Integrating Product and Process Engineering Activities

1. Integrating Product and Process Engineering Activities Dr. Richard A. Wysk Leonhard Chair in Engineering The Pennsylvania State University University Park, PA 16802 rwysk@psu.edu http://www.engr.psu.edu/cim

2. Function, Cost, weight User, etc. Specification PRODUCT ENGINEERING Performance PLANNING DESIGN CONTROL Assemblies PRODUCTION ENGINEERING Parts Manufacturability Raw Materials Capabilities PROCESS ENGINEERING Engineering

3. A Vision of Integrated Engineering Systems (cont.) INTEGRATION ENGINEERING • tools and techniques that can be used to assist in combining planning, design, construction and management of a product.

4. Product, Process and Production Models Product Engineering Library of features Feature interactions Process Engineering Process / Feature links Inter-feature linkages Inter-process linkages Production Engineering System Specifics Machine Specifics Fixture Specifics Tool Specifics

5. A Simple IPPD Illustration

6. Process Dimensional Accuracy Positional Accuracy Drill (twist) .008 .005 + Reaming .0025 .005 + Bore (semi-finish) .0035 .0025 + Bore (Finish) .002 .002 + Integrating Design and Manufacturing Process Tolerance Chart -- limiting conditions

7. Generative Process Planning • Find the most efficient process capable • of obtaining the design specification. • Order the plans in an efficient manner. • Get parameters from a handbook. • Modify as required.

8. Table 2 Process Plan #1 for Case Study Bracket Operation Description Tooling V F d Time (ft/min) (in) (min) 10 load part into fixture .5 20 Drill large hole 300 .010 .21 .750 30 Drill small hole (8) 250 .008 1.70 .500 40 Unload and visually inspect 1.00 Total time 3.41 min p Dl t = m 12 fv p * . 750 * . 650 = .21min = 12.75sec t <large hole> = m 12 * . 010 * 60 . 0 p * . 5 * . 50 t = .2125min = 11.75sec each <small hole> = m 12 * 50 * . 008 A Traditional Process Plan

9. Process Dimensional Accuracy Positional Accuracy + ( 3 ) ( 3 ) s s + Drill (twist) .008 .005 + Reaming .0025 .005 + Bore (semi-finish) .0035 .0025 + Bore (Finish) .002 .002 + Process Tolerance Chart is really a Statistically-based Entity Process Tolerance Chart -- limiting conditions

10. Can we make some statistical inferences? (Size first) The likelihood that each hole size dimension is good is + 3 s (from Process tolerance chart). If all holes are normally distributed and independent, then P{>1 Bad hole dimension} = 1 - [P(good hole dimension)]no. of holes P{>1 Bad hole dimension} = 1 - .99739 = 1 - .976 = 2.4%

11. How about location? • All locations were specified RFS. • What does this mean? • Location requirements are independent of feature size

12. For RFS Features The likelihood of having a location out of spec becomes P[x < 0.750 - 0.008] + P[x>0.750+0.008] = P + P = P[z < -4.82] + P[z > +4.82] = 2*[1 - F(4.82)] =2*[1 - 0.9999774] =0.0000452

13. For all 9 holes P{Bad location} = 1 - (1 - .0000452)9 = 1 - .9996 = .0004

14. The Expected Part Cost Cp = cost to produce + warranty cost = $1.70 + P{defect} Cost of defect Assuming that the dimensional and location probabilities are independent we get P{good part} = [P{good dimension L good location}]no. of holes P{defective part} = 1 - P{good part} = 1 - [P{good dimension L good location}] no. of holes = 1 - [0.99739 * (1 - 0.0000452)]9 = .0244, and Cp = $1.70 + .0244 ($50) = $2.92 per part

15. Table 3 Process Plan #2 for Case Study Bracket Operation Description Tooling V f d Time (min) 10 Load part into fixture 47/64 0.5 20 Drill large hole .750 0 .010 1.70 30 Ream large hole 31/64 300 .010 .008 0.21 40 Drill small holes (8) .500 50 .010 50 Ream small holes (8) 250 .008 .008 1.70 40 Unload and visually inspect 1.00 Total time 5.32 min Does the Process planning process end here? An Alternative Process Plan

16. Process Dimensional Accuracy Positional Accuracy + ( 3 ) ( 3 ) s s + Drill (twist) .008 .005 + Reaming .0025 .005 + Bore (semi-finish) .0035 .0025 + Bore (Finish) .002 .002 + From the Process Tolerance Chart Process Tolerance Chart -- limiting conditions Choose either Reaming or boring to improve the quality of the product. Since reaming is a more efficient process, we will first look at it.

17. Calculating the percent defective =

18. Computing the likelihood of a bad part

19. What can we say about tradition Process planning procedures? • They do not take defects into account (based on costs). • Alternatives should be considered. • Procedure is easy to implement.

20. What if Position was specified as Maximum Material Condition? M M

21. What if the holes were specified as MMC? • Size dimension will be the same. • How about position? • Position is not independent of size.

22. Why is MMC important? Dm MMC Interchangeable fit and assembly is based on it. Dm LMC

23. Calculating Positional Defects It should be obvious that this value will be less than the RFS case.

24. Calculating proportion defective due to location

25. Proportion defective and cost

26. Is this the best plan? • Still don’t know • What about secondary processing activities? • Cost [additional processes] < Cost [warranty problems/piece]

27. SUMMARY AND CONCLUSIONS • Design for manufacturing is not well understood • In many cases, the devil is in the detail. • Statistical information is becoming more available and should be used as part of the design and planning process.