U.S. patent application number 15/139311 was filed with the patent office on 2016-10-27 for metal 3d printer.
This patent application is currently assigned to SODICK CO., LTD.. The applicant listed for this patent is SODICK CO., LTD.. Invention is credited to Mikio KANEKO.
Application Number | 20160311025 15/139311 |
Document ID | / |
Family ID | 55530483 |
Filed Date | 2016-10-27 |
United States Patent
Application |
20160311025 |
Kind Code |
A1 |
KANEKO; Mikio |
October 27, 2016 |
METAL 3D PRINTER
Abstract
A metal 3-D printer includes a powder layer formation device
having a blade for planarizing metal powder, a table driving device
lowering a table by a predetermined lowering distance in
anticipation of a formation of a powder layer, a laser irradiating
device irradiating a laser beam at the powder layer to form a
sintered layer having a predetermined upper surface region, a
numerical control apparatus controlling the powder layer formation
device, the table driving device, the laser irradiating device and
a machining apparatus. When the blade collides with an obstacle
formed on an upper most sintered layer, an end mill is lowered
according to a predetermined lowering distance such that a lower
end of the end mill is lower than an upper surface of the powder
layer, and moves the end mill across a predetermined upper surface
region of the uppermost sintered layer to remove the obstacle.
Inventors: |
KANEKO; Mikio; (Kanagawa,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SODICK CO., LTD. |
Kanagawa |
|
JP |
|
|
Assignee: |
SODICK CO., LTD.
Kanagawa
JP
|
Family ID: |
55530483 |
Appl. No.: |
15/139311 |
Filed: |
April 26, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02P 10/25 20151101;
B22F 2003/247 20130101; B33Y 40/00 20141201; B33Y 30/00 20141201;
Y02P 10/295 20151101; B22F 2003/1056 20130101; B22F 3/1055
20130101 |
International
Class: |
B22F 3/105 20060101
B22F003/105 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2015 |
JP |
2015-090222 |
Claims
1. A metal 3-D printer, comprising: a table, movable in a vertical
direction; a powder layer formation device, comprising at least one
blade for planarizing metal powder, and moving the at least one
blade in a horizontal axis direction to form a powder layer on the
table; a table driving device, lowering the table by a
predetermined lowering distance in anticipation of a formation of
the powder layer; a laser irradiating device, irradiating a laser
beam at the powder layer to form a sintered layer having a
predetermined upper surface region; a machining apparatus, having a
cutting tool, and moving the cutting tool; and a numerical control
apparatus, controlling the powder layer formation device, the table
driving device, the laser irradiating device and the machining
apparatus, the numerical control apparatus comprising: a memory
which stores the predetermined lowering distance and the
predetermined upper surface region; and a collision detector,
generating a detection signal representing the at least one blade
has collided with an obstacle formed on an upper most sintered
layer, wherein, in response to the detection signal of the
collision detector, the metal 3-D printer lowers the cutting tool
according to the predetermined lowering distance such that a lower
end of the cutting tool is lower than an upper surface of the
powder layer, and moves the cutting tool across the predetermined
upper surface region of the uppermost sintered layer to remove the
obstacle.
2. The metal 3-D printer as claimed in claim 1, wherein the cutting
tool is a rotating end mill.
3. The metal 3-D printer as claimed in claim 1, wherein the powder
layer formation device has a servo motor for moving the at least
one blade, and the collision detector generates the detection
signal when a current supplied to the servo motor increases and
exceeds a set value.
4. The metal 3-D printer as claimed in claim 1, wherein, in
response to the detection signal of the collision detector, the
numerical control apparatus lowers the cutting tool such that the
lower end of the cutting tool is lower than the upper surface of
the powder layer by the predetermined lowering distance.
5. The metal 3-D printer as claimed in claim 1, wherein data
representing a correction distance is stored in the memory, and in
response to the detection signal of the collision detector, the
numerical control apparatus lowers the cutting tool such that the
lower end of the cutting tool is lower than the upper surface of
the powder by a distance which is the correction distance added to
the predetermined lowering distance.
6. The metal 3-D printer as claimed in claim 5, wherein the cutting
tool is a rotating end mill.
7. The metal 3-D printer as claimed in claim 5, wherein the powder
layer formation device has a servo motor for moving the at least
one blade, and the collision detector generates the detection
signal when a current supplied to the servo motor increases and
exceeds a set value.
8. The metal 3-D printer as claimed in claim 5, wherein the
correction distance is a negative value.
