Molding and Sealing Integrated in a Single Cell

Due to the introduction of the Mold’n Seal process, developed by Sonderhoff, the Swiss company Weidplas, working in the automotive industry, was able to increase production efficiency, reducing at the same time the equipment footprint. In fact, the injection molding and the low-emission plyurethane FERMAPOR® K31gasket sealing immediately afterwards of a component for the passenger compartment have been integrated in a single cell.

by Sebastiano Mainarda

The automotive supplier and injection molding specialist Weidplas aimed at maximizing process efficiency of the entire parts production, minimizing rejects and thus reducing production costs.
This could be achieved by the process integration of various production steps: the injection molding of the parts and the sealing immediately afterwards in one cell.
The solution was the Mold’n Seal, developed by Sonderhoff, now part of Henkel, which runs as series production at the Weidplas plant in Rüti, Switzerland. The injection molding machine, unloading unit and six-axis robot for injection molding have been supplied by Engel.
Sonderhoff supplied the mixing and dosing system DM 402 with the precision mixing head MK 625, in the process version Mold’n Seal, which provides for a machine configuration that combines the processes of injection molding with the immediate subsequent sealing of the components in an inline production.

Flexible dispensing system
Plastic components and their seals must not emit pollutants such as volatile organic compounds (VOCs), even at extreme temperatures, such as those often prevalent in direct sunlight during summer. They can cause a health hazard beyond a certain amount. In this specific case, the target value for the VOC emission is set at 100 μg/g of polyurethane.
The Mold’n Seal system, developed by Sonderhoff, provides customers with a cost and time-saving integration solution for injection molding and gasketing in the smallest of spaces. The DM 402 dispensing system used at Mold’n Seal can be flexibly adjusted to the customer’s specific production situation, the design of the component to be foamed, and the property profile of the seal formulation.
By combining the injection molding system with the mixing and dosing system, Weidplas can save space, time, energy and costs. As a result, higher production output is possible with lower unit costs.

The work cycle of the Mold’n Seal cell
More into details, the Mold’n Seal process integration is based on an injection molding plant, a picking robot and a six-axis robot from Engel, as well as a mixing and dosing system DM402 with mixing head MK 625 and the mixing head traversing unit, which is moved electrically, provided by Sonderhoff. The advantage, in this case, is a freely programmable stop positions on the movement path, instead of pneumatically with fixed stop positions.
The plant periphery consists of an automatic refill station that pumps the A component of the FERMAPOR® K31 low-emission foam gasket and the B component into the respective pressure vessels of the dispensing system; plasma nozzles for activation of the component surfaces for improved adhesion of the foam seal; a cooling and curing section and a conveyor belt and a temperature control unit.
Due to the high reactivity of the fast-reacting low-emission foam system, the material pipes must be cooled leading to the mixing head.
The components are produced by Weidplas using a 2-cavity mold by injection molding. The supply of the components to the Mold’n Seal manufacturing cell has been designed such as that a refilling of the parts buffer takes place at reasonable time intervals.
After injection molding with the Engel system, the tool opens and the removal robot removes two components from the cavities (Figure 2) and moves them to the conveyor belt.
The remaining component is positioned at a plasma nozzle for plasma activation of the component bottom side. After the plasma pretreatment, the removal robot places the component for further processing (Figure 3), moves to the injection molding unit again, waits there until the tool opens and withdraws two parts again.
At the same time, the 6-axis robot grips the component deposited at the storage/exchange fixture with the plasma-activated underside and moves to the mixing head MK 625 of the dispensing system DM 402 from Sonderhoff. There it positions the component under the mixing head nozzle for foaming the plasma-activated side (Figure 4).
The mixing head MK 625 of the Mold’n Seal system from Sonderhoff precisely meters the low-emission seal foam into the groove of the component (Figure 5).

Traceability and control are guaranteed
The six-axis robot then moves the part with the foaming side facing upwards to the plasma nozzle to activate the unblended side with plasma. He then drives back to the mixing head to apply the second side with low-emission sealing foam. The same robot then places the finished foamed component on the cooling and curing section and removes a new part from the storage/exchange unit.
According to Weidplas management, one big challenge was certainly that the component has a seal on both sides and the surface must first be activated before the foam is applied.
Thanks to a simple and continuous operating concept, the Mold’n Seal system at Weidplas can be operated safely and ergonomically. Active functions and states are signaled by the illuminated buttons. Selectable functions/states are signaled by the flashing of the buttons.
All malfunctions, process parameters and their changes are documented by the Mold’n Seal system and can therefore be traced at any time.
But the last control at Weidplas is the machine operator of the Mold’n Seal plant, which checks the quality of component processing.

The role of plyurethane foam gasketing
The Sonderhoff Mold’n Seal process involves the inline processing of injection-molded components followed by direct application of a polyurethane seal in accordance with the FIPFG (Formed In-Place Foam Gasket) sealing technology. Injection molding and dispensing equipment as well as handling robots are placed in a very compact production cell.
For Sonderhoff, the challenge for the use of the Mold’n Seal process at Weidplas was to design the formulation for the low-emission foam so that the foaming process to form a foam gasket would be adapted to the injection molding cycle.
With the fast-cure foam seals FERMAPOR® K31 the component application could be successfully implemented within the injection molding cycle. After 2-3 minutes at room temperature, the surface of the foam seal is tack-free and the foamed components can be processed quickly. By integrating the processes of injection molding and foam gasketing, it is possible to save considerable time in the entire production process at Weidplas.
Thanks to the high level of process engineering expertise and the many years of expertise of all the companies involved in the project, the compatibility of the challenging material properties, coupled with a modular and compact system concept, has been successfully implemented in a high-wage location such as Switzerland.