Claims
- 1. A method for compression molding microstructures comprising the steps of:
a) placing a substrate between the two halves of the mold b) rapidly heating at least a portion of the mold which has microfeatures to a predetermined temperature c) compressing the heated or being heated microfeatures of the mold into the substrate d) rapidly cooling the mold, opening the mold and removing a molded article. whereby heating only the local area where microfeatures are to be molded reduces cycle time and provides dimensional stability due to non participation of the rest of the bulk material in the deformation process.
- 2. The method of claim 1 wherein said heating comprising the steps of:
a) passing a substantially high frequency alternating electric current through a portion of said mold half b) passing the current through the other mold half thereby heating selective surface areas of the mold by said proximity effect to a predetermined temperature.
- 3. The method of claim 1 wherein said cooling is accomplished by passing a cooling medium to a portion of said mold.
- 4. The method of claim 3 wherein said cooling is accomplished rapidly by:
passing a cooling medium through a micro channel network that is located on the order of one millimeter below the inner surface of the molds whereby a rapid cooling reduces the cooling time of the molding cycle.
- 5. The method of claim 4 wherein the cooling medium is displaced before the heating cycle begins,
whereby avoiding the heating of the cooling medium during the heating phase reduces the heating time and energy.
- 6. The method of claim 5 wherein the cooling medium is displaced by the pressure gradient of a gas.
- 7. The method of claim 6 wherein the displacing gas is air.
- 8. The method of claim 2 wherein the substantially high frequency alternating electric current is between 50 Hz to 100 MHz.
- 9. An apparatus of mold for compression molding objects, comprising:
a) means for providing insulation layers that electrically isolates said portion of mold halves from the rest of the machine and allowing the magnetic flux generated by said current to pass through said insulation layers b) means for providing electrical connections from a high frequency power supply to said portion of mold half and then to a portion of the other mold half and back to the high frequency power supply.
- 10. The mold of claim 9 wherein said portion of the mold is made of materials with a selective magnetic permeability to achieve a selective said skin layer thickness.
- 11. The mold of claim 9 wherein said portion of the mold is placed in juxtaposition with magnetic materials such as magnetic core to confine the skin thickness.
- 12. The mold of claim 9 wherein said portion of the mold has thermal insulation whereby said thermal insulation provides energy efficiency in heating said portion of mold surface.
- 13. The mold of claim 12 wherein said thermal insulation is comprised of any combination of metal oxide layer, polymeric materials, or porous materials.
- 14. The mold of claim 12 wherein said metal oxide layer is Zirconium Oxide.
- 15. The mold of claim 12 wherein said thermal insulation consist of air gap and ribs to support the mechanical load and minimize the deflection between the ribs.
- 16. The mold of claim 12 wherein the cooling channel is placed within said mold.
- 17. The mold of claim 12 wherein the cooling channels are located near the back of the surfaces of said mold
whereby said cooling channels conforming to the cavity aids uniform cooling.
- 18. The mold of claim 17 wherein the size of cooling channel gap, the ribs between the channels, and the thickness of the mold surface are between 0.05 mm to 20 mm.
- 19. The mold of claim 9 wherein a parasitic induction coil is attached for the purpose of increasing the inductance.
BACKGROUND—STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] Research leading to the invention disclosed and claimed herein was supported in part by the National Science Foundation, NSF Grant No. DMI-9713519. The U.S. Government may have certain rights to the invention.