Plastic Molding Machinery
Injection Molding Machines and Selection Resin
Injection molding machines are manufactured in many sizes. There are rated according to size by the amount of material which can be injection in one cycle, ranging from a fration of an ounce in the samll laboratory models to many pounds in large production equipement. Laboratory models are used in the rearch and development of new polymers and molding techniques.
There are two basic unit of an injection molding machine; one for injecting the heated plastic and other for opening and closing the plastic mold. The first unit includes a feed hopper, heated injection cylinder, and an injection plunger or screw system. The second unit comprises a hydraulic operated moving platen and a stationary platen on which the halves of the mold are mounted. Injection molding machineare also available in vertical models.
There are many variations in injection molding machine design, however, the basic machines are of either the screw-ram, of plunger type. The main differences between these types is the method in which the plastic material is delivered from the hopper to the nozzle of the machine. Machine of the reciprocating-screw type are used more because of faster cycles, lower melting temperaturers, and better mixing of the material.
The injection molding machine has a variety of instrumentation used for the clamping unit, mold, and injection mollding machine shows the most important possibilities of the instrumentation. In fact, there is no known direct method for in-line checking of the condition of the mold.