1. Altered Images - Thermal Distortion of an Overhead Projector Ray Ellender Elite Consulting Ltd.

2. Company Engineering Consultancy in UK Office in Northampton Long-Time Mechanica Users CEP’s, Structure & Motion Specialise in Mechanica-based FE and Dynamics Consultancy General Engineering Problem Solving Design and Project Management PTC Functional Simulation Resellers Pro/Mechanica and Pro/E Training

3. The Problem New Design of Reflective OHP Thermal Distortion of Base Distortion of Image

4. The Method Make Simplified Model Correlate with Test Understand the Mechanism Brain Storm a Solution –Short-Term –Long-Term

5. The Model Simple Mechanica Model Deflection Measures

6. Thermal Analysis Set Up Temp Loads (Load as a Function of Coordinates) Correlate with Measurements Take Results into Structure

7. Structural Analysis Set Up Baseline Analysis Correlate with Measurements Review Results

8. Understand the Problem Hotter at Top than Bottom Platten Expands more than ‘Ground’ Level Therefore Get Bowing of the Base Takes Arm Support with it

9. Potential Solutions - 1 Reduce Temperature –Reduce Heat InputTried - works –Insulate BaseNot very good –Conduct Heat AwayNot tried Change Material – Lower CTE Tried - works Stiffen Base Didn’t work Cut out most of Platten Didn’t work

10. Potential Solutions - 2 Isolate Arm Base from Platten (Hinge)Didn’t work Mount Arm to Ali Plate & Control Plate MovementNot good enough Modify Geometry (Lower Platten)Worked well Make Lower Plate High CTEWorked Bond Low CTE to Platten (Bimetallic Strip)Worked too well

11. Solutions Reduce Temperature Reduce Temp from 60 o to 45 o Improvement As expected

12. Solutions Reduce CTE CTE reduced from 10 x 10 5 (ABS) to 7.3 x 10 5 (PC/ABS) Works as expected

13. Solutions ? ‘Hinge’ Hinge to Isolate Arm Mtg Area Didn’t Work

14. Solutions ? Stiffer base - Ali Plate Underneath 3mm Ali Plate Deflection Worse Note Ali : CTE = 2.3 x 10 5

15. Solutions High CTE Plate Underneath PE Plate underneath CTE = 15 x 10 5 Deflection improved, if high enough temp.

16. Solutions ‘Bimetallic Strip’ 1mm Ali Plate attached to Platten (2.3 x 10 5 CTE) Works too well

17. Solutions ‘Bimetallic Strip’ Smaller Ali Plate Bonded to ABS Not so severe Next step to Optimise

18. Solutions Lower Platten Surface Lower by 15mm Much Improved Long Term Solution To be Optimised

19. Solutions Lower Platten Surface Global Sensitivity 12-17mm Depression Is best Virtually any amount of depression is good

20. Solutions Lower Platten Surface Leave middle of platten undepressed to mount Fresnel lens Details require further development

21. Summary 24 Runs in 3 days Wide Range of Different Solutions Thermal Solution often Counter-intuitive Concept Model enabled Solutions to be found quickly Short & Long Term Solutions found