Robot-based plastic injection moulding

When Jörg Vetter drives up to the industrial park in Pforzheim in southern Germany, he gazes up at the building’s windows. “I enjoy watching it in operation every time.” The cell bringing a smile to the face of the Technical Manager at the injection moulding company Hermann Hauff GmbH & Co. KG is an Arburg Allrounder Cube 2900 injection moulding machine. Since 2019, it has been producing rollers for the upper baskets of dishwashers at Hauff. These plastic elements consist of two interconnected parts, a freely movable wheel and a fixed bushing. The rollers, which are essential for easy loading and unloading of dishwashers, are moulded in the injection moulding machine. Moulding and assembly take place here in a fully automated process that Hauff set up jointly with injection moulding machine manufacturer Arburg.

The task was to redesign the production and assembly of the rollers for upper baskets of dishwashers with the aim of achieving greater quantities and high efficiency while at the same time making optimal use of the limited production space. Arburg made this possible with the integrated Reverse Cube from Foboha. “It was about breaking with manual operations and setting up autonomous production from the injection moulding machine to the pallet – and doing this in a one-piece flow – in other words as a continuous, uninterrupted process,” explains robomotion Managing Director Andreas Wolf. Together with Jörg Vetter and his team, Arburg scrutinized the entire process in order to develop a system integrating the injection moulding machine and the Cube from Foboha, the associated robot cells as well as the required grippers and, together with robomotion, the palletizer.

“The development of the complete system took more than two years; the software alone accounting for one year,” reports Jörg Vetter. “It was a matter of constantly weighing things up and reconsidering them.” To meet Hauff’s specific requirements, Foboha configured the “Cube” – a tool uniting the production of two components with their assembly. The name “Reverse Cube 2900” of the injection moulding machines says it all. The steel cube can be counter-rotated about its central axis in the reverse direction, enabling the parts moulded here to be assembled in two work steps with the aid of a special gripper before being transported via a conveyor belt to the packaging and palletizing cell. “This is unique in the world and can only be found at our company,” Vetter states proudly.

To be able to introduce this complex production step into an ongoing manufacturing operation, it is essential to plan as precisely as possible. This is why Arburg und robomotion integrated KUKA.Sim – a smart planning software package for offline programming of KUKA robots – into the system development. “Precisely because the space in the production hall is so limited, it was important to try out the system and its functionalities before actually realizing them. For example, we were able to perform a cycle time analysis as early as the engineering phase and include it in the layout and design. It was 'learning by doing' in a virtual space,” Wolf says. “Without KUKA.Sim, the system configuration would certainly have been much more time-consuming and costly – or perhaps even have gone wrong. Particularly for a medium-sized company, that is just not an option.”

The accompanying in-depth understanding of the Cube system and its possibilities helps Jörg Vetter to get Hauff’s employees excited about the automation. “There is always a bit of convincing required to show that the new technology is not directed against people, but serves them and makes their work easier and more varied,” the technical manager explains. He also notes that this is a particularly important factor in times with an increasing shortage of skilled workers. “We are always optimizing. I’m already thinking a few steps ahead and am in consultation with our management and our technology partners as to how we can produce as many products as possible on one machine. If we see new opportunities that pay off, we will take advantage of them.”