US20040102136A1

US20040102136A1 - Spring-loaded contour following end effectors for lapping/polishing

Info

Publication number: US20040102136A1
Application number: US10/302,042
Authority: US
Inventors: Jeffrey Wood; Robert Bender
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 2002-11-21
Filing date: 2002-11-21
Publication date: 2004-05-27
Also published as: WO2004048037A3; AU2003291154A1; AU2003291154A8; WO2004048037A2

Abstract

End effectors are provided for performing surface lapping using a robot. The end effectors allow orthogonal surface contact in order to maintain optimum pressure applied by the robot. One or more end effectors include a base, a plate, a lapping pad attached to the plate, and a pivot joint. The pivot joint allows the plate to pivot about two substantially orthogonal axes. The base is attached to an arm of a robot. The end effector includes a component for absorbing applied pressure, such as a spring-loaded shaft or a pneumatic shaft. In an aspect of the invention, the two axes are substantially parallel to the planar surface.

Description

RELATED APPLICATION

This patent application is related to concurrently-filed patent applications entitled “Contour Following End Effectors for Lapping/Polishing”, bearing attorney docket number BOEI-1-1101, and “Automated Lapping System”, bearing attorney docket number BOEI-1-1121, which are hereby incorporated by reference.[0001]

GOVERNMENT LICENSE RIGHTS

[0002] This invention was made with Government support under U.S. Government contract F33615-97-2-3400 awarded by United States Air Force. The Government has certain rights in this invention.

FIELD OF THE INVENTION

This invention relates generally to lapping and polishing surfaces and, more specifically, to robotic lapping and polishing.

BACKGROUND OF THE INVENTION

Injection-molded aircraft canopies and windshields offer tremendous benefits to aircraft in cost, weight, and impact tolerance. A major cost in this manufacturing process is the injection mold itself. Surfaces of canopies and windshields are finished to a quality similar to an optic lens in order to prevent pilots from being subjected to visual distortion. The precise optics for canopies and windshields are built into the injection mold. The injection molds are lapped or polished by hand, section by section, using a diamond plated lapping material. Hand polishing or lapping an injection mold takes several man-years to accomplish. Thus, lapping or polishing is very costly. Hand polishing or lapping also does not ensure that the precise, optic surface finish quality has been met.

Therefore, there exists an unmet need to reduce the cost and increase the accuracy of lapping or polishing.

SUMMARY OF THE INVENTION

The present invention provides end effectors for performing surface lapping using a robot. The end effectors allow orthogonal surface contact in order to maintain optimum pressure applied by the robot.

The present invention includes one or more end effectors with a base, a plate, a lapping pad attached to the plate, and a pivot joint. The pivot joint allows the plate to pivot about two substantially orthogonal axes. The base is attached to the robotic arm. The end effector includes a component for absorbing applied pressure.

In an aspect of the invention, the component includes a spring-loaded shaft or a pneumatic shaft.

In another aspect of the invention, the two axes are substantially parallel to the planar surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings. [0010]
FIG. 1 is a perspective view of an end effector in operation with a robot; [0011]
FIG. 2 is an exploded view of exemplary materials layered on an end effector; [0012]
FIGS. 3A and B illustrate a spring-loaded, universal joint end effector; [0013]
FIGS. 4A and B illustrate a spring-loaded, hexagonal joint end effector; [0014]
FIGS. 5A and B illustrate a gimbaled joint end effector with a spring-loaded shaft; [0015]
FIGS. 6A and 6B illustrate a half ball and socket joint end effector with a spring-loaded shaft; [0016]
FIGS. 7A and 7B illustrate a pneumatic end effector; and [0017]
FIGS. [0018] 8A-C illustrate a multi-end effector support.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an embodiment of an [0019] end effector 40 according to the present invention that is attached to a robot 42 for polishing and lapping a work product 44. A non-limiting example of the product 44 is a core or cavity injection mold for making polycarbonate aircraft canopies. The work product 44 suitably entails a high degree of polishing or lapping accuracy. For example, precise optical properties for injection molds must be attained in order to produce optically flawless or near-flawless polycarbonate molded canopies. In order to attain this desired level of accuracy, the end effector 40 pivots at an end of the robot 42, but does not rotate about an axis that is perpendicular to a planar surface of the end effector 40. In other words, the end effector 40 maintains a substantially orthogonal position relative to the work product 44.
The spring-loaded [0020] end effectors 40 are suitable for use with a robot that is configured with rigid motion and fixed positioning as compared to robots configured with soft float functions, such as Fanuc robots. A non-limiting example of the robot 42 is a Cooper robot. Without soft float, shut-offs may occur if the robot 42 applies too much pressure to a surface. The spring-loaded end effectors 40 allow the robot 42 to apply continuous, consistent pressure without incurring unnecessary shut-offs. The present invention far exceeds the capabilities of a human operator, therefore lapping and polishing evolutions take a fraction of the time taken by a human operator. The spring-loaded end effectors 40 include springs or pressure applying/absorbing devices for absorbing a predefined amount of pressure in order to apply pressure-loaded diamond laps on the work surface for accelerated material removal, and to avoid unnecessary robot shutdowns due to over travel.
As shown in FIG. 2, the [0021] end effector 40 suitably includes a lapping plate 50 with applied layers of materials that aid in lapping the work product 44. In one embodiment, the layers of materials include one or more silicon adhesive layers 54 interleaved with one or more solid acrylic rings 56. A pitch substance 60, such as tree pitch produced by Universal Photonics, Inc., Adolf Miller, or Zophar Mills, Inc., is applied to the last acrylic ring 56. A polishing or abrasive material 62, such as a diamond-plated lapping material, is attached to the pitch 60. The robot 42 applies pressure to the work product 44 through the end effector 40 in order to for the pitch 60 to conform to the surface of the work product 44. The robot 42 moves the end effector 40 over a section of the surface of the work product 44 that entails the same curvature to which the pitch 60 conforms.

