Precision Glass Molding

Precision glass molding /or moulding / (PGM) is a replicative process that allows the production of high precision optical components from glass without grinding and polishing. PGM is used to manufacture precision glass lenses for consumer products and the main advantage over mechanical lens production is that complex lens geometries such as aspheres can be produced cost-efficiently. In PGM process , a glass blank heated to the thickly flowing state is molded to the desired shape using a molding tool. The replicative character of the molding tools transfer the surface specifications of the die to the glass lens, so that time-consuming grinding and polishing processes are needed only during tool making.

PLANT FOR OPTICS has built new production facility for the replicative fabrication of precision glass optics using glass mold press machine GMP-311V(CE) (vacuum type) from Toshiba Machine Co. Ltd. (TMC) . The machine is working in clean room environment (class 10 000 or less) to avoid any dirty contaminations over molded lenses and on the molding tools during the precision molding.

PLANT FOR OPTICS collaborate with Aixtooling GmbH for comprehensive consulting services related to the precision molding of optical glass. Aixtooling are the European service provider for Toshiba GMP series machines and they provide us integrative technology consulting on-site , complex technical problem solving and making of molding tools.

Molding process flow simplified in 8 steps:
Step 1 Set glass material (ball lens ,gob or near net shape) onto molds
Step 2 Vacuuming inside of the chamber
Step 3 Purging inside of the chamber with nitrogen gas (N2)
Step 4 Heating mold dies and glass material to specified transformation temperature Tg
(Tg =400 to 800 °C depends on glass type) making isothermal molding conditions.
Step 5 Vacuuming inside of the chamber
Step 6 Clamping upper and lower tools together, with a pressure force of up to 30 kN and pressing glass material
Step 7 Cooling down mold dies and molded lens with nitrogen gas and the tools move apart
Step 8 Unloaded molded lens after cooling to the specified temperature

Molded lenses are inspected under microscope for surface imperfections in the clean room and then lenses pass dimension measurements, profiling of aspherical surfaces and measurement of centration error.

Main specifications of Toshiba Molding Press Machine GMP-311V(CE) :
Die-Molding Fix System with two sets of mold die holders:
– standard 110mm outer diameter mold die holder
– spare 64mm outer diameter mold die holder
Heating unit with 12 infrared lamps

Maximum heating temperature 800 degree Celsius
Press Axis Drive Unit:
– Press axis stroke 85mm
– Control range of Pressing force : +0.2kN ~ +30kN
– Driving speed for Lower Axis : 1 – 750mm/min.
– Position repeatability : Less than +/-0.003mm
– Tilt Specifications : 30seconds (0.0145mm)
– Servo Motor, Warm Jack and Load Cell

Piping Systems:
– Nitrogen (N2) Gas Piping Line
– Air Piping Line
– Cooling Water Piping Line
– Vacuum Piping Line with Rotary Pump for first rough vacuum and Turbo Molecular
– Vacuum Pump for high vacuum with ultimate pressure less than 6 x10-1 Pa
Control Unit : TOSNUC 80-GMP

Cementing and assembling

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