Bench-Top Precision Glass Molding (PGM) Machine

Moore Nanotechnology Systems LLC. and Toshiba Machine CO. are two suppliers for glass molding machines in the US and both have designed their machines to be compatible with medium to large volume production of optics. Scientific research has a need for a smaller, bench-top sized version of these machines with flexibility in machine design optical component geometries and process parameters. The GP-5000HT precision glass molding machine as shown in below figure from Dyna Technologies Incorporated (DTI) was designed for this purpose. The main objective of this study is to define the machine’s functionality and measure the accuracy of the new design’s control over thickness of pressed or molded lenses, an attribute (commonly described at center thickness, CT) which is critical in lens manufacturing.

Friction Measurement in Precision Glass Molding (PGM)

Measuring experimentally the static and dynamic friction coefficient between hot glass and mold material is the first step for friction charactrization under conditions similar of the PGM process. The apparatus designed for this research encompasses a wide range of friction coefficient measurement between different glass and mold materials at elevated temperatures. The effect of different coating, temperature, material, and normal force on the friction force is measured. The data obtained from this measurement can be used in the FEA of the PGM process to predict the desired mold geometry more precisely.

Micro injection Molding

The micro-injection molding process has a smaller processing window compared to traditional injection molding, with the filling time and packing time normally being much shorter. This presents the difficulty in controlling and monitoring the entire molding process. The process is also more susceptible to slight changes in process parameters such as mold temperature, injection velocity, metering size, and packing pressure. Therefore, good process repeat-ability and a high-quality mold are essential in order to achieve consistently high quality micro-parts.

Micro-injection molding is not just about scaling down part size. Issues such as changes in molding capability of micro-features and freezing time arise when the part geometry is reduced in size. Scaling down the process
from the conventional injection molding process also involves changes in the molding process and mold design. One example in terms of process changes is the application of higher melt temperature and higher injection velocity, and the introduction of cyclic mold heating process to prevent premature freezing due to the high surface area to volume ratio of micro-parts.

The focus of this research was employing cavity pressure to determine its robustness as indicator of part quality and process behavior for different polymeric material. Viscoelasticity effect versus viscosity was investigated as an important parameter in cavity pressure monitoring.