A high level of process integration and complete automation are the decisive factors to achieve the required efficiency in manufacturing fuse boxes for agricultural utility vehicles. The production equipment is flexible due to its modularity. The plastics processor REINERT describes the recently completed project as a milestone and praises the excellent teamwork with its partner companies MAIER and WITTMANN.
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The W832 pro robot from WITTMANN is the link between injection molding and downstream processing steps |
In terms of technology expertise, REINERT is certainly ahead of the game. With its focus on the automotive industry, the plastics processor can offer a remarkable range of services, including multi-component injection molding, as well as gas injection, various insert molding techniques, clean-room production and even organo sheet processing to make light-weight parts. “We are also often in demand as development partner, especially when the task is tricky”, explains Jürgen Hahn, Managing Director of REINERT Kunststofftechnik GmbH & Co. KG, during our visit to the company’s headquarters in Bissingen an der Teck, Germany – and the component lying in front of us on the table in the large conference room is certainly rather complex.
It is a fuse box for agricultural utility vehicles, consisting of two black boxes clipped together with sealing, numerous sockets and screws, plus lateral red brackets to hold the cover in place after electrical installation. “Both boxes have come out of the injection molding machine as complete assemblies including sealing and metal inserts, except for the red brackets”, Christoph Klement, Deputy Project Manager at REINERT, explains proudly. “This project is really a milestone for our company.”
18 variants and other products in quick succession
The challenge in this project was more than just the high cost pressure, which has long been quite common in the automotive sector, but rather the necessity to combine lowest possible unit costs with extremely high flexibility of the production cell. In fact, the fuse boxes from REINERT are produced in 18 different variants. Moreover, it was necessary to enable the highly automated production cell to be fully utilized by making some other products as well.
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During the pre-series phase, the inserts are still being fed manually. But everything has been prepared for using vibrating bowls, hoppers and separators |
“That is the trend”; emphasizes Alen Cevra, Managing Director of MAIER Maschinen- und Werkzeugbau GmbH, which is in charge of developing the integrated production process and the automation involved. “Especially here in Germany, we are more and more often dealing with a wide range of different products and consequently small batch sizes. This requires fast and simple machine setting processes, as well as the necessary flexibility for frequent readjustment of the production cell’s components to new requirements.”
With its headquarters in Markgröningen, Germany, and another facility in the immediate neighborhood of REINERT in Bissingen, MAIER specializes in the design and production of complex customized machinery and automation solutions. MAIER has already supported the injection molding processor REINERT for many years in developing production equipment for extremely complex parts. “Mr. Klement came to us with a CAD drawing of the part”, says Cevra. That was in the early summer of 2022. Less than one year later, the fully automated production cell had already been delivered. This success was the result of excellent teamwork between all participating companies. “The key factor is communication. We can discuss everything openly, even in the event of occasional differences of opinion, and we all know that we can rely on each other”, emphasizes Andreas Schramm, Managing Director of WITTMANN BATTENFELD Deutschland GmbH, the third partner in the project. WITTMANN delivered a large W832 pro linear robot, which handles the inserts as well as the finished parts and thus functions as the link between the injection molding process and the subsequent processing steps.
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The process starts with arranging the inserts
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A linear robot mastering many different tasks
In spite of extensive automation, the production process now starts with manual work while the project is still at the pre-series stage. The inserts must be sorted into exchangeable trays. There are three types of inserts, which are required in different numbers for each fuse box model. Accordingly, there are three different exchangeable trays which are placed into a drawer after being filled, and are then passed on into the production cell. At that point, the robots take over. First, a small six-axis robot chips in, whose task is to arrange the sockets and screws required for one fuse box in the specified grid dimensions. The WITTMANN W832 pro takes up the inserts and places them into the lower cavity of the rotary mold inside the injection molding machine. Immediately afterwards, the gripper removes out of the top cavity the finished molded part from the previous cycle. In the 1+1-cavity mold, the base body is formed first. The hard component is a fiberglass-reinforced, flame-retardant polyamide. After rotating the mold, the second component, a TPE material, is directly molded on to provide the seal for the upper edge of the fuse box. Simultaneously, the next base element is formed inside the lower part of the mold.
Parallel to the injection molding process, the W832 pro also performs an assembly task plus a thorough quality check. From the injection molding machine, the robot first takes the part to the assembly station. In the base of the black fuse box model running off the clock-out belt on the day of our visit, there are four small holes. Later on – when installed in the vehicle – these will provide ventilation. They are now covered with a silicone membrane. To this end, the robot holds the box horizontally above the assembly station, thus enabling the rising stamp to fit the seal onto it accurately.
