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Experimentation for Heating Parameter Design and PMMA
Characterization on a Hot Embossing
Set-up
Heating Experiments
Objective : Check uniformity of heating. Record the time to heat a block to a certain
temperature (200 deg C). Compare experimental results (uniformity and
time) with ANSYS analysis. Extrapolate results for the original heating
blocks.
Experimental Setup
Heating mode: Heating cartridges (Power 1kW).
Specimen : Two-hole and four-hole blocks.
Temperature sensor : J type Thermocouple.
Data Acquisition and monitoring: LabVIEW.
Miscellaneous : Relays, power source, etc.
Experimental Setup (Cont..)
Thermal Analysis (Heating)
3.65”
10.00”
Water inletWater outlet
1
2
3
4
5
6
7
8
9
10
11
12
13
Temperature distribution for the experimental block with two heating cartridges Thermocouple locations
on the block
Temperature Profile (Heating)
Comparison of temperature profile obtained at location 7 from thermal analysis and experimental data
Temperature Difference (Heating)
Temperature difference plot between thermocouple locations 8 and 3
Temperature Profile (Cooling)
Temperature profile at thermocouple location 7 during cooling (volume flow rate of 0.52 gpm of water)
Temperature Difference (Cooling)
Temperature difference plot between thermocouple locations 1 and 4
PMMA Characterization
Objective : Obtain stress-strain curves for Poly methyl
methacrylate (PMMA) at different temperatures.
Calculate Young’s modulus from the available data.
Find glass transition temperature PMMA.
Important Embossing Parameters
Temperature of embossingViscosity of the polymer is directly proportional to the temperature.
PressureEmbossing pressure depends on the depth of embossing.
Speed of embossingSpeed of embossing controls flow of the polymer.
PMMA Properties Stress strain curves are nonlinear. Glass transition temperature has significant
effect in properties of PMMA. At elevated temperatures:
Modulus (Compressive) values drop. Compressive strength drops. Creep effects increase.
Stress-Strain Curve
Stress-Strain curve for PMMA obtained using a cylindrical tool of 1” diameter
E variation with Temperature
Variation of Young’s Modulus with temperature obtained using two different tool sizes
Specimen Pictures
Conclusions
Experiments show good temperature uniformity on the experimental block.
Experimental temperature profile and simulation (ANSYS) profile are similar.
E values for PMMA drops with temperature.
E drops substantially after 105 deg C indicating the glass transition temperature.
Williams-Landel-Ferry (WLF) equation
Time to fill a cavity
Polymer flow during Embossing
)(
)(log
)(
00
0
02
01
T
T
TTC
TTC
Future Work
20
2
20 11
2 hhp
St
ff
Polymer behavior
Hot Embossing Machine
Mini-Vacuum Chamber Mini vacuum chamber used to provide a clean
and moisture free environment during embossing. Mini vacuum chamber can accommodate an 8”
substrate.