 20 processing junction 16 of
workpiece/blade 10 between airfoil 12 and root 14. Disk 20 can be
joined to a portion of hub 22 with roller disk 20 rotatable about
an axis 24 angled relative to a downward force direction F. Here,
axis 24 is normal to downward force direction F and thus, resulting
downward contact force is applied to junction 16 generally in
direction F as well.
[0019] Disk 20 has working surface 26 about its perimeter 28, and
can include a profile along its width 30 (best seen in FIGS. 3 and
4), such that an effective radius of the roller disk varies along a
width thereof. It can be seen in FIG. 2 that the disk should be of
a radius that provides clearance over protruding regions of the
workpiece (e.g., dovetail root 14). In a conventional arrangement
for processing a modern aluminum fan blade dovetail, this requires
a minimum disk radius of about 2 inches (51 cm), but the size will
vary depending on a particular application.
[0020] Hub 22 connects disk 20 to a shaft through which the
downward force can be applied in direction F. One example
embodiment of a deep rolling tool incorporating this construction
is shown in FIG. 3. Tool assembly 31 includes spring-loaded shaft
assembly 32 disposed along axis 34, which is parallel to downward
force direction F. Hub 22 can have a first/upper portion 36A along
axis 34 and a second/lower portion 36B at a nonzero angle relative
to axis 34. This angle is therefore consistent with the nonzero
angle between axis 24 and direction F.
[0021] Operation of tool assembly 31 can be as follows. The rolling
operation can include applying a force in direction F along axis 34
such that the applied force is transferred through spring-loaded
shaft assembly 32, hub 22, and roller disk 20 to a first nonplanar
surface of the workpiece (e.g., junction 16). The resulting force
applied to the first nonplanar surface varies along the width of
working surface 26 of the disk due to the variable profile across
width 30 (seen in FIG. 2).
[0022] At least one rolling operation can be performed on a
nonplanar surface using a tool like that shown in FIG. 3. FIG. 3
depicts roller disk 20 joined to second/lower portion 36B of hub
22, and which is rotatable about axis 24 through second/lower
portion 36B of hub 22. Roller disk 20 can be supported on one or
more bearings (best seen in the exploded view of FIG. 4). As noted
with respect to FIG. 2, disk 20 can have working surface 26 about
perimeter 28, and can include a variable or crowned profile. As a
result, an effective radius (and thus applied bearing stresses) of
roller disk 20 varies along working surface 26. Though shown as a
crowned roller with a single center peak, working surface 26 can
additionally have one or more peaks, troughs, etc. The resulting
profile can thus either be curved, slanted, or flat.
[0023] Spring-loaded shaft assembly 32 can take several different
forms. In one non-limiting example, resilient element 46 is
disposed at distal end 48 of shaft assembly 32, while a rigid shaft
50 (best seen in FIG. 4) can be supported on a device to restrain
its movement only along first axis 14. This can include one or more
linear bearings 49. In other embodiments, shaft assembly 32 can
include a flexible beam without a separate resilient element.
[0024] With regard to resilient element 46, certain non-limiting
embodiments include a plurality of stacked Belleville washers 52
which can be selected in number and properties in order to provide
a desired level of resilience. Alternatively, resilient element 30
can include a diaphragm spring or the like.
[0025] Certain embodiments of tool assembly 31 can also optionally
include other elements. For one, tool assembly 31 can include tool
holder 56 mounted to proximal end 58 of rigid shaft 50 and/or shaft
assembly 32. Tool holder 56 can be a standard or custom adapter or
other device to facilitate attachment of tool assembly 31 to
commercially available multi-axis computerized numerical control
(CNC) machines (not shown). Tool holder 56 can additionally or
alternatively facilitate attachment to other devices capable of
steering tool assembly 31 while simultaneously applying sufficient
(but not excessive) force in downward direction F to induce the
desired compressive stresses.
[0026] In certain embodiments, tool assembly 31 can include load
cell 60 to measure the force at the contact surface (see FIG. 4).
Load cell 60 can optionally be disposed along axis 34 adjacent to
resilient element 46, and can include a wired and/or wireless
connection 62 for controller 64. This will be explained in more
detail below.
[0027] FIG. 4 shows an exploded view of tool assembly 31 from FIG.
3. In addition to the elements described generally above, tool
assembly 31 can include the following details. As noted, shaft
assembly 32 is restricted to movement only along first axis 14.
