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_at_psu.edu
• http//www.engr.psu.edu/cim

2
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
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
A Traditional Process Plan
9
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
• Pgt1 Bad hole dimension 1 - P(good hole
  dimension)no. of holes
• Pgt1 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
• Px lt 0.750 - 0.008 Pxgt0.7500.008
• P P
• Pz lt -4.82 Pz gt 4.82
• 21 - F(4.82)
• 21 - 0.9999774
• 0.0000452

13
For all 9 holes

• PBad location 1 - (1 - .0000452)9
• 1 - .9996 .0004

14
The Expected Part Cost

• Cp cost to produce warranty cost
• 1.70 Pdefect Cost of defect
• Assuming that the dimensional and location
  probabilities are independent we get
• Pgood part Pgood dimension L good
  locationno. of holes
• Pdefective part 1 - Pgood part
• 1 - Pgood
  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
Does the Process planning process end here? An
Alternative Process Plan
16
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 dont know
• What about secondary processing activities?
• Cost additional processes lt 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.