PET preform molders can achieve a big jump in productivity without having to invest in special machines with rotating platens. Now there’s a way to raise the output of a conventional injection press by up to 50%. The answer is a patented shuttling mold system developed by Tooling Preform Systems b.v. (TPS) of the Netherlands, whose U.S. representative is PET Solutions, Inc., Winsted, Conn.
The shuttle mold contains twice as many mold cores as cavities. Between the cavities are cooling cells. After half the cores have been injected on one cycle, the core half of the mold shuttles to the left or right so that the fresh preforms mate with the cooling cells. Those preforms complete their cooling while a new set of preforms is injected. Because of the extra cooling time, the initial molding cycle can be reduced by 33%.
TPS has built shuttle molds with 32 and 48 cavities. The same approach has been used to speed molding of larger parts, like salad bowls.
The shuttling mold half slides on roller bearings and is powered by servo-controlled hydraulic cylinders. Shuttle stroke is about 4 in. and takes 0.8 sec. The width of the mold is extended just enough to accommodate one extra row of cooling cells. As the shuttle mold is essentially a “mold and a half,” tool cost is increased by around 50%, TPS says.