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Experimentation for Heating Parameter Design and PMMA Characterization on a Hot Embossing Set-up

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).

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Experimentation for Heating Parameter Design and PMMA Characterization on a Hot Embossing Set-up

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  1. Experimentation for Heating Parameter Design and PMMA Characterization on a Hot Embossing Set-up

  2. 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.

  3. 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.

  4. Experimental Setup (Cont..)

  5. Water inlet 3.65” Water outlet 4 9 13 3 8 12 10.00” 7 2 6 11 1 5 10 Thermal Analysis (Heating) Temperature distribution for the experimental block with two heating cartridges Thermocouple locations on the block

  6. Temperature Profile (Heating) Comparison of temperature profile obtained at location 7 from thermal analysis and experimental data

  7. Temperature Difference (Heating) Temperature difference plot between thermocouple locations 8 and 3

  8. Temperature Profile (Cooling) Temperature profile at thermocouple location 7 during cooling (volume flow rate of 0.52 gpm of water)

  9. Temperature Difference (Cooling) Temperature difference plot between thermocouple locations 1 and 4

  10. 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.

  11. Important Embossing Parameters • Temperature of embossing Viscosity of the polymer is directly proportional to the temperature. • Pressure Embossing pressure depends on the depth of embossing. • Speed of embossing Speed of embossing controls flow of the polymer.

  12. 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.

  13. Stress-Strain Curve Stress-Strain curve for PMMA obtained using a cylindrical tool of 1” diameter

  14. E variation with Temperature Variation of Young’s Modulus with temperature obtained using two different tool sizes

  15. Specimen Pictures

  16. 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.

  17. Future Work Polymer behavior • Williams-Landel-Ferry (WLF) equation • Time to fill a cavity • Polymer flow during Embossing

  18. Hot Embossing Machine

  19. 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.

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