An Introduction to Plastic Gears :: essays papers

An Introduction to Plastic Gears As an employee of a world-class plastic gear manufacturer for many years, I see how this is an undeniably growing part of the gear industry. I hope to briefly describe how something seemingly simple as a plastic gear requires the culmination of many very state-of-the-art processes. Within one word I’ll say that at every level precision is required. Initially, a gear engineer must design a gear that meets the design intent while remaining cognizant of all variables that result from using materials such as plastic. This engineer must design a gear electrode that will actually determine the form of the gear. This electrode is then burned into the mold cavity using a method commonly referred to as EDM or electrical discharge machining. It is essential that the gear electrode be cut identical to the finished gear tooth form. Some compensation is normally made for the shrinkage of plastic as well as the overburn that occurs during the EDM process. The gear engineer normally will alter the gear tooth geometry to relieve stress and strengthen the gear tooth form. This alteration is normally done at the base or root of the gear tooth and at the tip or peak of the tooth. Next, a mold maker then will evaluate what the expected life of the gear program will be so that he can build a mold that is robust and capable producing the many millions of parts with the highest of accuracy. He will ensure that the plastic that will be entering the mold will travel along balanced pathway or runner system that will allow for consistent fill into each mold cavity. His tool for evaluating this flow is done through a computer model commonly referred to as mold flow analysis. He must be capable of understanding what makes a good mold as well as a good gear. Once the mold is completed it is then set into an injection-molding machine. It is important in the precision gear molding industry that the molding unit has a highly controlled system in place to monitor the molding process. It is equally important during this process that there is a means by which all peripheral variables can be controlled. This is done utilizing a central processor, which will maintain balance on all settings for every parameter. Transducers relay all of their information into a central processor that will monitor and maintain this consistent process.