Spring-Loaded Joints

FIGS. 3A and B illustrate a non-limiting [0022] example end effector 100 that suitably attaches to the robot 42 (FIG. 1). The end effector 100 includes a universal joint 104 that couples a base mount 106 to a lapping plate 110. The base mount 106 suitably attaches to the robot 42 (FIG. 1). The universal joint 104 suitably includes a U-shaped receiver portion 114, a pin housing 116, and a U-shaped lapping plate portion 120. The U-shaped receiver portion 114 is part of or is securely attached to the base mount 106. The U-shaped lapping plate portion 120 is suitably part of or is alternatively securely attached to, the lapping plate 110.
A [0023] first pin 124 is mounted through the U-shaped receiver portion 114 and the pin housing 116. The pin housing 116 rotates about a longitudinal axis of the first pin 124. Second and third pins 130 and 132 are mounted through the U-shaped lapping plate portion 120 and into the pin housing 116 to allow the U-shaped lapping plate portion 120 to rotate about a longitudinal axis of the second and third pins 130 and 132. The second and third pins 130 and 132 are substantially axially orthogonal to the first pin 124. Thus, the universal joint 104 allows the lapping plate 110 to rotate about the axis of the first pin 124 and the axis of the second and third pins 130 and 132 without allowing rotation of the lapping plate 110 itself.
A [0024] compression spring 140 encircles the universal joint 104, thereby putting expanding pressure on the base mount 106 and the lapping plate 110. When pressure is applied to the lapping plate 110, the U-shaped lapping plate portion 120 slides the second and third pins 130 and 132 through the compression slots 144 while compressing the compression spring 140.
FIGS. 4A and B illustrate a spring loaded, hexagonal ball and socket [0025] joint end effector 200. The end effector 200 includes a base 204, a hexagonal ball 202, and a lapping plate 206 with a hexagonal bushing 210. FIG. 4B is a cutaway view of the end effector 200. The hexagonal ball 202 includes a first cavity 212 along the centerline of a shaft of the hexagonal ball 202 and a second cavity 214 within a portion of the base 204. A single flexible retaining wire 216 is attached at opposing sides of the second cavity 214 by first and second clamp screws 218 and 220. The flexible retaining wire 216 travels from the first clamp screw 218 through the first cavity 212 and out of the hexagonal ball 202 around a securing pin 222 back into the hexagonal ball 202 to the second clamp screw 220. The securing pin 222 is securely attached within the hexagonal bushing 210. A compression spring 208 is wrapped around the shaft of the hexagonal ball 202 and applies an expanding force to the base 204 and the hexagonal bushing 210.
When pressure is applied to the [0026] lapping plate 206, the spring 208 compresses and the flexible retaining wire 216 flexes within the second cavity 214. The flexible retaining wire 216 keeps the hexagonal ball 202 within the hexagonal bushing 210.

