Precision Glass Moulding - Process

Process

The precision glass moulding process consists of six steps:

1. The glass blank is loaded into the lower side of the moulding tool.
2. Oxygen is removed from the working area by filling with nitrogen and/or evacuation of the process chamber.
3. The tool system is nearly closed (no contact of the upper mould) and the entire system of mould, die and glass is heated up. Infrared lamps are used for heating in most systems.
4. After reaching the working temperature, which is between the transition temperature and the softening point of the glass, the moulds close further and start pressing the glass in a travel-controlled process.
5. When the final thickness of the part has been achieved, the pressing switches over to a force-controlled process.
6. After moulding has been completed, the glass is cooled down and the working environment is filled with nitrogen. When the lens has cooled to the point where it can be handled, it is removed from the tool.

The process is executed on a specialized moulding machine, which precisely controls the temperature, travel, and force during the process. The tools used must withstand high temperatures and pressures, and need to be resistant to chemical interaction with the glass. The mold materials also have to be suitable for machining into the precise surface profiles.