Technicl Report
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Six-axis robot takes charge of grinding, drilling and de-burring

Why the engine factory Maschinenfabrik Reinhausen GmbH at Regensburg uses robot-aided manufacturing technologies.

With the globalization of production, a new competitive environment prevails making the deployment of robots in automation processes a necessity. Even the most ardent skeptics now admit that not only can robots work faster and cheaper than their human equivalents, but more importantly, can complete the job with a higher level of reproducible quality and safety. 14 years ago these advantage led to the deployment of robotic grinding systems at engineering factories Maschinenfabrik Reinhausen GmbH in Regensburg, switching from manual to robotic handling of various mechanical processing tasks, such as grinding, drilling and cutting. In fact, the Head of the CPM2 department stated: “We manufacture variable switches for power supply and over the years have developed a wide range of components and devices for power transmission, distribution and peripheral equipment. Since these are high-performance and high-power products, which have to meet specific stringent requirements over a long period of time, we have to consider the following criteria regarding the use of mechanical production techniques for the electrical contact, switching elements and housings: 1. Process safety and security; 2. Quality; 3. Productivity; and 4. The human element in the workplace.” Based on this manufacturing strategy, it has become clear that the ability to reproduce quality is of utmost importance. Consequently, at the end of the 80’s, the CPM department, which at that time was equipped with rather conventional systems, was restructured, and older processes and machinery were gradually replaced with state-of-the-art technologies and systems. By involving the employees in the early stages of these change processes, and by providing them with information, education and advanced training, the department was able to lay the groundwork to ensure the most rational manufacture of parts, often using unconventional techniques and investments that held the most promise of success.

In the mid-90s at the manufacturing department at CPM, the idea of deploying a robot for carrying out mechanical processing developed. This was like a small revolution back then. The Corporate Management – always open to new ideas in innovation in manufacturing processes – supported this future-oriented project. While searching for an appropriate supplier of robotic grinding and processing systems, CPM contacted SHL Automatisierungstechnik AG in Böttingen. To start with, the company conducted training sessions and performed specialized tests. In 1988, they placed an order for the first of three almost identical robotic grinding and processing systems. As Mr. Franz Kleber said: “Right from the beginning, we did not consider the robots to be a replacement for the workers for the grinding contact parts, switching elements and other parts made of copper, but looked upon them more as multi-functional machines for different processing tasks. That is what the robot can do, the grinding machines were also available, and with additional spindles it was possible to introduce the use of other tools, such as those required for milling, drilling and cutting. Although we had envisioned the robotic grinding system for grinding contact elements made of copper, we also wanted to use it for other processing tasks and utilize it to its fullest capacity in shift operation. In close cooperation with the application specialists at SHL, we were then able to create a multi-functional and universally applicable robotic processing system, which we presently use to grind parts made of copper and aluminum, de-burr sheet metal parts, drill and cut and also polish the sheet metal parts”. 

Universal robotic processing center

The SHL robotic grinding systems for this purpose have been conceived as completely encapsulated processing cells, each consisting primarily of one 6-axis industrial robot, KUKA KR 30/3, for a maximum load capacity of 30 Kg., one double contact wheel grinding machine, a PDKS that can be positioned, rotary table / turntable, dual-brush machine, DDP550 ROB, milling spindles, rotary clamping unit to turn and enclose work-pieces, replaceable clamp for different work-piece grippers, dual feed table for unfinished parts in pallets, conveyor for removing the finished work-pieces, sound-proof cabin (booth) with ventilation ducts, and safety equipment and controller with software and a handheld operator terminal.

The dual-brush machine and both the milling spindles were installed on the rotary table, turntable and depending on the processing task, can automatically swivel into the working position. The dual or pallet shuttle table positions the parts in the pallets or fixtures in the right position for the robot. The robot picks one part, moves it to the respective processing station for grinding (copper and aluminum parts) or for de-burring, drilling and cutting (sheet metal parts, sheet metal housings) and places it on the discharge conveyor belt after processing it. The conveyor is long enough to use as a buffer for completing the desired number of parts. The operator must manually pick the copper and aluminum parts that have been ground and place them in a fine grinding and polishing station to carry out the finishing work. The sheet metal parts are removed and placed in a transport container. Based on the main processing task – namely grinding and brushing contact-point parts and switching elements made of copper and aluminum – the two pallets of the feed system can hold 2 x 60 = 120 parts. Around 100 pieces are produced per shift, which means that 300 pieces are manufactured when operating three shifts a day. Consequently, the plant runs completely automatically beyond one shift, and the operator can dedicate himself to the finishing work (1 minute per piece), programming the robot, and controlling the material flow and handling activities.

State-of-the-art Manufacturing Technology” 

Based on the successful experience with the robotic grinding and processing system from SHL, CPM procured two other systems in 2002 and 2006, so that the mechanical production department (CPM 2) now has three identical robotic cells. Those in charge of the CPM parts manufacturing department were unanimous in their praise: “We have done pioneering work here and are now using state-of-the-art manufacturing technology. However, this has not been achieved as a hands off operation, but, instead, on the basis of pure conviction that automation and dedicated employees make up a powerful unit only when the employees fully accept the technology. At our company, we have parts with long life cycles, and we had to repeatedly make thousands of precise boreholes and cuts on sheet metal parts. The idea of using a robot to do these tasks instead of doing them manually quickly crystallized. Consequently, the rotary and swivel unit with the dual-brush machine and the two milling/drilling/cutting spindles made their mark and we now process these sheet metal parts automatically, up to 600 parts per shift. To process such a sheet metal part – which can include drilling, cutting, milling and de-burring – we used to need six times as much time, and now we deliver the part readymade by the system. Upgrading or retrofitting the system gets done quickly since we equipped the system in such a manner that all assemblies and tools are already available and only the grippers, part holders and the processing programs need to be changed or updated.Since we use the robotic grinding and processing systems in a highly universal and flexible manner, we can, to a large extent, amortize the costs and ensure the return on investment. At present, we have a substantial lead in robot-aided processing technology and, at the same time, have also contributed to the economy and humanization of the workplace.”