altered images - thermal distortion of an overhead projector ray ellender elite consulting ltd
TRANSCRIPT
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
The Method
• Make Simplified Model• Correlate with Test• Understand the Mechanism• Brain Storm a Solution
– Short-Term
– Long-Term
Thermal Analysis
• Set Up Temp Loads• (Load as a Function
of Coordinates)• Correlate with
Measurements• Take Results into
Structure
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
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
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
Solutions ?Stiffer base - Ali Plate Underneath
• 3mm Ali Plate• Deflection Worse• Note Ali :
CTE = 2.3 x 105
SolutionsHigh CTE Plate Underneath
• PE Plate underneath• CTE = 15 x 105
• Deflection improved,
if high enough temp.
Solutions ‘Bimetallic Strip’
• Smaller Ali Plate• Bonded to ABS• Not so severe• Next step to Optimise
SolutionsLower Platten Surface
• Global Sensitivity• 12-17mm Depression
Is best• Virtually any amount
of depression is good
Angular Deflection v. Platten Depression
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 5 10 15 20 25
Platten Depression (mm)
Ang
ular
Def
n (d
eg)
SolutionsLower Platten Surface
• Leave middle of platten undepressed to mount Fresnel lens
• Details require further development