New approach to fast, uniform mold cooling

Variety may be the spice of life, but in plastics processing — where the key to survival is the production of uniform parts — it’s invariably an unwelcome ingredient.

As too many plastics manufacturers have discovered, variations in a mold’s surface temperature during the molding process can cause serious problems: part distortion, mold condensation and corrosion, and increased mold maintenance and downtime, to name just a few of the most costly and time-consuming.

Now, however, Toronto-based distributor SWM & Associates has introduced the RiTemp mold cooling technology to the North American market, which promises to help eliminate these troublesome mold “hot spots”, as well as speed molding cycles.

Developed by RiTemp Technology Pty. Ltd., of Edwardstown, South Australia, the RiTemp technology replaces conventional gun-drilled water channels — which can cause uneven cooling in the mold, and thus part warping — with large cooling chambers that provide uniform mold temperatures regardless of part geometry.

Machined out of the core and cavity sides of the mold, each chamber contains a predetermined amount of water. Air is evacuated from the chamber, allowing water to boil at low temperatures (50 Fahrenheit) — an important point, the company said, because the change from liquid to gas removes more heat than simply heating liquid water. The flow of the water, or coolant, is controlled by a mold temperature control that senses and adjusts flow to regulate heat levels. With cooling applied only where it is needed in the mold, a high degree of uniformity is achieved.

And since oxygen is not allowed into the cooling process chambers, the likelihood of corrosion, or sweating, on the mold is significantly reduced.

According to Scott Molnar, president of SWM & Associates, the RiTemp technology is well suited to any process in which there is a delay for part curing. “The physics of RiTemp applies across the board to all applications, from injection molding to blow molding,” he said. “Our experience to date is with lower cavitation systems, but we are rapidly moving to higher cavitation, for example a new 32-cavity mold, as well as stack molding and automotive applications.” The process can be used with all types of resins, Molnar added.

Premiered for the North American market in June, at the National Plastics Exhibition (NPE) 2006 in Chicago, SWM & Associates has begun issuing case studies that illustrate the success of the RiTemp process. The first release detailed the manufacture of a 15 gram electrical box with a 1.5 mm critical wall thickness dimension. The cycle time for this application had been 18 seconds on a two-cavity production mold; using the RiTemp technology in the design and manufacture of a new four-cavity production tool to run the identical part resulted in the cycle time being cut to 13 seconds. To date, the RiTemp mold has produced seven million parts without fail, Molnar added.

Molnar believes that, given the erosion in margins and the number of North American businesses that are moving offshore, the time has arrived for the RiTemp technology. “RiTemp demonstrates clearly how, in real applications terms, North American companies can leverage technology and maintain a healthy margin,” he said. “If we can help one company stay in business, then RiTemp has done its job.”

SWM & Associates (Toronto, Ont.);

www.swm-associates.com; 416-786-2663