Use of infrared radiation in molding of protective caps
View Patent ↗The invention is a method of a sheet ( 134 ) of thermoplastic material between upper and lower molds ( 102, 104 ), heating the sheet to a plastic state using electromagnetic radiation and molding the sheet. The molds ( 102, 104 ) are preferably formed of silicon and infrared radiation is preferably used to heat the sheet ( 134 ).
1. A method of molding including:
a) providing an upper mold and a lower mold, at least one of which is formed substantially of silicon or silicon alloy and which is at least partially transparent or translucent to electromagnetic radiation at one or more wavelengths in the infrared range, the upper and lower molds together or separately defining one or more cavities when said upper and lower molds are brought into contact with each other;
b) providing a sheet of thermoplastic material between said upper and lower molds, said thermoplastic being at least partially absorbing of electromagnetic radiation at said one or more wavelengths;
c) pressing the sheet between the first and second molds;
d) during said pressing step, heating substantially the entire sheet by radiating the sheet with electromagnetic radiation at said one or more wavelengths through the mold or molds at least partially transparent or translucent to electromagnetic radiation at said one or more wavelengths, the combination of heat and pressure causing the sheet material to flow into the one or more cavities; maintaining said sheet between said first and second molds after completion of the heating step to cool said sheet, said sheet thereby substantially retaining a molded shape.
2. The method of claim 1 wherein both said molds are both formed substantially of silicon or silicon alloy and are at least partially transparent or translucent to electromagnetic radiation at said one or more wavelengths.
3. The method of claim 1 wherein the sheet intrinsically absorbs electromagnetic radiation at said one or more wavelengths.
4. The method of claim 1 wherein the sheet includes dopants which absorb electromagnetic radiation at said one or more wavelengths.
5. The method of claim 1 wherein the sheet includes carbon as a dopant to absorb electromagnetic radiation at said one or more wavelengths.
6. The method of claim 1 wherein said one or more wavelengths are in the range of 1000 nm to 5000 nm.
7. The method of claim 1 wherein at step c) the sheet is additionally heated by conduction.
8. A method of molding including:
a) providing an upper mold and a lower mold, at least one of which is formed substantially of silicon or silicon alloy and which is at least partially transparent or translucent to electromagnetic radiation at one or more wavelengths in the infrared range, the upper and lower molds together or separately defining a plurality of discrete cavities when said upper and lower molds are brought adjacent each other;
b) providing a sheet of thermoplastic material between said upper and lower molds, said thermoplastic being at least partially absorbing of electromagnetic radiation at said one or more wavelengths;
c) heating the sheet by radiating the sheet with electromagnetic radiation at said one or more wavelengths through the mold or molds at least partially transparent or translucent to electromagnetic radiation at said one or more wavelengths to cause the sheet material to flow into the cavities thereby separating the sheet into a plurality of discrete objects.