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A Study of Scratch Formation from Random Orbit

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A Study of Scratch Formation from Random Orbit A STUDY OF SCRATCH FORMATION FROM RANDOM ORBIT SANDING OF WOOD SURFACES: INFLUENCES OF WOOD SPECIES, ROTATION SPEEDS AND GRIT SIZES By XIUZHE MENG Submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Electrical Engineering and Computer Science CASE WESTERN RESERVE UNIVERSITY May 2020 Table of Contents Acknowledgment....................................................................................................................9 Abstract................................................................................................................................. 10 Chapter 1 introduction.........................................................................................................12 1.1 Background and Motivation..................................................................................12 1.2 Related Work.......................................................................................................... 17 1.3 Companion Thesis..................................................................................................20 Chapter 2 Instrumentation.................................................................................................. 21 2.1 Random Orbit Sander............................................................................................21 2.2 Securing the Sample.............................................................................................. 22 2.3 Lighting for Sample Inspection.............................................................................23 2.4 Applied Force Measurement.................................................................................23 2.5 Ambient Temperature Measurement...................................................................24 2.6 Sensing Circuit Block..............................................................................................25 Chapter 3 Experimental....................................................................................................... 26 3.1 Samples and Grit Sizes...........................................................................................26 3.2 Experiment Procedure........................................................................................... 27 3.3 Data Collection and Analysis.................................................................................28 3.4 Scratch Severity Scoring........................................................................................ 32 Chapter 4 Data Analysis.......................................................................................................34 2 4.1 Room Temperature................................................................................................34 4.2 Applied Force on the Sander................................................................................ 35 4.3 Surface Roughness.................................................................................................39 4.4 Severity of Scratches.............................................................................................. 40 Chapter 5 Conclusion...........................................................................................................52 Appendix............................................................................................................................... 54 References.............................................................................................................................59 3 List of Tables Table 1 . Wood density (lb per ft3) and Janka hardness (lbf) for the wood species in this study........................................................................................................... 27 Table 2 . The results of the F-test............................................................................... 32 Table 3 . Scoring method for the severity of scratches............................................ 33 Table 4 . Room temperature (in oC) measured during the experiments herein.... 34 Table 5 . Applied force (in N) measured in the 1st set of poplar experiments.......35 Table 6 . Applied force (in N) measured in the 2nd set of poplar experiments.....36 Table 7 . Applied force (in N) measured in the 3rd set of poplar experiments......36 Table 8 . Applied force (in N) measured in the 1st set of pine experiments.......... 37 Table 9 . Applied force measured in the 2nd set of pine experiments................... 37 Table 10 . Applied force measured in the 3rd set of pine experiments..................37 Table 11 . Applied force (in N) measured in the 1st set of oak experiments......... 38 Table 12 . Applied force (in N) measured in the 2nd set of oak experiments........38 Table 13 . Applied force (in N) measured in the 3rd set of oak experiments.........38 Table 14 . Applied force (in N) measured in the purple heart experiments........... 39 Table 15 . Spherical test results on independence of selected variables................41 Table 16 . The severity of scratches in the 1st set of poplars experiments.............42 Table 17 . The severity of scratches in the 2nd set of poplars experiments........... 42 Table 18 . The severity of scratches in the 3rd set of poplars experiments............42 4 Table 19 . The averages for the poplar scratch severity data in Tables 16-18.......42 Table 20 . F-test results of poplar experiments based on ANCOVA.......................43 Table 21 . The severity of scratches in the 1st set of pine experiments..................45 Table 22 . The severity of scratches in the 2nd set of pine experiments................ 45 Table 23 . The severity of scratches in the 3rd set of pine experiments................. 45 Table 24 . The averages for the pine scratch severity data in Tables 21-23.......... 45 Table 25 . F-test results of pine experiments based on ANCOVA.......................... 46 Table 26 . The severity of scratches in the 1st set of oak experiments................... 48 Table 27 . The severity of scratches in the 2nd set of oak experiments..................48 Table 28 . The severity of scratches in the 3rd set of oak experiments.................. 48 Table 29 . The averages for the oak scratch severity data in Tables 26-28............48 Table 30 . F-test results of oak experiments based on ANCOVA............................49 Table 31 . The severity of scratches in the purple heart experiments..................... 49 Table 32 . F-test results of purple heart experiments based on ANCOVA.............50 5 List of Figures Figure 1 . Cutting action of abrasive grains.(from [6]).............................................. 13 Figure 2 . Aluminum oxide grit 280 (36 micron particle size) at 200x magnification.(from [6])........................................................................................ 14 Figure 3 . Crescent-shaped scratches in random orbit sanding..............................16 Figure 4 . A photo of the Ridgid R2611 Random Orbit Sander used in this study.21 Figure 5 . A photo of a pair of DEWALT DWHT83139 bar clamps.......................... 22 Figure 6 . A photo of a Husky 2000 lumen portable LED work lamp......................23 Figure 7 . A photo of the 19 mm (0.75 inch) diameter Tactilus force sensor. ....... 24 Figure 8 . A photo of the force sensor mounted on the sander..............................24 Figure 9 . A photo of the DS18B20 temperature sensor.......................................... 24 Figure 10 . A schematic of the sensor system........................................................... 25 Figure 11 . Resistance-force correlation for the force sensor.(from [22])...............29 Figure 12 . Photos showing comparisons of samples before (above row) and after (below row) sanding—from left to right, poplar, pine, oak and purple heart.40 Figure 13 . A plot of the poplar data in Table 19...................................................... 43 Figure 14 . A plot of the pine data in Table 24..........................................................46 Figure 15 . A plot of the oak data in Table 29........................................................... 49 Figure 16 . A plot of the purple heart data in Table 31............................................ 50 Figure 17 . The average scratch severity scores from the experiments for poplar, 6 pine, oak and purple heart as a function of grits size and sander speed........51 7 List of Equations 3662 F 1.436 28.98 R ..................................................................................................... 29 Y XB U ....................................................................................................................29 Y u a b (X u ) e ijk i j e ijk x ijk ..............................................................................30 between - group variability F(n) within - group variability ..............................................................................30 SST SSA SSE SSX ................................................................................................31 8 Acknowledgment During this thesis study, I received valuable help from many people. Their inputs helped me to complete the thesis. I would like to take this opportunity to express my heartfelt thanks to all who helped. The person I am most thankful to is my advisor Professor Mehran Mehregany. He led me through all stages of writing this thesis and provided careful reviews. This thesis could not have reached its conclusion without his rigorous and enlightening guidance. Secondly, I
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