For some in the plastics injection moulding industry, attempting to maintain a constant temperature regime within what is essentially a cyclical production process means accepting compromised results. A number of engineering teams are working right now across Europe on technologies that use cyclical thermal regulation to improve the quality of demanding plastics mouldings.

The latest to demonstrate its capabilities is an engineering team at the Kunststoff Institut LŸdenscheid, which demonstrated its Indumold induction mould heating technique in production of a black ABS structural foam bottle opener at the Fakuma show last autumn.

Running on a Wittmann Battenfeld 110 tonne HM machine, the process was applied to one surface of the mould to yield a high gloss finish in place of the usual porous and swirled structural foam surface. The high gloss surface was achieved by keeping the mould surface close to the polymer melting point during filling to delay the onset of freezing, followed by rapid cooling of the filled mould cavity.

In the Indumold process, this is achieved through the use of induction heating coils integrated into the mould together with two separate conformal cooling circuits, which are positioned close to the mould cavity surface to achieve very fast response. During the filling stage, a high temperature water circuit maintained at 60C provides background control, while integrated induction heaters capable of lifting the temperature of the mould surface to 330C within six seconds provide almost instant additional heat input. Once the mould is filled, a second water cooling circuit maintained at 20C cools the part.

KIMW project partner Wittman Battenfeld says the high gloss foamed mouldings achieved using the Indumold technology provide higher rigidity and lower weight than compact alternatives and also eliminate visible knit lines. The traditional structural foam benefits of freedom from sink marks and warping in thick sections are maintained.