How a Lean Robot Strategy Revolutionized Automotive Overmolding Production

KHG Plastics GmbH’s newest addition to its Velberg, Germany facility is a pair of compact vertical injection‑molding cells. Together, they can produce roughly 40,000 overmolded electrical contacts each week for automotive lighting systems, seamlessly integrating metal fabrication, overmolding, testing and packaging into a fully automated process—executed with remarkable elegance and simplicity.

Initially, KHG Plastics planned to shuttle parts through the various stages with two six‑axis robots, a human operator and supplementary automation. Sepro, in partnership with local integrator Kiki, presented a streamlined alternative: three linear, three‑axis robots coordinated by a single control system. The result was a more compact, higher‑producing cell—demonstrating how unconventional solutions can yield superior outcomes.

Automating Multiple Functions

After securing the opportunity to produce a new overmolded metal contact for an automaker’s vehicle lighting systems, KHG set out to design a fully automated production line that would weave together a range of equipment:

 • a metal‑punching and bending machine to process blanks into left‑ and right‑oriented contacts;  • a vertical injection‑molding machine to overmold the metal stampings;  • a test station for 500 V short‑circuit verification;  • a packaging station that transfers “good” parts into stackable trays for downstream automation or shipment.

Because the workflow involved pre‑ and post‑mold operations, the initial concept called for two six‑axis robots—one large, centrally‑located unit to handle stamping, molding, and testing, and a smaller robot to load finished parts into trays. Though logical, this layout raised concerns about footprint and reach. Sepro’s Marius Svagnea promptly confirmed that a linear robot could replace the large six‑axis unit. The Sepro S5‑35, a three‑axis model, offered a 4000 mm horizontal stroke, drastically reducing cell size and providing easier access for maintenance and equipment changes.

Building on this insight, Svagnea suggested a second linear robot, the smaller Success 7, to take over handling of tested parts, and a third, the Success 11, to manage tray loading, unloading, and stacking. Positioning the linear robots above the molding machines simplified machinery placement, lowered floor‑space requirements, and maintained full reach thanks to customizable horizontal beams.

KHG was impressed: "We saw that a six‑axis robot would have taken too much space and had too limited a reach," said CEO Lutz Karrenberg. "The Sepro/Kiki solution combined several standard robots in a very small space. This was the main reason behind our decision."

Karrenberg added, "We did not necessarily at first think of a solution with a tray cart that would include loading via a third robot system. This idea came completely from Sepro, who had already implemented something of a similar nature. This solution not only saved us a lot of space, but also optimized our workflow and brought a high flexibility to the system for future production tasks."

Cells in Operation

Each robot operates under its own Sepro Visual controller, but the Visual 3 on the S5‑35 also serves as the master controller, synchronizing safety and operations across the cell.

The S5‑35 begins the cycle by picking up four stamped and bent contacts—two left‑hand and two right‑hand—from the punching and bending unit’s shuttle table. It then places them into the lower half of the vertical injection‑molding machine’s open turntable, secures them with end‑of‑arm tooling, and initiates overmolding. After removing the previous cycle’s four finished parts, the robot transfers the new parts to the test station, where a 500 V short‑circuit test is performed. Acceptable parts are then moved to a transfer station; rejected parts are removed from the line.

Next, the Success 7 extracts tested parts from the transfer station, sorts them by orientation, and deposits them into the appropriate part tray. With a 1500 mm horizontal stroke, it efficiently handles this task.

Finally, the Success 11 manages tray logistics: it moves filled trays to unloading stations, stacks them onto movable carts, retrieves empty trays from storage, and places them back onto the sliding table for the next filling cycle.

The only human intervention required is the removal of full trays—approximately every six hours.

Simplifying Multi‑Machine Integration

Coordinating three robots and a suite of metalworking, injection‑molding, electrical testing, and tray‑handling equipment would normally demand separate PLCs and extensive custom programming. Sepro’s Visual 3 control, augmented by the Easy Package feature set, integrated all key equipment seamlessly. Easy Package extends Euromap 67’s injection press/robot interoperability and adds synchronization, control, monitoring, and data‑exchange capabilities across E79 and E81 protocols.

“The ease of integration is the big advantage of Sepro’s portfolio,” said KHG’s Lutz Karrenberg. By leveraging Sepro’s integration tools through trusted partners, KHG achieved two production cells that deliver more elegant, powerful, and cost‑efficient results than the initially considered, more complex systems—while requiring less programming and integration effort. Moreover, the design facilitates rapid redeployment of assets when future production needs evolve.