Venting injection molds is complex. Especially with fiberglass-reinforced and flame-retardant materials, additional gases can enter the mold through the material. This leads to defect patterns that result in scrap or require additional mold optimization. The SKZ Plastics Center is now working on a joint project to develop solutions for specific applications through simulation and extensive practical testing.
Burner at the end of the flow path of a fiber-reinforced component - fiber-reinforced thermoplastics in particular have a tendency to increased "gas formation". (Photo: SKZ)
Venting injection molds has always been a complex problem that has not been solved satisfactorily. When polymer is injected into the cavity, it displaces more than just the air trapped inside. Many thermoplastics form gaseous products that also enter the mold. These include fiber-reinforced and/or flame-retardant materials. But venting problems can also occur with polyolefins, polycarbonates and polyamides.
Generating measurement data in the field
Today, there are a number of possible solutions for tool venting. Examples include porous structures, crevices, relief grinding and many more. What is often missing, however, is the knowledge of which of these methods is best suited for a specific case in order to avoid errors or additional iteration loops. For this reason, the experts at SKZ are now offering interested companies the opportunity to take part in a joint pioneering project to generate measurement data through practical trials and to develop a simulation model that incorporates venting concepts and thus helps to find efficient solutions in tool design.
Optimization Potential in Industry
"Simulation programs can already make predictions about sensible venting positions. However, there is often a discrepancy between this and reality, or the filling behavior changes as a result of the implemented venting, so that the vent position also 'shifts'," says Christian Deubel, Senior Engineer at SKZ. How much gas is then vented through a particular vent during the injection phase depends on its performance and design. Especially with venting gaps, the rule is usually: "As little as possible, as much as necessary. However, there is still potential for optimization in the industry. "That is why we decided to start the project," Deubel continues.
Exclusivity of Results in Pathfinder Projects
The special feature of SKZ Pathfinder projects is the even stronger focus on industrial application and the exclusivity of the results, since these projects are financed exclusively by the participating companies and are only available to them. Through the acquisition of test data and objective trials, SKZ researchers hope to be able to use rheological injection molding simulations and a real-world vent evaluation test rig to significantly improve the prediction of critical or venting areas and determine a vent with optimal performance in the right location. At the end of the trailblazer project, participants will have a literature review of venting solutions and concrete recommendations for action.