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The WITTMANN robot operates with different grippers to provide flexible support for 18 product variants |
For the 100 per cent quality check, MAIER has installed a camera system right next to the assembly station. The robot must move the part only 20 centimeters to the right. Here, the W832 pro robot’s rotary servo axes play out their strengths, for they are required to present in quick succession three different critical points on the molded part to the camera. First comes the silicone membrane just mounted. It is checked whether the membrane has been fitted correctly and whether the holes below it – each only 1 mm in diameter – are all open. At this point, the LED camera installed on the gripper comes on in order to take perfect pictures for evaluation. After checking the ventilation valve, the robot turns the part to give the camera a clear view onto the TPE seal. The camera focuses precisely on the part of the seal which penetrates most deeply into the hard component. “If this part is completely filled, the rest of the seal is also faultless”, says Fabio D’Amato, COO of MAIER. Finally, the connector coding is checked. If the image processing system signals OK three times, the W832 pro then deposits the fuse box on the clock-out belt and immediately picks up a new set of inserts for the next cycle.
Real-time communication across corporate boundaries
To enable an extremely fast changeover from one fuse box model to another, there are not 18 different molds, but instead several different mold inserts and grippers. A particularly large amount of coordination work has been invested in the grippers. Where to place the valves? How to guide the energy chain so that the end-of-arm tooling can turn the part in the shortest possible time? And how to save weight? The WITTMANN team had really looked into every detail and fully exploited all efficiency potentials.
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Inside the rotary mold, Polyamide and TPE are processed simultaneously |
The lighter the robot arm, the more scope is available for the weight of the gripper and the parts to be moved. What is more, light weight has a direct positive effect on energy efficiency – a topic particularly close to the heart of the decision-makers at REINERT. They are pleased to find the WITTMANN linear robot equipped with a sustainable feature. Thanks to EcoMode, the robot varies the speed of its movements. The injection molding machine sets the clock with its cycle time. The robot fully utilizes this time window, which means that most of the time it moves more slowly than technically feasible. This saves energy and simultaneously protects the mechanism in the interest of a long service life for the robot.
To provide communication between all components of the production cell – including the injection molding machine, the two robots, the assembly station and the image processing system, all coming from different manufacturers and each equipped with their own control systems – they are interconnected via Profinet. This industrial Ethernet standard laid out for real-time communication ensures a smooth process and facilitates the production startup following machine setting. Before the central control unit of the automation cell starts the production process, it checks whether the correct program has been set on the injection molding machine and on the linear robot. The network system also enables fast remote servicing in the event of a malfunction. The specialist engineers from MAIER can access the cell from outside, to check the control system of all individual components and to view the camera images from quality assurance. “WITTMANN is the ideal integration partner”, says D’Amato. “Not all robots offer so much flexibility and openness.”
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The camera for the fully automatic 100 per cent quality check is installed between the assembly station and the clock-out belt |
Easy operation is vital
WITTMANN was already well known to REINERT long before the fuse box project got under way. Many more WITTMANN robots are operating on the production floor in Bissingen, and products from WITTMANN are also in use at the two other plants of REINERT in Czechia and Romania.
“Our production staff members are top fit as well as familiar with programming and operating the robots from WITTMANN”, says Klement. “This is mainly due to the easy operation and continuity in operating logic across many generations of robots.”
At the beginning of the project, an articulated robot for the tasks of insertion, removal, assembly and quality checks was briefly considered.
But REINERT deliberately decided against this option. “I have always said that things should be kept as simple as possible”, explains Jürgen Hahn. “That minimizes the error risk, and our machine operators are very keen and highly motivated.” The Managing Director is also familiar with the further advantages of WITTMANN: “The robots are sturdy and long-lasting; we are getting excellent service. “
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Jointly exploiting all efficiency potentials: Alen Cevra from MAIER, Andreas Schramm from WITTMANN BATTENFELD Deutschland, machine operators Robil Gün, Christoph Klement and Jürgen Hahn from REINERT, and Fabio D’Amato from MAIER (from left to right) |
Geared for growth
In close teamwork, REINERT, MAIER and WITTMANN have trimmed the automation of the entire process for maximum efficiency and flexibility. Every detail was analyzed in order to meet all requirements and still keep the costs reasonable. Programmers and software experts from WITTMANN were also on board. “Whenever something has to be re-programmed, it took just a telephone call, and the work could go on at once”, says D’Amato.
The production cell is laid out to produce up to 400,000 assemblies per year. In the pre-series, 50,000 fuse boxes for agricultural utility vehicles are being produced to begin with. How fast the numbers of units may increase is not foreseeable. For a start, the production cell is to be fully utilized with other, equally complex parts. “The basic concept of the production cell keeps all options open for us”, says Christoph Klement. As soon as the fuse boxes really take off, the trays now being filled manually can very easily be replaced by vibrating bowls, hoppers and separators. Then the equipment will be able to maintain autonomous production for up to eight hours.
Photos: WITTMANN