9. The metal 3-D printer as claimed in claim 5, wherein, when the
powder layer formation device is forming the powder layer, the
numerical control apparatus moves the cutting tool to a retracted
position such that the lower end of the cutting tool is higher than
the upper surface of the powder layer by a predetermined height,
and in response to the detection signal of the collision detector,
the numerical control apparatus lowers the cutting tool from the
retracted position by a distance which is the predetermined height
and the correction distance added to the predetermined lowering
distance.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Japan
Application No. 2015-090222, filed on Apr. 27, 2015. The entirety
of the above-mentioned patent application is hereby incorporated by
reference herein and made a part of this specification.
BACKGROUND OF THE DISCLOSURE
[0002] 1. Field of the Disclosure
[0003] The disclosure relates to a 3-D printer for additive
manufacturing of a three-dimensional object, and relates
particularly to a 3-D printer having a blade for planarizing metal
powder, and forms a powder layer on a suitable substrate or a
sintered layer.
[0004] 2. Description of Related Art
[0005] Patent Document 1 discloses a 3-D printer which molds a
three-dimensional object by forming multiple layers of material.
This 3-D printer moves a powder dispenser horizontally to form the
powder layer in the molding space. The powder dispenser includes a
hopper which supplies powder material and a drum which planarizes
the powder material. A component which planarizes a powder layer,
such as the drum, is referred to as a blade. The 3-D printer forms
a sintered layer by irradiating a laser beam on a particular region
of the powder layer. A three-dimensional object is molded by
repeatedly forming this type of sintered layer.
[0006] When metal powder is used in a 3-D printer, the blade may
collide with an obstacle on the sintered layer. When the laser beam
is irradiated on the powder layer, sparks including molten metal
may scatter onto the sintered layer. In this way, protrusions which
have hardened to an irregular shape or which have not hardened
sufficiently may be formed on the sintered layer unintentionally.
Typically, a size of the metal powder is 10-50 .mu.m, and a
thickness of a single powder layer is set to 50 .mu.m. In that
case, the blade will collide with protrusions having a height
greater than 50 .mu.m, and molding is temporarily stopped. The
obstacle, generally, is large enough of a protrusion that the blade
may collide.
[0007] Patent Document 2 discloses a 3-D printer for piecewise
removal of obstacles using a cutting tool. When the blade collides
with an obstacle, this 3-D printer makes the blade retreat from the
obstacle and then removes an upper part of the obstacle. After
piecewise removal of the obstacle, formation of the powder layer is
resumed.
[0008] Patent Document 2 also discloses an alternative method of
forming a powder layer to be thicker than the desired sintered
layer, then removing the surplus thickness from the sintered layer
that was formed. In this alternative method, all of the obstacles
are removed piecewise along with the surplus thickness, and a
powder layer is formed on the sintered layer which has had all of
the obstacles removed piecewise.
[0009] Many of the obstacles are minute, namely, protruding by a
height only about a few .mu.m from the powder layer. Therefore, it
is difficult to contact a cutting edge that is formed on a side
surface of a standard cutting tool to only the upper part of the
obstacle. As such, the upper part of the obstacle may remain and
not be completely removed. In that case, when formation of the
powder layer is resumed, the blade may collide with the same
obstacle again. Due to this, molding time may be unnecessarily
long.
[0010] In the alternative method of Patent Document 2, the surplus
thickness is removed each time a sintered layer is formed even if
an obstacle is not formed. As a result, molding time becomes
unnecessarily long. For example, when the height of a sintered
layer is set to 50 nm, a metal 3-D printer is required to perform
the removal of the surplus thickness 2000 times in order to mold a
product with a height of 100 mm.
PRIOR ART LITERATURE
Patent Documents
[0011] Patent Document 1: U.S. Pat. No. 4,863,538
[0012] Patent Document 2: U.S. Pat. No. 7,754,135
SUMMARY OF THE DISCLOSURE
[0013] In view of the forgoing situation, an objective of the
disclosure is to provide a metal 3-D printer which may ensure the
removal of an obstacle and reduce time required for removing the
obstacle. Other objectives and advantages of the disclosure are
described in the description that follows.
