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Serveral Approaches that Use the Tolerance Specification in CAPP

Serveral Approaches that Use the Tolerance Specification in CAPP. 1998. 8/25. 화 이정철. Automated setup selection in feature-based process planning. H.-C.Wu and T.-C. Chang - School of Industrial Engineering, Purdue University, West Lafayette, USA.

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Serveral Approaches that Use the Tolerance Specification in CAPP

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  1. Serveral Approaches that Use the Tolerance Specification in CAPP 1998. 8/25. 화 이정철

  2. Automated setup selection in feature-based process planning H.-C.Wu and T.-C. Chang - School of Industrial Engineering, Purdue University, West Lafayette, USA. - Int. J. PROD. RES. 1998, VOL. 36, NO. 3, 695-712 08/25/98 2/19

  3. Content • Introduction • Overview of the quick turnaround cell(QTC) • Optimum setup planning based on position tolerances • Consideration of other geometric tolerances • Examples and results • Conclusions • References 08/25/98 3/19

  4. 1. Introduction(1/3) • Two categories of tolerance analysis • Assembling tolerance • Operation tolerance • 현재대부분의시스템의한계 • Process plan  tolerance chain analysis • The tolerance relaionships between feature are not considered. • select datums arbitarily.  Infeasibility, Cost의증가 08/25/98 4/19

  5. 1. Introduction(2/3)- tolerance spec. 사용에대한기존연구 • Boerma and Kais(1988) • Setup과fixture 선택시tolerance spec. 사용. • Zhang and Mei(1995) • Datum과setup 선택시tolerance spec. 사용. • ODTAA(operational dimension and tolerance analysis algorithm): NC based approach. • Sarma and Wright(1996) • Milling process에서setup과tool change를최소화하는알고리즘제안. • Precedence constraints가주관심 08/25/98 5/19

  6. 1. Introduction(3/3)- 논문의목적 • Suggest an approach that • Analyze the tolerance spec. of workpiece • With explicit datum elements • Generate feasible or optimum setup plan. • Quick turnaround cell(QTC) • 논문에서제안된접근방법으로실제구현된시스템. • An integrated CAD/CAM system 08/25/98 6/19

  7. 2. Overview of the QTC- Main modules of the QTC Feature-based, OO design CSG and B-rep solid models ANSI compatible tolerance representation feature refinement (design to mfg. Features) Generative process planning and automatic fixture planning NC simulation Cutter path verification Design System Geometric Reasoning Process Planning NC Programming 08/25/98 7/19

  8. 3. Optimum setup planning based on position tolerances 3.1. Position tolerance between features(1/2) 선택된tool: 0.745``-0.758`` RFS(Regardless Feature Size) MMC(Maximum Material Condition) Figure 1. Tolerance zones of a hole at different material conditions 08/25/98 8/19

  9. 3. Optimum setup planning based on position tolerances 3.1. Position tolerance between features(2/2) Figure 2. Tolerance zones of a pocket at different material conditions 08/25/98 9/19

  10. 3. Optimum setup planning based on position tolerances3.2. Errors stack up in machining operations(1/3) Figure 3. Four possible setups in each tool approach direction 08/25/98 10/19

  11. 3. Optimum setup planning based on position tolerances3.2. Errors stack up in machining operations(2/3) (a) setup 1 Figure 4. Tolerance stack-up of the hole in the X direction in (a) setup 1 and (b)setup 4 08/25/98 11/19

  12. 3. Optimum setup planning based on position tolerances3.2. Errors stack up in machining operations(3/3) (b) setup 4 Figure 4. Tolerance stack-up of the hole in the X direction in (a) setup 1 and (b)setup 4 08/25/98 12/19

  13. 3. Optimum setup planning based on position tolerances 3.3. Algorithm of optimum setup planning • Step 1: To determine the tool approach direction(s) of each feature.  feature refinement process in QTC • Step 2: To calculate the minimum number of setups with the most accurate position relationship between features. • Step 3: To generate other plans in each approach direction and to report them to the fixture planner for fixture selection. 08/25/98 13/19

  14. 4. Consideration of other geometric tolerances • Perpendicularity, angularity, parallelism, etc. • The value of many geometric tolerances is sensitive to the dimensions of the feature it applied to. Figure 5. A parallelism tolerance applied to a side of the slot. 08/25/98 14/19

  15. 5. Examples and results(1/3) Figure 6. Two partial views of the part(some tolerance specs. Are omitted). (a) Features in approach direction -Z. (b) Feature in approach direction Z. 08/25/98 15/19

  16. 5. Examples and results(2/3) Figure 7. The optimum setup plan 08/25/98 16/19

  17. 5. Examples and results(3/3) Figure 8. The next best setup plan 08/25/98 17/19

  18. 6. Conclusions • An algorithm that selects datums for a setup arrangement based on design tolerances is presented. • The optimum setup plan is the one that uses the fewest number of setups to machine all the features • 추후연구 • Expanding the feature domain. • More precise tolerance analysis technique. • Better operation error estimation. • Wider geometric tolerance coverage. 08/25/98 18/19

  19. Reference • Zhang, H.C., and Mei, J., 1995, Automated tolerance analysis for CAPP system, Int. J. of Advanced Mfg. Tech., 10, 249-224. • Nanua, S., 1996, Systems approach to computer-integrated and Mfg., 153-192. • Jae Yeol Lee and Kwangsoo Kim, 1996, Geometric reasoning for knowledge-based parametric design using graph representation, Computer-aided design, Vol. 28, No. 10, 831-841. • Peter, C.C., and Rajit, G., 1996, Feature-based approach for set-up minimization of process design from product design, Computer-aided design, Vol., 28, NO. 5, 321-332. 08/25/98 19/19

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