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Elite Consulting Ltd.

Elite Consulting Ltd. Altered Images - Thermal Distortion of an Overhead Projector Ray Ellender. Company. Engineering Consultancy in UK Office in Northampton Long-Time Mechanica Users CEP’s, Structure & Motion Specialise in Mechanica-based FE and Dynamics Consultancy

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Elite Consulting Ltd.

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

  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 Input Tried - works • Insulate Base Not very good • Conduct Heat Away Not 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 Movement Not good enough • Modify Geometry (Lower Platten) Worked well • Make Lower Plate High CTE Worked • Bond Low CTE to Platten (Bimetallic Strip) Worked too well

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

  12. SolutionsReduce CTE • CTE reduced from 10 x 105 (ABS) to 7.3 x 105 (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 105

  15. SolutionsHigh CTE Plate Underneath • PE Plate underneath • CTE = 15 x 105 • Deflection improved, if high enough temp.

  16. Solutions‘Bimetallic Strip’ • 1mm Ali Plate attached to Platten (2.3 x 105 CTE) • Works too well

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

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

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

  20. SolutionsLower 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

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