Thus, in this example embodiment, shaft assembly 32 can include
linear bearing 48 arranged along axis 34 for supporting solid shaft
50. This simplifies determination of the downward force that needs
to be applied in direction F, as any deflection away from that axis
causes a reduction in the actual downward force vectors, while also
applying unwanted transverse forces on the tool working
surface.
[0028] In the example shown, hub 22 includes first and second
portions 50A, 50B which form a right, or other, angle therebetween.
Roller disk 20 is supported on a bearing or other device so that it
is rotatable about axis 24. Here, with the right angle, axis 24 is
perpendicular to first axis 14. In this example, working surface 26
of roller disk 20 is symmetrically crowned from a center to
opposing first and second edges. Alternatively, working surface
varies according to a desired load profile along the tool path and
can include peaks, troughs, curves, etc.
[0029] Shaft assembly 32 can be calibrated before or between uses
to provide a desired force concentration at working surface 26 of
roller disk 20. In the example shown, at least one of solid shaft
50 and resilient element 36 can be calibrated so that the force
applied to the tool in direction F (shown in FIGS. 2 and 3) and
transmitted through roller disk 20 is sufficient to impart a
residual compression stress in the workpiece at the first nonplanar
surface (e.g. junction 16 in FIGS. 1 and 2).
[0030] The deep rolling tool described heretofore can be used in a
number of different applications, depending on the required
accuracy and precision of the applied forces needed. Success in
some cases can be achieved by merely controlling the tool load
within previously determined upper and lower bounds, such as
through spring loading the tool and applying a target amount of
compression to the spring. The compliance obtained by using a
spring loaded tool enables an acceptable level of load control
during processing but there is no record of what the actual contact
stress was over the surface. However, this is the cheapest and
often simplest option, where any suitable mechanical device with an
ability to provide a controlled downward force can be used.
[0031] Some parts, however, require that the actual residual
stresses at the working surface be verified. There are currently no
non-destructive evaluation techniques that can be used to verify
the correct level of residual stress was achieved during
processing. Thus, a load cell or another feedback mechanism can be
incorporated into the tool that allows monitoring and/or real-time
adjustment of the force applied through the roller to the
workpiece. The tool can process a part using multiple tool passes
while maintaining the appropriate level of contact stress at the
roller's point of contact. In some cases, the feedback is logged
for quality control, so that it can be determined whether any
irregularities occurred in the process. This is useful where
scrapping and reprocessing parts is not a significant cost or
limiting factor.
[0032] As was shown and described above, load cell 60 can
optionally be incorporated into tool assembly 32. Load cell 60, in
certain embodiments, is contiguous to resilient element 46 (e.g.,
plurality of Belleville washers 52), and enables real time
monitoring of the applied load during processing. A deep rolling
tool with an integral load cell thus enables verification of a key
process parameter, roller load, which is critical for quality
control in many production environments.
[0033] Process consistency could be further enhanced by using the
load cell for closed loop load control which improve the precision
with which the load could be maintained. Such a system would be
much more tolerant of dimensional variability in the components
being processed. It will also ensure that there are no microcracks
on surface due to inadvertent localized application of intensive
pressure.
[0034] Load cell 60 can be in wired or wireless communication with
a controller 64 and/or monitor adapted to receive wired or wireless
signals corresponding to an instantaneous load on resilient element
36. Controller/monitor 64 can include closed-loop feedback logic,
by which it can be adapted to vary a force applied in direction F
(see also FIGS. 2 and 3) on tool assembly 31, along axis 34.
Operating load cell 60 can generate signals corresponding to an
instantaneous load on resilient element 46. The magnitude of the
force can be based at least in part on one or more of the signals
received from and generated by load cell 60. The applied force is
varied based on a plurality of signals from load cell 60 to impart
a substantially equal residual compression stress in the workpiece
along a tool rolling path on the first nonplanar surface.
