REDUCED-VOLUME SCREWS EXPANDED ARTICLE, PLASTICS WORLD - MARCH, 1994

When you are forced to use a large press to mold a small shot size, for example, running a 20 oz. shot on a 50 oz. press, you have the potential for material degradation due to the long residence time. The risk varies, of course, with the specifics of the job and type of plastic. Process control may also be an issue. The usual solution to this small-shot problem is to downsize, or retrofit the machine with a smaller bore barrel, mating screw, tip assembly, end cap, and drive adapter. Thus, a one of a kind injection unit is created. This type of modification increases injection pressure, which must also be dealt with. Unless the screw and barrel are shortened, the length to diameter ratio will be increased. As a result, this solution is very expensive and time consuming to install when compared to Concor's procedure.