[0014] The disclosure relates to a metal 3-D printer including a
table movable in a vertical direction, a powder layer formation
device having at least one blade for planarizing metal powder and
moving the at least one blade in a horizontal axis direction to
form a powder layer on the table, a table driving device lowering
the table by a predetermined lowering distance in anticipation of a
formation of the powder layer, a laser irradiating device
irradiating a laser beam at the powder layer to form a sintered
layer having a predetermined upper surface region, a machining
apparatus having a cutting tool and moving the cutting tool, and a
numerical control apparatus controlling the powder layer formation
device, the table driving device, the laser irradiating device and
the machining apparatus. The numerical control apparatus includes a
memory which stores the predetermined lowering distance and the
predetermined upper surface region, and a collision detector
generating a detection signal representing the at least one blade
has collided with an obstacle formed on an upper most sintered
layer, wherein, in response to the detection signal of the
collision detector, the cutting tool is lowered according to the
predetermined lowering distance such that a lower end of the
cutting tool is lower than an upper surface of the powder layer,
and the cutting tool is moved across the predetermined upper
surface region of the uppermost sintered layer to remove the
obstacle.
[0015] Here, "obstacle" is hardened or insufficiently hardened
metal that has scattered to the sintered layer from an irradiation
position when the laser beam is irradiated on the powder layer. The
"obstacle", generally, is large enough of a metal that the blade
may collide. The phrase "to form a powder layer on the table"
includes forming the powder layer directly or indirectly on the
table. In addition, "to form a powder layer on the table" also
includes forming the powder layer on a suitable substrate placed on
the table or on the sintered layer.
[0016] The cutting tool may be a rotating end mill. The powder
layer formation device has a servo motor for moving the at least
one blade, and the collision detector generates the detection
signal when a current supplied to the servo motor increases and
exceeds a set value.
[0017] In response to the detection signal of the collision
detector, the numerical control apparatus lowers the cutting tool
such that the lower end of the cutting tool is lower than the upper
surface of the powder layer by the predetermined lowering
distance.
[0018] Alternatively, data representing a correction distance is
stored in the memory, and in response to the detection signal of
the collision detector, the numerical control apparatus lowers the
cutting tool such that the lower end of the cutting tool is lower
than the upper surface of the powder by a distance of the
predetermined lowering distance added to the correction
distance.
[0019] Alternatively, when the powder layer formation device is
forming the powder layer, the numerical control apparatus moves the
cutting tool to a retracted position such that the lower end of the
cutting tool is higher than the upper surface of the powder layer
by a predetermined height, and in response to the detection signal
of the collision detector, the numerical control apparatus lowers
the cutting tool from the retracted position by a distance of the
predetermined height and the correction distance added to the
predetermined lowering distance.
[0020] In the disclosure, the obstacle on the sintered layer is
removed only when the blade collides with the obstacle. As such, in
comparison to a case where the upper surface region of the sintered
layer is removed each time the sintered layer is formed, the time
required for removing the obstacle is reduced.
[0021] In addition, the cutting tool is lowered such that the lower
end of the cutting tool is lower than at least the upper surface of
the powder layer, therefore removal of the obstacle is ensured.
Furthermore, the lowering distance of the cutting tool is the
lowering distance of the table, in other words, set to be
equivalent to the thickness of the powder layer. As a result, an
operator is not required to input the lowering distance of the end
mill, therefore problems by an input error of the operator do not
occur. In addition, removal of the obstacle is ensured even if the
thickness of the powder layers change.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a side view diagram illustrating a metal 3-D
printer according to an embodiment of the disclosure.
[0023] FIG. 2 is a perspective view illustrating a metal 3-D
printer of FIG. 1.
[0024] FIG. 3 is a perspective view of a recoating head of FIG. 2
viewed from the top side.
[0025] FIG. 4 is a perspective view of a recoating head of FIG. 2
viewed from the bottom side.
[0026] FIG. 5 is a block diagram illustrating an example of a CAM
system and a numerical control apparatus.
[0027] FIG. 6 is a side view diagram illustrating a tool in a
retreat position and a blade colliding with an obstacle.
[0028] FIG. 7 is a side view diagram illustrating a tool in a
lowered position and a blade which has returned to a retreat
position.
[0029] FIG. 8 is a side view diagram illustrating a tool which has
returned to a retreat position.
[0030] FIG. 9 is a side view diagram illustrating a tool in a
lowered position and a blade which has returned to a retreat
position.
DESCRIPTION OF THE EMBODIMENTS
[0031] Embodiments of the disclosure accompanied with figures are
described in detail. As shown in FIG. 1, a metal 3-D printer 1 has
a molding room 1A and a driving device room 1B. The molding room 1A
is disposed at a front side of the metal 3-D printer 1, and the
driving device room 1B is disposed behind the molding room 1A. The
molding room 1A and the driving device room 1B are separated by a
bellows 1C.
