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Task
Automation of the production of a handle for a Bosch angle grinder using a FANUC ROBOSHOT and FANUC Robot.

Solution
The cell was planned and implemented in-house by Hans Arnold GmbH. FANUC contributed the know-how for the parameterisation of the interface between ROBOSHOT and robot. 

The structure of the cell is quickly described: the all-electric ROBOSHOT α-S150iA injection moulding machine and an M-20iA robot from FANUC, feed technology from Grimm with separation technology for screws, vision system from FANUC with Sony camera enclosed by a protective fence.

The handles are moulded in a four-cavity mould, are hollow on the inside and have a receptacle for an insert. A robot removes the plastic handles at a demoulding temperature of 80 to 90°C and fills one plastic part at a time with an insert screw. It then moves to the press-fitting station, where the metal screws are pressed into the still soft plastic so that exactly 12 mm of the thread protrudes on the screw-on side. All four screws are pressed in at the same time. The finished handles are then subjected to two visual inspection processes and finally placed in a wire mesh box.

Result
All processes are initiated and controlled via the robot controller. The system was deliberately built without a PLC. When switched on, it is set to the initial state by a reference run of the robot and can be started from the injection moulding machine. The robot is partially integrated into the ROBOSHOT via FANUC's own I/O Link interface, making it easy to control even for inexperienced operators.

Produits FANUC utilisés

The automation of plastics machines is one thing: it costs money, which has to be added to the price of the parts. The market for injection moulded parts is also highly competitive - every tenth of a cent counts. So other criteria have to be decisive for automation.

The decision to do so was made long ago at Hans Arnold Kunststofftechnik, Mühlhausen, meanwhile also for complex tasks and production sections.

The company, which was founded a good 40 years ago, now has about 170 employees, including a joint venture in Hungary. Petra Arnold-Herpertz, a graduate in industrial engineering, manages the company together with her father and founder Hans Arnold: "We are in the process of making the company fit for the future. That's why we are automating, not least out of our own interest." 
The criteria are not at all sector- or company-specific. Wage costs are not decreasing, skilled personnel is not available at will and the quality demands of customers are increasing. Initial experiences have manifested themselves in the realisation: When the process is up and running, I get 100 % quality directly from the machine. Especially in injection moulding processes with inserts, there is no way around the use of robots for the experienced automation specialist, as production manager Kevin Lützkendorf says: "Manual insertion is prone to errors and I can cover complicated processes better with a robot. In addition, manual insertion tends to tie up staff in three shifts. In the meantime, Hans Arnold even goes so far as to insist on automation for quality reasons when a customer enquiries.
The automated future has already begun at Hans Arnold Kunststofftechnik with the production of the handle for a Bosch angle grinder.

The special feature: The cell was planned and realised in-house, on the one hand for cost reasons and on the other hand because the company expected a quick implementation from the in-house construction. To cut a long story short: Both goals were achieved.

The production of the predecessor handle provided the starting point. The tool was getting on in years and the design of the handle needed to be renewed. Together with the customer Bosch, Hans Arnold Kunststofftechnik then implemented the new handle and its production. To ensure that the handle fits well in the hand, it has a highly structured surface, which again was a challenge for the toolmaker. Kevin Lützkendorf: "We have our own toolmaker with many years of experience. For the Bosch handle, toolmaker Foboha from Haslach supported us." They had already built the tool for an older 2K variant of the handle. "That's why we wanted to stay with the familiar quality."
Four handles are moulded in a four-cavity mould, each of which is hollow on the inside and closed on the screw-on side. A robot removes the plastic handles at a demoulding temperature of 80 to 90°C and places them in sleeves in the press-fit station. The robot then positions one screw in each hollow handle, which is then pressed downwards through the still soft plastic so that exactly 12 mm of the thread protrudes on the screw-on side. All four screws are pressed together at the same time. The finished handles are then subjected to two test procedures, after which they are discarded.

The setup of the cell is quickly described: the all-electric ROBOSHOT α-S150iA injection moulding machine and an M-20iA robot from FANUC, feed technology from Grimm with separation technology for screws, vision system from FANUC with Sony camera enclosed by a protective fence.
"We didn't look at an existing construction kit, but concentrated on the plant," says Lützkendorf. "The system was ready in the first run. There was no correction loop." The project team also made use of the FANUC ROBOGUIDE software, which can be used to simulate the plant design in advance. As the design was done entirely in-house, all 3D data was available, which of course facilitated offline programming and simulation of the cell. This meant that all the data for the removal cycles and pressing could be transferred 1:1 into the programming. The corner points were set, the basic position and reference marks were laid out with ROBOGUIDE - and that was it. Only the actual removal process was fine-tuned on the machine.

