As a result of three-way German collaboration, it is now possible to perform hot gas welding directly in an injection mold.
In the innovative process called “joinmelt”, both halves of a component are injected simultaneously into a single mold. After the cooling phase, the mold is opened with one half of the part remaining in the left half and the other in the right half of the mold. The movable left half of the mold is then positioned so that both parts are opposite each other in welding position. A heating element is positioned between the cavities and the edges of the component halves are heated. When the mold closes, the two parts are bonded so that the finished part can be taken off when the mold re-opens.
“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. Collaborating with Engel are mold specialist Hummel-Formen and welding specialist KVT Bielefeld. A patent application has been filed.
The partners see huge potential in processing of glass fiber reinforced polyamides (nylons) as bearing parts for under the hood (UTH). Thus far these components have always had a visible bulge at the joint, making them prone to friction and reducing the service life of other functional parts, such as the valve tappets. The “joinmelt” process avoids the bulge, the saving material and weight. It’s also good news for design engineers. There is no need to account for a specific welding technique, allowing more creative part geometry.