Spring-Loaded Shafts

FIGS. 5A and B illustrate a gimbaled-[0027] joint end effector 150 with a spring-loaded shaft. The gimbaled-joint end effector 150 includes a gimbaled-joint section 156 coupled to a spring-loaded shaft section 158. The spring-loaded shaft section 158 includes a first base 162, a second base 164, first and second shaft bushings 170 and 172, a spline shaft 176, and a spring 178. The second base 164 is securely attached to a base of the gimbaled-joint section 156. The second base 164 includes a cavity for receiving the second shaft bushing 172. The second shaft bushing 172 includes a cavity with a toothed wall configured to receive the spline shaft 176. The spline shaft 176 and the second shaft bushing 172 are suitably secured within the second base 164 by a pin 180 that passes through opposing sidewalls of the second base 164, the second shaft bushing 172, and the spline shaft 176. The first shaft bushing 170 is positioned within a cavity of the first base 162. The first shaft bushing 170 includes a cavity with toothed walls for receiving the spline shaft 176. The first shaft bushing 170 includes a vertical notch 186 for receiving a pin 182 that is securely attached to the spline shaft 176. The vertical notch 186 allows for motion of the spline shaft 176 vertically within the first shaft bushing 170.
A [0028] spring 178 is positioned around the spline shaft 176 between the first and second shaft bushings 170 and 172. The spring 178 maintains an expanding force on the first shaft bushing 170 and the second shaft bushing 172. Thus, when pressure is applied to the gimbaled-joint section 156, the second shaft bushing 172 moves the spline shaft 176 with the attached pin 182 up the vertical notch 186 and compresses the spring 178.
FIGS. 6A and B illustrate a one-half ball [0029] socket end effector 240 with spring-loaded shaft. The one-half ball and socket end effector 240 includes a socket housing 244, a half-ball lapping plate 246, and first and second pins 248 and 250. The lapping plate 246 includes a one-half ball joint portion 256 that is pivotally received by a semi-circular cavity 252 formed by the socket housing 244. The pins 248 and 250 pass through opposite sides of the socket housing 244 and protrude into the cavity 252. The distance between the pins 248 and 250 is less than a diameter of a widest part of the one-half ball joint portion 256. Thus, the one-half ball joint portion 256 swivels within the socket housing 244 and is maintained within the cavity 252 by the pins 248 and 250.
The [0030] socket housing 244 is coupled to a shaft 260 that is suitably coupled to a robot arm. The shaft 260 receives a spring support washer 262 and a compression spring 264. A securing pin 266 allows the shaft 260 to be slidably received by a support structure (not shown). When pressure is applied to the half-ball lapping plate 246, the shaft 260 slides through the support structure and compresses the spring 264 between the spring support washer 262 and the support structure. Therefore, the one-half ball socket end effector 240 absorbs some applied pressure in order to avoid any unnecessary robot shut-offs.

Pneumatic Shock

FIGS. [0031] 7A-C illustrate a one-half ball socket end effector 300 with a pneumatic shock. The end effector 300 includes a pneumatic shock section 304 that connects to a end effector portion 306. The pneumatic shock section 304 includes a pneumatic housing 310, a shock 312, a housing cap 314, and a connector 316 coupled to a pneumatic input line 320. The pneumatic input line 320 receives pressurized air from a pneumatic source pump (not shown) that is controlled by a controlling device (not shown). The shock 312 includes a shaft 324 that passes through an opening at a first end of the pneumatic housing 310. The shock 312 also includes a plunger portion 326 attached to the shaft 324. The plunger portion 326 is larger in diameter than the shaft 324 and larger than an opening at a first end of the pneumatic housing 310. The plunger portion 326 is surrounded by a seal 328 that mates with an interior wall of the pneumatic housing 310 for avoiding air leakage pass the plunger portion 326. A second end of the pneumatic housing 310 that is opposite the first end is capped by the housing cap 314 that includes a receiving cavity for securely connecting to the connector 316. The connector 316 securely receives the pneumatic input line 320 from the pneumatic source (not shown).
The [0032] lapping plate portion 306 includes a lapping plate housing 330, a lapping plate cap 334, a lapping plate 336, and a pressure sensor 338. The lapping plate housing 330 includes a first cavity for threadily attaching the housing 330 to the shaft 324 of the shock 312. The lapping plate housing 330 includes a second cavity 340 that is sized to receive the lapping plate cap 334 and the lapping plate 336. The lapping plate 336 is suitably a half ball that is attached to the lapping plate cap 334. When the half ball and lapping plate cap 334 are inserted into the second cavity 340, cross-pins 344 are inserted along a cord of the swivel plate base 330 near the opening of the second cavity 340. The cross-pins 344 are separated at a distance that is less than the diameter of the half ball, thereby keeping the half ball within the second cavity 340. The pressure sensor 338 is mounted at one end of the second cavity 340 opposite the opening of the cavity 340. The pressure sensor 338 is attached to the controller device (not shown). The pressure sensor 338 senses pressure from the lapping plate cap 334 based upon pressure on the lapping plate 336 causing the lapping plate cap 334 to move within the cavity 340. The controller device instructs increases or decreases in pneumatic pressure within the pneumatic housing 310 based on the sensed applied load pressure compared to the prescribed pressure.