[0032] It is known that when metal powder is sintered by a laser
beam, a special smoke referred to as fume is generated. If the fume
in the molding room 1A shields the laser beam, a required energy of
the laser beam may not reach the powder layer. During molding, an
inert gas supply device (not illustrated) supplies clean inert gas
to the molding room 1A and the driving device room 1B respectively,
such that the fume does not shield the laser beam. A molding space,
for forming multiple layers of metal material, is provided in the
molding room 1A. A table 2 is housed in the molding room 1A. The
molding space is formed at an entire region of an upper side of the
table 2. The table 2 moves down by a height corresponding to the
thickness of the powder layer in anticipation for a formation of
the powder layer.
[0033] As shown in FIG. 2, the metal 3-D printer 1 includes a
slider 24, a transmission device 26 and a table driving device. The
slider 24 supports the table 2, and is configured to be movable in
a vertical U axis direction. The transmission device 26 includes a
coupling, a ball screw and a nut, wherein the nut is attached to
the slider 24. The table driving device includes a motor 28,
wherein rotation of the motor 28 is converted to a vertical
movement of the slider 24 by the transmission device 26.
[0034] As shown in FIG. 2, a powder layer formation device 3, which
forms a powder layer of a predetermined thickness on the table 2,
includes a recoating head 30 and a pair of guide rails 32R, 32L.
The recoating head 30 supplies the metal powder onto the table 2, a
suitable substrate or the sintered layer by moving in a horizontal
S axis direction.
[0035] As shown in FIGS. 3 and 4, the recoating head 30 includes a
material container 35, blades 34, 36, and a pair of bearings 31R,
31L. The material container 35 collects metal powder, and a
discharge port 37 is formed at a bottom of the material container
35. The discharge port 37 extends in a horizontal direction that is
orthogonal to the S axis, and is opened and closed by a suitable
shutter. When the recoating head 30 is at a retracted position, the
discharge port 37 is closed. When the recoating head 30 is moving
forward to form a powder layer, the discharge port 37 is open and
metal powder drops down.
[0036] The blades 34, 36 planarize the metal powder dropped down
from the discharge port 37. The blades 34, 36 extend in a
horizontal direction that is orthogonal to the S axis, and are
disposed next to the discharge port 37. The blade 34 is disposed in
front of the discharge port 37, and the blade 36 is disposed behind
the discharge port 37. The pair of guide rails 32R, 32L extend
parallel with the S axis. The bearings 31R, 31L are engaged with
the guide rails 32R, 32L respectively, and the guide rails 32R, 32L
guide the recoating head 30 in the S axis direction. A suction pipe
for sucking the fume is disposed at the guide rail 32R. A supply
pipe for supplying inert gas is disposed at the guide rail 32L.
[0037] Suction ports 38, 39 for sucking fume are formed at a front
surface and a rear surface respectively of the recoating head 30.
The fume sucked by the suction ports 38, 39 is discharged out of
the molding room 1A. A fixed material supply device (not
illustrated) which supplies metal powder to the material container
35 is provided. Metal powder is replenished to the material
container 35 from the material supply device at suitable times,
such that there is no shortage of metal powder in the material
container 35 during the molding period.
[0038] The powder layer formation device 3 includes a servo motor 4
which moves the recoating head 30 to reciprocate horizontally in
the S axis direction along the pair of guide rails 32R, 32L. A
rotation axis of the servo motor 4 is connected to the recoating
head 30 by a suitable transfer mechanism. The transfer mechanism,
for example, is constructed by a ball screw and a nut.
[0039] A laser irradiating device 5 irradiates a laser beam on a
predetermined region of the powder layer. The laser irradiating
device 5, as shown in FIG. 2, includes a laser scanning apparatus
5A, a laser oscillator 5B, a focus lens 5C and a plurality of laser
transfer components (not illustrated). The laser scanning apparatus
5A is disposed on a ceiling of the molding room 1A, and includes a
pair of galvanometer mirrors 56, 58. The upper galvanometer mirror
56 is supported to rotate or oscillate around a horizontal A axis.
The lower galvanometer mirror 58 is supported to rotate or
oscillate around a horizontal B axis. The B axis is orthogonal to
the A axis.