[0035] The nature of many tools for CNC machines requires that they
be axisymmetric (generally to facilitate rotation of the tool
working end). Thus CNC programming and many common subroutines are
generally tailored to this expectation. In contrast, the
non-axisymmetric nature of tool assembly 31 can require that the
CNC machine be provided with more complex programming even for some
relatively simple tool paths. Depending on the desired tool paths
and number of passes, programming and use of a CNC machine may be
unnecessary or prohibitively complex, in which case, tool assembly
31 can be mounted to a different machine to apply the desired force
over the contact path. While certain processes can generally
performed using a specialized tool in a conventional CNC milling
machine, the deep rolling tool can be inconsistent with generic
subroutines and tool paths used to manipulate conventional
axisymmetric tools. Therefore use of the deep rolling tool, which
is not axisymmetric, has additional path programming constraints.
While planar surfaces can be processed by the deep rolling tool
using a 3-axis CNC machine, more complex geometry components will
require at least a 5-axis machine and in some instances a 6-axis
machine may be necessary. Maintaining the normality and orientation
constraints for deep rolling of complex component geometries can be
challenging as the tool path programming software won't
automatically satisfy these required constraints. While creative
programming can generally overcome these issues it may require an
experienced and highly skilled programmer.
[0036] To overcome this, deep rolling tool assembly 31 can be
attached to the end of a robotic arm 100 as shown in FIG. 5.
Robotic assembly 100 can include, for example, a plurality of
linear arms 102 connected in series between base end 104 and
working end 106. Adjacent ones of arms 102 can be connected via a
corresponding plurality of multi-axis joints 110 such that working
end 106 is articulated by movement of one or more of arms 102
relative to one or more of multi-axis joints 110.
[0037] Operation of a robotic assembly such as assembly 100 in FIG.
5 can include using it to apply a downward force over a rolling
path of non-axisymmetric deep rolling tool assembly 31. The
downward force is applied to a proximal end of a spring-loaded tool
shaft (best seen in FIG. 2) aligned with a first axis, such that
the downward force is transferred through the shaft to a hub
disposed at a distal end of the shaft assembly (also best seen in
FIG. 2). In certain embodiments, robotic assembly 100 is
sufficiently programmed and/or controlled to provide the
appropriate instantaneous feedback of downward force, and the
resilient element in tool 31 can be modified or omitted as
needed.
[0038] As described above, the transferred downward force is
transmitted from an upper portion of the hub aligned with the first
axis to a lower portion of the hub parallel to a second axis. The
second axis forms a nonzero angle relative to the first axis, about
which a roller disk is supported by one or more bearings. A
resulting compressive force is applied to the first nonplanar
surface of the workpiece via a working surface of the roller
disk.
[0039] A typical commercial robot arm has more degrees of freedom
than a 5-axis milling machine which facilitates processing of
complex geometry parts. Current commercially available robot arms
have been developed to the point where they can withstand the
combination of high loads and precision required in deep rolling
applications. The software for controlling robot arms is different
to that for CNC milling machines and is more suited to maintaining
the required orientation constraints of a multi-axis deep rolling
tool. Also, it is easier to accommodate processing of large
components using a robot arm, as the part does not have to fit
inside the machine as it does with a milling machine.
Discussion of Possible Embodiments
[0040] An embodiment of a tool assembly according to an exemplary
embodiment of this disclosure, among other possible things,
includes a robotic assembly including a plurality of linear arms
connected in series between a base end and a working end, adjacent
ones of the plurality of arms connected via a corresponding
plurality of multi-axis joints such that the working end is
articulated by movement of one or more of the plurality of arms
relative to one or more of the plurality of multi-axis joints; a
tool mount connected to an arm or a multi-axis joint at the working
end of the robotic assembly; and a non-axisymmetric deep rolling
tool connected to the tool mount, the non-axisymmetric deep rolling
tool comprising: a spring-loaded shaft assembly disposed along a
first axis; a hub connected to a distal end of the spring-loaded
shaft assembly, the hub having an upper hub portion adjacent to the
distal end of the spring-loaded shaft assembly aligned with the
first axis, and a lower hub portion extending along a second axis,
the second axis forming a nonzero angle relative to the first axis;
and a roller disk joined to the lower portion of the hub, the
roller disk having a working surface about its perimeter and being
rotatable about the second axis parallel to the second portion of
the hub.
[0041] The assembly of the preceding paragraph can optionally
include, additionally and/or alternatively, any one or more of the
following features, configurations and/or additional
components:
[0042] A further embodiment of the foregoing assembly, wherein the
spring-loaded shaft assembly comprises a flexible shaft.
[0043] A further embodiment of any of the foregoing assemblies,
wherein the spring-loaded shaft assembly comprises: a rigid shaft;
and a resilient element disposed at a distal end of the
spring-loaded shaft assembly proximate to the hub.
