COOL FLOW SYSTEM – Hot cycle using cool gas injection technology

In 2001, Stieler Kunststoff Service GmbH developed the gas cooling technology which within a couple of months entered serial production. Today, the equipments can be found in serial productions world-wide (Czech Republic, Hungary, Brazil, USA, China, England, Spain, and Germany).

Gas injection is a special process in the field of plastics injection molding.
A gas, in most cases it is nitrogen, is injected into the plastic to create hollows in a well-directed way. These hollows even out the stress inside the plastic product and they also reduce its weight. Depending on the process, the holding pressure of the gas can reduce the cycle. With some products, however, a gas channel emerges that can not be “skived” properly by the gas. This is because the differing flow speeds result in mass concentrations. These mass concentrations make the cycle longer. After-shrinkage has dramatic consequences: the product deforms and can no longer be considered true to size. It is exactly this point that our technology starts at: Cold gas with the COOL FLOW SYSTEM.


Because compressing the gas produces heat, the gas can only be cooled effectively under high pressure. At about 350 bar, the nitrogen is cooled down to a temperature of about - 25°C. The cooled nitrogen is fed to the specially modified control valves and gas nozzles and is then slowly flushed through the product’s hollow.

The gas injection process is first performed conventionally. Only when the volumetric shrinkage of the plastic is nearly complete (after about 5 - 10 seconds), a specially designed venting pin is fed into the void. Under counter-pressure, the cold gas is then flushed through the hollow.

The cycle of the products, which had been mass-produced since 2001, was reduced between 25 % and 40 %. The product is also much truer to size, because the demolding temperature of the mass concentrations is similar to the demolding temperature of the wall area. With PP, for example, the demolding temperature was reduced from 110°C to less than 70°C; at the same time, the cycle time was also significantly reduced.

coolflow_polo   Door lining, VW Polo
40 % reduction in cycle time
5 mm reduction in shape distortion


At the beginning of the technical development, some already completed molds were redesigned at great expense. By now, some adept mold-makers produce molds that are specially designed for the COOL FLOW SYSTEM.

Stieler Kunststoff Service GmbH distributes and licenses the self-developed COOL FLOW SYSTEM exclusively with Stieler controllers and high-pressure cooling devices from the company Beko Technologies. Stieler has installed the applications containing the COOL FLOW SYSTEM for a serial production in locations all over the world; these include among others the Czech Republic, Hungary, Brazil, Spain, China, England, the USA, and of course Germany.

compact-150-x-279    beko-blizz-201-x-200

350 bar high-pressure cooling device (- 25°C) with a specially modified controller