[0040] The laser beam with a predetermined energy which is
outputted from the laser oscillator 5B arrives at the galvanometer
mirrors 56, 58 through the laser transfer components. The laser
beam reflected by the pair of galvanometer mirrors 56, 58 is
converged using the focus lens 5C and passes through a transmission
lens 1D. As shown in FIG. 1, the transmission lens 1D is disposed
on a hole formed on the ceiling of the molding room 1A. The laser
beam converged by the focus lens 5C is irradiated on the powder
layer by a spot diameter that is predetermined.
[0041] As shown in FIG. 1, a machining apparatus 8 includes a Y
moving body 86 and an X moving body 84. The Y moving body 86 is
driven by a Y linear motor 42, and is movable in a horizontal Y
axis direction. The X moving body 84 is driven by an X linear motor
52, and is movable in a horizontal X axis direction that is
orthogonal to the Y axis. The Y moving body 86 and a majority of
the X moving body 84 are disposed in the driving device room
1B.
[0042] A machining head 82 is attached to a front surface of the X
moving body 84. The machining head 82 is movable in a vertical Z
axis direction through a Z linear motor 62. A suitable spindle is
rotatably disposed in the machining head 82. An end mill 9, which
is a cutting tool, is attached vertically to the spindle. A cutting
edge for performing machining is formed on a side surface of the
end mill 9.
[0043] The X linear motor 52, the Y linear motor 42 and the Z
linear motor 62 are controlled by a numerical control apparatus 10.
In this way, the numerical control apparatus 10 moves the end mill
9 in the X axis, the Y axis and the Z axis direction, such that a
position of a lower end 9A of the end mill 9 may be controlled to
any height in the molding room 1A. The sintered layer may be
machined by the cutting edge of the rotating end mill 9.
[0044] As shown in FIG. 5, the metal 3-D printer 1 includes a CAM
system 18, the numerical control apparatus 10, a laser controller
20, a servo motor controller 70, a Y linear motor controller 40, an
X linear motor controller 50 and a Z linear motor controller 60.
The CAM system 18 constructs a molding program for molding a
3-dimensional object. The molding includes: formation of a powder
layer; formation of a sintered layer; and machining by an end
mill.
[0045] The numerical control apparatus 10 is constructed by a
memory device 11 and an arithmetic device 12. The memory device 11,
for example, is a hard disk which stores the molding program. In
anticipation for a formation of a powder layer, data representing a
lowering distance d for lowering the table 2 is included in the
molding program. The arithmetic device 12 includes a decoder 14, a
memory 13, a command generator 15, a distributor 16 and a collision
detector 17. The decoder 14 decodes the molding program that is
stored in the memory device 11. The memory 13 is memory for
temporarily storing the decoded molding program. The command
generator 15 generates a command according to the decoded molding
program. The distributor 16 distributes the command from the
command generator 15 to various controllers.
[0046] The numerical control apparatus 10 generates a command
position which sets a height of the table 2, and controls the table
driving device. The table driving device moves the table 2 in the U
axis direction according to the command position. The numerical
control apparatus 10 generates a move command which sets the
forward movement or the backward movement of the recoating head 30,
and controls the servo motor 4 of the powder layer formation device
3 in cooperation with the servo motor controller 70. The servo
motor 4 moves the recoating head 30 in the S axis direction. The
servo motor controller 70 for controlling the servo motor 4 is
disposed between the numerical control apparatus 10 and the servo
motor 4.
[0047] The distributor 16 of the numerical control apparatus 10
provides the move command to the servo motor controller 70. An
angular position of the servo motor 4 is detected, and the detected
position is fed-back to the servo motor controller 70. When the
move command is inputted to the servo motor controller 70, a
command current is supplied to a driver 71. The driver 71 supplies
a driving current to the servo motor 4 according to the command
current. In this way, the recoating head 30 moves in the S axis
direction at a predetermined speed.
[0048] A current probe for detecting the current supplied to the
servo motor 4 is disposed between the driver 71 and the servo motor
4. The detected current is fed-back to the driver 71 from the
current probe, and the driver 71 corrects the driving current. A
signal representing the detected current is provided to the
collision detector 17 through the driver 71 and the servo motor
controller 70.
