Thermographic characterization for surface finishing process development

Patent metadata

Field	Value
Publication number	US-9855637-B2
Application number	US-201514638892-A
Country	US
Kind code	B2
Filing date	Mar 4, 2015
Priority date	Apr 10, 2014
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

A method and system for observing and monitoring thermal characteristics of a machining operation, such as a surface finishing operation, performed on a workpiece is disclosed. The surface finishing operation can be performed on the workpiece in order to remove a surface defect, e.g. a parting line, on a surface of the workpiece and/or to provide a mirror-like finish to the workpiece. In one embodiment, an emissive layer is applied to the workpiece to increase a thermal emissivity of the workpiece. In some embodiments, a finishing surface, such as a polishing or buffing wheel, and/or a lubricant used in a finishing operation is monitored. A thermal profile of the surface of the workpiece, finishing surface and/or lubricant can be obtained. The finishing operation can be modified in response to the monitored thermal characteristics to prevent the occurrence of defects and improve the efficacy of the finishing operation.

First claim

What is claimed is:

1. A method for finishing a surface of a workpiece, the surface being modified with an emissive layer that comprises a metal oxide layer disposed on the surface of the workpiece, the method comprising:
performing a finishing operation by contacting and moving an abrasive surface relative to the surface of the workpiece, wherein a thermal characteristic of the workpiece changes during the finishing operation;
monitoring the changes of the thermal characteristic by monitoring a thermal radiation of the surface of the workpiece; and
adjusting a parameter of the finishing operation based on the monitored changes of the thermal characteristic to maintain the thermal characteristic within a predetermined range during the finishing operation.

2. The method of claim 1 , wherein monitoring the changes of the thermal characteristic further comprises monitoring a temperature of a second surface of the workpiece, the second surface being different than the surface of the workpiece on which the finishing operation is being performed.

3. The method of claim 1 , wherein monitoring the changes of the thermal characteristic further comprises monitoring thermal images of one or more of the surface of the workpiece, the abrasive surface and a lubricant used during the finishing operation.

4. The method of claim 3 , wherein the thermal images are formed by:
directing an infrared light at one or more of the surface of the workpiece, the abrasive surface and the lubricant,
measuring reflected infrared light reflected off one or more of the surface of the workpiece, the abrasive surface and the lubricant, and
collecting data related to the reflected infrared light.

5. The method of claim 1 , wherein monitoring the changes of the thermal characteristic further comprises monitoring changes in a color of a lubricant used in the finishing operation, the lubricant having an additive that changes color when a predetermined temperature is reached.

6. The method of claim 1 , wherein adjusting the parameter of the finishing operation comprises adjusting one or more of the following during the finishing operation:
a force of the abrasive surface applied to the surface of the workpiece,
an amount of lubricant applied between the abrasive surface and the surface of the workpiece,
a speed of the abrasive surface moving relative to the surface of the workpiece,
a temperature of the workpiece, and
an ambient temperature of air surrounding the workpiece.

7. A method of finishing a workpiece, the method comprising:
forming an emissive layer on an outside surface of the workpiece to increase an emissivity of the workpiece, wherein the emissive layer is a dyed oxide layer;
performing a surface finishing operation on the workpiece, wherein a temperature of the emissive layer changes during the surface finishing operation; and
monitoring an amount of thermal radiation emitted by the emissive layer during the surface finishing operation with a thermal imaging system, wherein the thermal imaging system is configured to distinguish temperature variations of the emissive layer.

8. The method of claim 7 , wherein the emissive layer has a durability such that the surface finishing operation does not substantially degrade the emissive layer.

9. The method of claim 7 , wherein a thermal conductivity of the emissive layer is substantially similar to a thermal conductivity of the workpiece.

10. The method of claim 7 , wherein the workpiece is a metal workpiece.

11. The method of claim 7 , further comprising:
detecting a thermal characteristic based on thermal radiation emitted during the surface finishing operation; and
modifying the surface finishing operation in response to detecting the thermal characteristic.

12. The method of claim 11 , wherein the thermal characteristic exceeds a threshold value based on historical results from previous surface finishing operations.

13. The method of claim 7 , wherein the workpiece is a plastic workpiece and the surface finishing operation is configured to remove an excess amount of plastic from the workpiece.

14. The method of claim 7 , further comprising:
applying a second emissive layer on a portion of a fixturing device configured to position the workpiece during the surface finishing operation; and
monitoring an amount of thermal radiation emitted by the second emissive layer with the thermal imaging system.

Assignees

• Apple Inc

Inventors

• Whipple Lucas Allen
• Lancaster-Larocque Simon Regis Louis
• Chan Collin D
• Fagan Christopher R
• Yan Vincent
• Theilacker Ian S
• Miehm Brian K
• Bharadwaj Shravan

Classifications

• B24B49/006

  taking regard of the speed · CPC title

• B24B49/16

  taking regard of the load · CPC title

• B24B49/14 Primary

  taking regard of the temperature during grinding · CPC title

• B24B49/12

  involving optical means · CPC title

• B24B37/015

  Temperature control · CPC title