Multiple Unit

FIGS. [0033] 8A-C illustrate a multi-end effector support 350. The support 350 includes a plurality of arms 356 that extend radially from a center shaft 360. The center shaft 360 is attached to a base (not shown) that is coupled to the robot 42 (FIG. 1). The types of end effector units that can be used with the multi-end effector support 350 are any one of the ones shown in FIGS. 3-7. In order to accommodate the plurality of arms 356, multiple size lapping plates are interspersed and attached to the ends of each of the spring-loaded end effector units 240 attached to the arms.
It will be appreciated that various jointed end effectors can be used at the end of any of the spring-loaded shafts or at the end of the pneumatic shock. An example end effector that can be used is a cross-pinned ball socket joint end effector that is described in the related copending U.S. Patent Application identified above and incorporated by reference. [0034]
While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow. [0035]

Claims

What is claimed is:

1. A robotic system for lapping a surface, the robotic system comprising:

a robotic arm for applying pressure; and

a end effector unit including:

a base attached to the robotic arm;

a plate;

a lapping pad attached to the plate;

a pivot joint for allowing the plate to pivot about two orthogonal axes; and

a component for absorbing pressure applied to the end effector unit.

2. The system of claim 1, wherein the component includes a spring-loaded shaft.

3. The system of claim 1, wherein the component includes a pneumatic shaft.

4. The system of claim 3, wherein the component further includes a pneumatic sensor for sensing pressure applied to the plate.

5. The system of claim 1, wherein the two axes are substantially parallel to the planar surface.

6. The system of claim 5, wherein the two axes are substantially orthogonal to a direction of the pressure applied to the robot.

7. The system of claim 5, wherein the pivot joint includes a universal joint.

8. The system of claim 5, wherein the pivot joint includes a gimbaled joint.

9. The system of claim 5, wherein the pivot joint includes a needle bearing joint.

10. The system of claim 5, wherein the pivot joint includes a ball and socket joint.

11. The system of claim 10, wherein the ball and socket joint includes a half-ball and socket joint.

12. The system of claim 10, wherein the ball and socket joint includes a crossed-pin ball and socket joint.

13. A lapping end effector comprising:

a base;

a plate having a planar surface;

a lapping pad attachable to the planar surface of the plate; and

a pivot joint for allowing the plate to pivot about two axes, the pivot joint including a pressure absorbing component for absorbing a predetermined amount of pressure applied to the plate.

14. The system of claim 13, wherein the pressure absorbing component includes a spring.

15. The system of claim 13, wherein the two axes are substantially parallel to the planar surface.

16. The system of claim 15, wherein the pivot joint includes a universal joint.

17. The system of claim 15, wherein the pivot joint includes a hexagonal ball joint.

18. The system of claim 15, wherein the pivot joint includes a crossed-pin ball and socket joint.

19. A robotic system for lapping a surface, the robotic system comprising:

a robotic arm;

a support member coupled to the robotic arm; and

a plurality of end effector units including:

a base attached to the support member;

a plate having a planar surface;

a lapping pad attachable to the planar surface of the plate; and

a pivot joint for allowing the plate to pivot about two axes; and

one or more components for absorbing pressure applied to each end effector unit.

20. The system of claim 19, wherein the one or more components include a spring-loaded shaft.

21. The system of claim 19, wherein the one or more components include a pneumatic shaft.

22. The system of claim 19, wherein the one or more components include a spring.

23. A method for lapping a surface, the method comprising:

applying pressure by a robot between a lapping pad attached to a plate having a planar surface and the surface;

pivoting the plate to move about two axes, wherein the two axes are substantially parallel to the planar surface and the applied pressure is substantially orthogonal to the two axes; and

absorbing at least some of the applied pressure.