[0049] The numerical control apparatus 10 generates a scan position
command which sets a location on the powder layer to irradiate the
laser beam, a scan speed command which sets a speed to move the
laser beam on the irradiation position, and controls the laser
irradiating device 5 in cooperation with the laser controller 20. A
pair of electric actuators 23 are disposed to rotate or oscillate a
mirror surface of the galvanometer mirrors 56, 58 respectively. One
of the electric actuators 23 is rotates or oscillates the
galvanometer mirror 56 around the A axis, and the other electric
actuator 23 rotates or oscillates the galvanometer mirror 58 around
the B axis.
[0050] The distributor 16 of the numerical control apparatus 10
provides the scan position command and the scan speed command to
the laser controller 20. The laser controller 20 provides the
command position and command velocities of the A axis and the B
axis to an electric actuator controller 21 according to the scan
position command and the scan speed command. In addition, a
position of the A axis and the B axis of the pair of electric
actuators 23 are detected, and the detected positions are fed-back
to the electric actuator controller 21.
[0051] The laser controller 20 supplies the command current to a
driver 22 according to the command position, the command velocity
and the detected position. In this way, the irradiation position of
the laser beam moves on the powder layer at the scan speed command.
A current probe for detecting a current supplied to the pair of
electric actuators is disposed between the driver 22 and the pair
of electric actuators 23. The detected current is fed-back to the
driver 22 from the current probe, and the driver 22 corrects the
driving current.
[0052] The numerical control apparatus 10 generates a command which
sets a position and a speed of the end mill 9, and controls the
machining apparatus 8 in cooperation with the Y linear motor
controller 40, the X linear motor controller 50 and the Z linear
motor controller 60. The Y linear motor 42 moves the Y moving body
86 in the Y axis direction. The Y linear motor controller 40 for
controlling the Y linear motor 42 is disposed between the numerical
control apparatus 10 and the Y linear motor 42.
[0053] The distributor 16 of the numerical control apparatus 10
provides the command position and the command velocity to the Y
linear motor controller 40. In addition, a position of the Y linear
motor 42 is detected, and the detected position is fed-back to the
Y linear motor controller 40. The Y linear motor controller 40
supplies a command current to a driver 41 according to the command
position, the command velocity and the detected position. The
driver 41 supplies a driving current to the Y linear motor 42
corresponding to the command current. In this way, the Y moving
body 86 moves in the Y axis direction at the command velocity. A
current probe for detecting a current supplied to the Y linear
motor 42 is disposed between the driver 41 and the Y linear motor
42. The detected current is fed-back to the driver 41 from the
current probe, and the driver 41 corrects the driving current.
[0054] The X linear motor 52 moves the X moving body 84 in the X
axis direction. The X linear motor controller 50 for controlling
the X linear motor 52 is disposed between the numerical control
apparatus 10 and the X linear motor 52. The distributor 16 of the
numerical control apparatus 10 provides the command position and
the command velocity to the X linear motor controller 50. In
addition, a position of the X linear motor 52 is detected, and the
detected position is fed-back to the X linear motor controller 50.
The X linear motor controller 50 supplies a command current to a
driver 51 according to the command position, the command velocity
and the detected position. In this way, the X moving body 84 moves
in the X axis direction at the command velocity. A current probe
for detecting a current supplied to the X linear motor 52 is
disposed between the driver 51 and the X linear motor 52. The
detected current is fed-back to the driver 51 from the current
probe, and the driver 51 corrects the driving current.
[0055] The Z linear motor 62 moves the machining head 82 in the Z
axis direction. The Z linear motor controller 60 for controlling
the Z linear motor 62 is disposed between the numerical control
apparatus 10 and the Z linear motor 62. The distributor 16 of the
numerical control apparatus 10 provides the command position and
the command speed to the Z linear motor controller 60. In addition,
a position of the Z linear motor 62 is detected, and the detected
position is fed-back to the Z linear motor controller 60. The Z
linear motor controller 60 supplies a command current to a driver
61 according to the command position, the command velocity and the
detected position. In this way, the machining head 82 moves in the
Z axis direction at the command velocity. A current probe for
detecting a current supplied to the Z linear motor 62 is disposed
between the driver 61 and the Z linear motor 62. The detected
current is fed-back to the driver 61 from the current probe, and
the driver 61 corrects the driving current.
[0056] A process of the metal 3-D printer 1 molding a 3-dimensional
object by forming multiple layers of metal material is described in
detail with reference to FIG. 5. First, the molding program of a
3-dimensional object is constructed by the CAM system 18 according
to a model of the 3-dimensional object. The molding program
includes molding conditions, and are stored in the memory device 11
of the numerical control apparatus 10. The molding program in the
memory device 11 is taken in by the arithmetic device 12 of the
numerical control apparatus 10. The molding program is stored in
the memory 13 and is decoded by the decoder 14. The decoder 14
provides the decoded molding program to the command generator 15.
