New cell streamlines foaming within injection molding

Inline foaming is a chore no more. A new fully automatic production cell from Arburg and sealing systems supplier Sonderhoff interlinks injection molding with seal foaming to save time and costs for producing parts like auto headlamp housing covers.

In convention applications, the foaming process is kept separate from the actual molding process, making it a classic downstream process step; pre-produced parts are kept in storage and then transferred to the foaming system at a later point by means of conveyor belts.

Arburg and Sonderhoff’s new “mold’n’seal” cell uses a hydraulic Allrounder 570 S injection molding machine with a clamping force of 2,200 kN from Arburg and a four-cavity mold, in a three-step production process. First, glass fibre-reinforced polypropylene (PP 35 GF) car headlamp housing covers, including the sealing groove, are first molded; each part weighs 68 grams, and the cycle time for injection molding, handling and foaming the four components is 44 seconds. Second, a single Kuka six-axis robot with a Selogica control system performs all the handling tasks and links the injection molding with the subsequent seal foaming process; the robotic system simultaneously removes the four still-warm molded parts and immediately transfers them inline to the Sonderhoff DM 402/403 mixing and dosage unit, placing each housing successively under the mixing head. Finally, FIPFG (formed-in-place foam gasket) technology is used to produce a soft elastic polyurethane (PUR) foam seal that’s foamed precisely to the contours. While the PUR bead is dosed by means of the fixed MK 600 mixing head, the Kuka six-axis robotic system moves along the freely programmable contour geometry, which is adapted to the groove of the plastic part. Its so-called “circ and spline” movements ensure that the foam is applied very evenly and precisely at a constant speed, even along complex grooves with tight curves.

The work cell offers a checklist of benefits: The residual heat of the molded parts further accelerates the curing of the PUR foam, reducing the overall curing time from north to 10 minutes to less than three; there’s no need for buffered or pre-produced injection molded parts, which also doing away with expensive interim storage; long curing or conveyor belts are no longer necessary; the designed-for-Dummies (our term, not theirs) Selogica control system removes the need for special programming expertise; and at approximately 50 square metres, the space requirement for injection molding machine, robotic system, dosage unit and curing belt is low.

To watch a video of the cell in action, click on this link: http://www.youtube.com/watch?v=SCmjuW5W8Ak