All processes are initiated and controlled via the robot controller. The system was deliberately built without a PLC. When switched on, the robot makes a reference run, everything is set to the initial state and the system can be started from the injection moulding machine. "Via the I/O link interface, we have a perfect connection between the robot and the ROBOSHOT," says the production manager - including the peripherals such as the control of pneumatic valves, the screw feed or the pressing device. "It's all kept user-friendly and is also simple because the central components come from FANUC as a single source." In fact, the system is operated via a single button.
A process visualisation system was subsequently installed. Since the cell is located in an "unmanned" hall, it should always be possible to have a look at the status of the cell from the existing production hall. 

What was originally intended as a tool to display production data for the management has in practice developed into a real support for the employees. On the one hand, a glance at the status monitor saves unnecessary trips to the adjacent hall, and on the other hand, it immediately signals whether assistance is required. 
Standard systems and mechanisms are integrated into the cell for quality assurance. In the process itself, a sensor system monitors whether the screws are correctly seated after the pressing process and whether the required 12 mm thread protrudes from the plastic handle. In addition, a 100% visual inspection of the handles is carried out with a vision system from FANUC. Then the robot places each of the four handles evenly in the grid box.

The robot cycles upwards in steps of a few millimetres so that the parts fall a maximum of 10 mm high. Damage to the polyamide handles is virtually impossible. At the beginning of the production process, the robot senses the bottom and then layers 135 layers upwards at five depositing positions. The grid box holds 2,600 components - the production quantity of one shift. 

The cell runs from Monday morning to Saturday morning, or one shift longer depending on the order situation. Screws have to be refilled every three or four hours. Otherwise, the cell runs self-sufficiently. According to Kevin Lützkendorf, there is no question of "tuning measures": "Of course we still have a bit of breathing space in the process. But I don't have to produce more parts than I need." He is more concerned with utilising the machine evenly: "It is better to have a plannable, constant process than the shortest cycle times, which could endanger process reliability. That's no good in the end."

A ROBOSHOT α-S150i is in use in a loaded version with 180 tonnes clamping force and a larger mould opening. Daniel Armbruster, plastics expert at FANUC: "Here we have two interesting alternatives. The 150 t version is ideal for continuous production with high volumes and short cycle times. The 180 t version offers more flexibility, provided the cycle time is not the first selection criterion." 

Demoulding is done with an index tool. This means that the parts do not fall down during ejection, but are removed by the robot. Therefore, the drive-up distance of the machine is important in order to get into the mould well with the four-cavity gripper.

Fully electric ROBOSHOT injection moulding machines have been used at Hans Arnold Kunststofftechnik for more than a decade and they now fill almost half of the machine park. Petra Arnold-Herpertz, managing director of the company together with her father, pursues a consistent strategy: "For us, it is important to break new ground in terms of technical equipment as well and to signal to our customers our capability and willingness to perform." The main arguments in favour of the ROBOSHOT, she says, are its precision and energy efficiency. "Both criteria are important." For production manager Kevin Lützkendorf, maintenance and service is also an issue: 

"Recently we serviced our oldest ROBOSHOT, a 50 t machine purchased in 2007. There was nothing, nothing at all. The machine is still in impeccable condition, actually unchanged. If I hadn't insisted on preventive maintenance, the machine would probably continue to run for another ten years without any problems." Was there really nothing at all? A little grease had accumulated and a fan had been replaced - as a precaution. Otherwise, low-maintenance and service-friendly, no comparison to hydraulic machines.

Such experiences inspire, also with regard to the cooperation: "FANUC shines when it comes to advice, support and service," Lützkendorf praises his supplier. Daniel Armbruster, his contact person at FANUC, returns: "In our application support, we also let ourselves be completely involved with the customer, although with Arnold we also had discussion partners with precise ideas and an eye for the big picture."

The next project is already in the design phase. Lützkendorf: "For the new project, we will again do everything ourselves. This has the advantage that we don't have any friction losses in the coordination of the individual areas." Together with the customer, the decision was made in favour of automation. Now, Hans Arnold is still responsible for such a project and the activities are focussed on the company's own production. Petra Arnold-Herpertz is quite comfortable with the idea of realising projects outside the company with a "Hans Arnold Systemtechnik": "We believe that we can offer automated cells in the current constellation at such a favourable price that it is also interesting for other plastics manufacturers who want to implement automation with a smaller budget."

Lützkendorf: "We are not talking about systems with 20 robots. We're talking about a total package from the idea to the falling plastic part." However, until that happens, "we're still practising a bit," laughs the boss.