The command generator 15 generates various commands in the decoding
order of the molding program. The commands are provided to a
suitable controller by the distributor 16.
[0057] In response to a move command, the servo motor controller 70
controls the servo motor 4 such that the recoating head 30 moves in
the horizontal S axis direction in the molding space. Along with
the forward movement of the recoating head 30, metal powder in the
material container 35 drops down from the discharge port 37. The
metal powder is planarized by the blades 34, 36. In this way, a
first powder layer is formed on the table 2 or an appropriate base
plate. The laser beam is irradiated on a predetermined region of
the first powder layer, and a first sintered layer is formed. After
the first sintered layer is formed, the table 2 and the slider 24
are lowered in the vertical U axis direction by the lowering
distance d. The lowering distance d is equivalent to a thickness of
the next powder layer.
[0058] A second powder layer is formed on the first sintered layer.
The laser beam is irradiated on a predetermined region of the
second powder layer, and a second sintered layer is formed. In this
way, the formation of a sintered layer is repeated, and the desired
3-dimensional object is molded. The lowering distance d of the
table 2, in other words the thickness of the powder layer, may be
constant or may vary. The machining apparatus 8 finishes a side
surface of the sintered layer when each or a plurality of sintered
layers are formed.
[0059] When the blade 34 of the metal 3-D printer 1 collides with
an obstacle, the obstacle is removed by the machining apparatus 8.
As a result, the 3-dimensional object is molded without being
stopped. A movement of the metal 3-D printer 1 when the blade 34
collides with an obstacle is described in detail with reference to
FIGS. 5, 6, 7 and 8. In FIGS. 6, 7 and 8, six sintered layers are
formed. Reference numeral 7 represents the powder layer formed on
top of the upper most sintered layer 6.
[0060] As shown in FIG. 6, protrusions of varying sizes are formed
on the sixth sintered layer 6. In FIG. 6, the blade 34 which is
moved horizontally from a retracted position at the right side to
the left is in collision with an obstacle 6A. During the formation
of the powder layer, the end mill 9 is stopped at the retracted
position at the left side, and the lower end 9A of the end mill 9
is at the same height of an upper surface 7a of the powder layer 7.
In a case when the blade 34 collides with the obstacle 6A, the
detected current of the current probe rises. As shown in FIG. 5,
the collision detector 17 constantly monitors the detected current.
The collision detector 17 compares the detected current with a set
value. When the detected current exceeds the set value, the
collision detector 17 detects that the blade 34 has collided with
the obstacle 6A. A detection signal representing the collision is
provided to the command generator 15.
[0061] The command generator 15 generates a cut-off command in
response to the detection signal of the collision detector 17. The
cut-off command is provided to the servo motor controller 70
through the distributor 16. As a result, the command current of the
servo motor controller 70 is cut off, and the current supplied from
the driver 71 to the servo motor 4 is stopped. In this way, the
servo motor 4 is stopped, and the blade 34 elastically rebounds
with respect to the obstacle 6A and runs to the right horizontally
in FIG. 6.
[0062] After a predetermined time, the command generator 15
provides a move command to the servo motor controller 70 in an
opposite direction. The driver 71 resumes supplying current to the
servo motor 4, and the blade 34 moves to the right in FIG. 6 and
returns to the retracted position. FIG. 7 illustrates the blade 34
returned to the retracted position. The command generator 15
obtains data representing the lowering distance d from the molding
program stored in the memory 13. The command generator 15 provides
a command position for removing the obstacle 6A to the Y linear
motor controller 40, the X linear motor controller 50 and the Z
linear motor controller 60 through the distributor 16.
[0063] As shown in FIG. 7, the machining apparatus 8 lowers the end
mill 9 by a distance corresponding to the lowering distance d in
response to a command from the command generator 15. In the present
embodiment, the lowering distance of the end-mill 9 is the lowering
distance d of the table 2, in other words, equivalent to a
thickness of the powder layer 7. As a result, the lower end 9A of
the end mill 9 is at a lower surface 7b of the powder layer 7, in
other words, equivalent to a height of an upper surface 6a of the
sintered layer 6. The rotating end mill 9 of the machining
apparatus 8 is moved horizontally across the upper surface 6a of
the sintered layer 6, and the blade of the end mill 9 is contacted
to the base of the protrusions. In this way, as shown in FIG. 8,
all of the protrusions on the sintered layer 6, including the
obstacle 6A, are removed by the blade of the end mill 9. Then,
formation of the powder layer 7 is resumed.