[0044] A further embodiment of any of the foregoing assemblies,
wherein the rigid shaft is supported by a linear bearing arranged
along the first axis.
[0045] A further embodiment of any of the foregoing
assemblies,wherein the resilient element comprises a plurality of
stacked Belleville washers.
[0046] A further embodiment of any of the foregoing assemblies, and
further comprising: a load cell disposed along the first axis, the
load cell adapted to measure a force applied along the shaft
between a proximal end of the shaft assembly and the roller
disk.
[0047] A further embodiment of any of the foregoing assemblies,
wherein the load cell is contiguous with the resilient element.
[0048] A further embodiment of any of the foregoing assemblies,
wherein the load cell is in communication with a monitor adapted to
receive signals corresponding to an instantaneous load on the
resilient element.
[0049] A further embodiment of any of the foregoing assemblies,
wherein the monitor is part of a controller for the robotic arm
with closed-loop feedback logic, the controller adapted to vary a
downward force applied by the robotic arm to the tool along the
first axis based on one or more of the received signals.
[0050] A further embodiment of any of the foregoing assemblies,
wherein the working surface of the roller disk includes a profile
along its width such that an effective radius of the roller disk
varies along a width thereof.
[0051] An embodiment of a method according to an exemplary
embodiment of this disclosure, among other possible things,
includes supporting a workpiece in a fixture, the workpiece having
a first nonplanar surface: and performing a first rolling operation
on the first nonplanar surface, the first rolling operation
comprising: operating a robotic assembly to apply a downward force
over a rolling path of a non-axisymmetric deep rolling tool, the
downward force is applied to a proximal end of a spring-loaded tool
shaft aligned with a first axis, such that the downward force is
transferred through the shaft to a hub disposed at a distal end of
the shaft assembly; and transmitting the transferred downward force
from an upper portion of the hub aligned with the first axis to a
lower portion of the hub parallel to a second axis, the second axis
forming a nonzero angle relative to the first axis, about which a
roller disk is supported by one or more bearings, such that a
resulting compressive force is applied to the first nonplanar
surface of the workpiece via a working surface of the roller disk;
wherein the robotic assembly comprises a plurality of linear arms
connected in series between a base end and a working end, adjacent
ones of the plurality of arms connected via a corresponding
plurality of multi-axis joints such that the working end is
articulated by movement of one or more of the plurality of arms
relative to one or more of the plurality of multi-axis joints.
[0052] The method of the preceding paragraph can optionally
include, additionally and/or alternatively, any one or more of the
following features, configurations, steps, and/or additional
components:
[0053] A further embodiment of the foregoing method, wherein the
working surface includes a profile along its width such that an
effective radius of the roller disk varies along a width thereof,
such that the resulting compressive force applied to the first
nonplanar surface varies along the width of the working
surface.
[0054] A further embodiment of any of the foregoing methods,
wherein the working surface of the roller disk is crowned from a
center to opposing first and second edges.
[0055] A further embodiment of any of the foregoing methods,
wherein the deep rolling tool shaft comprises: a rigid shaft
extending along the first axis; and a resilient element disposed at
a distal end of the rigid shaft adjacent to the hub.
[0056] A further embodiment of any of the foregoing methods, and
further comprising: operating a load cell disposed along the first
axis to generate signals corresponding to an instantaneous load on
the spring-loaded tool shaft.
[0057] A further embodiment of any of the foregoing methods, and
further comprising: transmitting the signals to a controller for
monitoring the applied compressive forces during the first rolling
operation.
[0058] A further embodiment of any of the foregoing methods, and
further comprising: varying the downward force of the robotic arm
based on the signals generated by the load cell such that the
resulting compressive force is within a predetermined range along a
tool rolling path.
[0059] A further embodiment of any of the foregoing methods, and
further comprising using the tool to perform a second rolling
operation on a second nonplanar surface of the workpiece.
[0060] A further embodiment of any of the foregoing methods,
wherein the workpiece comprises a fan blade for a gas turbine
engine.
[0061] A further embodiment of any of the foregoing methods,
wherein the first nonplanar surface includes a junction between an
airfoil and a dovetail root.
[0062] While the invention has been described with reference to an
exemplary embodiment(s), it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
* * * * *