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The latest in-mold technology: Hot gas welding from Engel

The latest in a long list of processing technologies from the Austria-based, globally operating injection molding and automation supplier Engel creates yet another acronym starting with IM for in-mold: Now there's "IMW" for in-mold welding.

PlasticsToday Staff

February 2, 2011

2 Min Read
The latest in-mold technology: Hot gas welding from Engel

Working with collaborators Hummel-Formen and KVT Bielefeld, Engel has a patent pending for what it has named joinmelt: hot gas welding inside the mold, which moves yet another traditional downstream, post-mold process back upstream into the tool.

The joinmelt technology, says Engel, promises considerable savings, especially in the automotive industry. "This removes the need for additional welding equipment. Part take-off and re-insertion are no longer needed, as the finished product can simply be taken off directly out of the mold." says Franz Füreder, head of Engel's Automotive Business Unit.

How joinmelt works is deceptively simple. Both halves of a component are injected simultaneously in a single mold. After cooling, the mold opens and one half of the final component remains in each half of the mold. The movable mold half is repositioned so the two halves of the final part are facing each other. A heating element is positioned between the cavities and heats the edges of the two halves of the component. The mold closes again, bonding the heated edges of the part halves. The mold reopens and the finished part, now effectively one piece, is removed.

Engel notes that the savings from integrating two manufacturing steps, most notably the reduced overall cycle time, are only the start of joinmelt's benefits. It also improves the quality and safe functionality of the part. There are no warpage issues since the product halves stay fixed in the mold until they are welded. And the weld is clean, thin, and particularly resistant to bursting pressure compared with previous joining techniques.

Engel says joinmelt is suitable for all thermoplastics. The developers of the process see high potential for glass fiber reinforced polyamide parts for automotive engine compartments. Such components, they say, have always had a visible bulge at the joint, which made them susceptible to friction and reduced the service life of nearby functional parts.

Eliminating the weld bulge also saves material and reduces finished part weight. Even product development is simplified: there is no need to work with a specific welding direction, which enables broader design freedom with part geometry.

Engel's joinmelt development partners
Hummel-Formen (Lenningen, Germany), which brought its moldmaking technology to the project, has a patent pending for hot gas welding in an injection mold. The 250-person toolmaker produces injection and compression molds weighing up to 100 tonnes in its two factories.

KVT Bielefeld (Bielefeld, Germany), which is responsible for joinmelt's welding technology, holds a patent for hot gas welding in a protected atmosphere to ensure a particle-free and very stable weld. Its welding systems are used by makers of autos and appliances as well as telecommunications and medical devices.

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