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ADCATS CASE STUDY:

ADCATS CASE STUDY:. Angular Variation in a Cellular Phone Display. By : Kenneth W. Chase & Alan J. Mortensen. BYU: January, 2001. Sponsored by and presented with permission from:. The Problem:. Skew between the LCD display and Lens artwork. Affects: Appearance

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ADCATS CASE STUDY:

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  1. ADCATS CASE STUDY: Angular Variation in a Cellular Phone Display

  2. By: Kenneth W. Chase & Alan J. Mortensen BYU: January, 2001 Sponsored by and presented with permission from:

  3. The Problem: Skew between the LCD display and Lens artwork. Affects: • Appearance • Customer confidence in quality LCD Display 345-6789* Lens Artwork *numbers superimposed on image

  4. Analysis Approach • Review Assembly • Create Simplified Model • Analyze Constraints • Calculate Assembly Tolerance (skew) • Results and Recommendations Demonstrate 1-D Excel Solver

  5. Task 1: Review Assembly

  6. Assembly Photos: Front Case Lens Outside Inside Electronics Artwork (permanent decal) Gasket LCD PCB

  7. Assembly Photos: Front Case Lens Outside Inside Electronics Loose Artwork placement is process controlled Lens is held by adhesive Slot/Hole 2 Pins

  8. Display to Lens Artwork Assembly Graph:

  9. Task 2: Create Simplified Model

  10. Display to Lens Artwork Simplified Assembly Graph:

  11. Range of rotation determined by clearance 1-D Stack of angular variation between components Skew between Lens Artwork & Display No vector loop required because: There are no kinematic joints Only analyzing rotation Simplified Model:

  12. Task 3: Analyze Constraints Identify critical features controlling angular variation

  13. Features Analyzed: • Pin Positioning -Side-to-side relation -How far pins seat in holes • Interference between Gasket & Display -Could prevent proper seating of pins

  14. Pin Positioning: Process-Dependant Consideration < a) Deterministic angle b) Random angle Force Closed Assembly Random Location in Clearance **Cell PhoneApplication: Gasket fixes it in random position

  15. Pin Positioning: General Case • Side-to-side Consideration d2 > d1 P2 Contacts on Right d2 < d1 P2 Contacts on Left

  16. Pin Positioning:Hole vs. Slot 2 Pin / 2 Hole 2 Pin / Hole & Slot Nominal Position Extreme Position Angular Displacement

  17. Gasket/Display Interference: Requirements for pin self-alignment: • C1 > C2 • C3  0, before the gasket makes contact

  18. Gasket/Display Analysis: C6 C2

  19. Predicted range: -0.23 to +0.11 (RSS) • Gasket will sometimes not seat on display glass • Centering of pins affected by too much interference Gasket/Display Analysis: Interference between the Display & Gasket (*Negative value desired ) C2

  20. Predicted range: -0.96 to -0.62 (RSS) • Full pin diameter enters the hole before the gasket contacts Gasket/Display Analysis: Pin shoulder depth in hole when the gasket first seats C6

  21. Task 4: Calculate Assembly Tolerance (skew)

  22. Example: 2Pin/2Hole Equivalent Angle: Angular variation for each contributing process variation

  23. } Desired Skew limits:±0.78 º 2.70 assembly process quality level 3 limits from Tolerance:±0.87 º Angular Variation (3):

  24. +2.7 -2.7 ±2.7: 99.31% 6940 Angular Variation 3: +3 -3 %YieldRejects/million ±3: 99.73% 2700

  25. sasm sasm 6 Variation Defined: RSS: 6s: where Cpk = Cp(1-k)

  26. Angular Variation (6):

  27. Task 5: Results & Recommendations

  28. Angular Variation 6:

  29. Conclusions: • Tolerance analysis shows areas of concern • Possible redesign and tolerance allocation will allow improved results

  30. Advantages: • Gasket always seats with pins centered • Angular variation is decreased (clearance B<A) • No need to bottom out the pin in the hole Suggested Redesign: Present Design Suggested Redesign

  31. 1-D Analysis in Excel: • Enter inputs values and assembly specifications.

  32. 1-D Analysis in Excel: • Review Reports: Stack-Up, Assembly Quality

  33. 1-D Analysis in Excel: 3. The Assembly Distribution is automatically generated

  34. Questions?

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