JSP is a global business serving the automotive, construction, civil engineering and packaging markets with a range of expanded polymers. When the company first began to embed plastic and metal components into its automotive seat designs fabricated in ARPRO® expanded polypropylene (EPP), its engineers discovered that this made post-fabrication shrinkage of the product more difficult to predict. The modeling and simulation methods they were using at the time failed to account for thermal effects during shrinkage, making simulations of the manufacturing process unrevealing and unreliable. Consequently, additional physical trial and error were required to achieve the correct final form, stretching out development schedules and driving up costs.
To overcome that problem, JSP adopted ESI Group’s ESI Virtual Seat Solution (VSS). With this new technology, JSP engineers found they can now—reliably and recurrently—define a target shape that includes plastic and/or metal molded inserts, select the density of their ARPRO® foam, then calculate the mold shape that will deliver the required geometry for each component upon completion of the molding and curing process.
“ESI Virtual Seat Solution allowed JSP to accurately predict the distortion of parts as they cured,” says JSP engineering manager Kipp Boegner. “Consequently, we were able to design molds that compensated for that distortion before they were constructed, saving us a tremendous amount of time, effort and money. This improvement in JSP’s capabilities is a competitive advantage that we can use to capture additional business and increase our market share.”
EPP foam benefits for automotive seat fabrication
JSP is a global supplier of ARPRO® expanded polypropylene (EPP) foam, used in the manufacture of a wide range of automotive components. Because of its high strength-to-weight ratio, ARPRO is widely used in seating structures to achieve significant weight reduction. The material is also highly versatile, so seats can be readily engineered to control the H-point for different driver/passenger morphologies.
Metal wires can be molded directly into an ARPRO® part. These insert-molded components create integrated subassemblies that can be used as primary or secondary attachment features to the steel seat frame or for structural enhancements. The addition of these elements provides opportunity for further weight reductions as they can replace the traditional heavy, steel anti-submarine ramp.
A typically molded ARPRO® foam part, without insert-molded components, will typically shrink about 2% in volume after a standard molding process. However, the addition of plastic or metal components molded into the ARPRO® part cause the part shrinkage to vary locally, resulting in dimensional errors in the final molded part if these effects are not predicted and then factored into the mold shape.
How JSP used ESI VSS to fix the problem
To accurately predict shrinkage, JSP turned to ESI Virtual Seat Solution (VSS). JSP’s first objective was to check the methodology and predictive capability of ESI VSS regarding the final distorted shape of the ARPRO® foam parts after they are manufactured and cooled to ambient temperature. Then, with the help of VSS, they looked into predicting the compensations in mold shape that were required so that the desired product geometry would be achieved after cooling. Last, they wanted to output the predicted compensated mold geometry to a CAD file for mold construction.
Today, using ESI Virtual Seat Solution, JSP can input a targeted part shape, including insert-molded plastic and metal inserts, select the desired density of ARPRO® foam, then run a simulation to predict the corrected mold shape that will be necessary to achieve the targeted part shape after the molding and curing process.
To date, JSP has successfully completed and correlated more than 18 studies to validate ESI VSS’s capabilities. Satisfied with the results, JSP has commissioned and constructed five production-capable molds based on ESI VSS’s output. These first molds have produced dimensionally capable parts as predicted, with no significant costs for revision.