Controlled Foaming Creates Best of Two Worlds

In what seems like a pretty straightforward process, two German organizations are promoting a concept they call “pull and foam” in which foaming is controlled by

Cross section shows solid section at left and foamed area at right.

withdrawing a mold core at a certain point in the injection process.

That makes it possible to produce components that combine thin-walled foamed surfaces with stronger, unfoamed sections.

Foaming is attractive to reduce part weight and reduce part warpage. The new approach is based on the idea that the foaming process does not start until the cavity expands—after the injection of resin that is loaded with blowing agent and after the thin-walled areas of the component are solidified.

Reducing pressure in the enlarged cavity areas initializes the foaming, expanding the polymer melt. The foaming degree of the reinforcing ribs can be controlled by cavity enlargement. As a result, rib structures that are extremely lightweight but stable can be produced. The process creates:

  • Thin-walled, compact and optically high-quality areas with large- ribs;
  • Structures that are lightweight in specific areas; and
  • The ability to reduce clamping pressure.

The process is under development by 3 Pi Consulting & Management (Paderborn, Germany) and the Institute of Materials Engineering – Polymer Technology at the

Foaming agent goes to work (bottom) as core is pulled, expanding the cavity.

University of Kassel (Kassel, Germany).

They see several potential applications in the automotive industry, consumer electronic industry, furniture industry and medical engineering can be mentioned.

“There is no license or patent but we want to bring it into market by selling our knowhow,” says Dr. Joachim Schnieders (, who heads 3 Pi Consulting & Management. He says there are no commercial customers to date, but they are ready to launch the system.


About Doug Smock

Former Chief Editor at Plastics World and Senior Technical Editor Design News

Automotive, Blowing Agents, Construction, Consumer Goods, Design, Electronics, Europe, Gas-Assist Injection Molding, Industrial, Injection Molding, Office Products, Sports

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