[0064] In the present embodiment, the end mill 9 does not level the
sintered layer for each of the sintered layers that are formed. The
end mill 9 removes the obstacle 6A only when the blade 34 collides
with the obstacle 6A. In this way, the time required for molding
may be shortened since the time required for removing the obstacle
6A is reduced.
[0065] In addition, the lowering distance d for lowering the table
2, in anticipation of the formation of a powder layer, is used as
the lowering distance of the end mill 9. In this way, an operator
is not required to input the lowering distance of the end mill 9 to
the numerical control apparatus 10 in anticipation of the removal
of the obstacle 6A. Removal of the obstacle 6A is ensured by
lowering the lower end 9A of the end mill 9 to the height of the
lower surface 7B of the powder layer 7, and moving the lower end 9A
of the end mill 9 along the upper surface 6a of the sintered layer
6.
[0066] In addition, the lowering distance of the end mill 9 is
dependent on the lowering distance d of the table 2. As such, the
lowering distance of the end mill 9 is a value adapted for removing
the obstacle 6A even if thicknesses of the powder layers that are
formed are different.
[0067] The embodiment was chosen in order to explain the principles
of the disclosure and its practical application. Many modifications
and variations are possible in light of the above teachings. It is
intended that the scope of the disclosure be defined by the
claims.
[0068] In the present embodiment, the lowering distance of the end
mill 9 is equivalent to the lowering distance d of the table 2.
Alternatively, the lowering distance of the end mill 9 may be a
value of the lowering distance d of the table 2 corrected by a
predetermined correction distance .DELTA.d. In this case, the
operator sets the correction distance .DELTA.d before molding, and
the molding program includes data representing the predetermined
correction distance .DELTA.d. When the collision detector 17
detects a collision of the blade 34 and the obstacle 6A, the
command generator 15 obtains data representing the lowering
distance d and the correction distance .DELTA.d from the molding
program stored in the memory 13. The command generator 15 provides
the command position for lowering the end mill 9 to the Z linear
motor controller 60 through the distributor 16 according to the
lowering distance d and the correction distance .DELTA.d.
[0069] As shown in FIG. 9, the numerical control apparatus 10
lowers the end mill 9 by a distance which is the correction
distance .DELTA.d added to the lowering distance d. Since the
thickness of the sintered layer shrinks compared to the original
powder layer, the correction distance .DELTA.d may be set according
to a difference in the thicknesses of the powder layer and the
sintered layer. The correction distance .DELTA.d may be set
according to a material of the metal powder. In order to save time
required for removing the obstacle 6A, the correction distance
.DELTA.d may be a negative value. In that case, the numerical
control apparatus 10 controls the machining apparatus 8 to lower
the end mill 9 according to a predetermined lowering distance d
such that the lower end 9A of the end mill 9 is lower than the
upper surface 7a of the powder layer 7.
[0070] In the present embodiment, when the end mill 9 is at the
retracted position, the lower end 9A of the end mill 9 is at a same
height as the upper surface 7a of the powder layer 7. However, a
retracted position of the end mill 9 is not limited thereto.
Alternatively, when the powder layer formation device 3 is forming
the powder layer 7, the numerical control apparatus 10 may move the
end mill to a retracted position represented by the dash-dot-dash
line in FIG. 9. When the end mill 9 is at this retracted position,
the lower end 9A of the end mill 9 is higher than the upper surface
7a of the powder layer 7 by a predetermined height h. Data
representing the predetermined height h may be stored in the memory
13. In this case, in order to remove the obstacle 6A, the numerical
control apparatus 10 lowers the end mill 9 by a distance which is
the predetermined height h and the correction distance .DELTA.d
added to the lowering distance d of the table 2.
[0071] In the present embodiment, when the blade 34 collides with
the obstacle 6A, the metal 3-D printer 1 stops the servo motor 4,
and the blade 34 runs to the right in FIG. 6. Alternatively, the
blade 34 may be retracted from the obstacle 6A by rotating the
servo motor 4 in reverse. In the present embodiment, the recoating
head 30 includes two blades 34, 36, however, only one blade may be
included as well.
* * * * *