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ROBOTICS SIX-AXIS SIMPLICITY
Automation expertise from FANUC has supported injection moulding firm Mitre Plastics to specify a flexible six-axis robot cell during its latest project for a white goods manufacturer. After first considering a cobot solution, Mitre Plastics has instead, with FANUC’s help, commissioned a faster, more cost- effective, and more flexible industrial robot system, helping the company to fulfil its contract with a major customer.
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ocated in north-east England and boasting a 50-year history, in 2019, Mitre Plastics was invited to quote for producing a high-volume part with a brass insert for a white goods manufacturer, requiring a
repeatable, high-speed insert loading solution. To get an idea of how the part could be produced on its existing FANUC ROBOSHOT
α-S220iB injection moulding machine, Mitre Plastics asked an unnamed automation
supplier to scope out a conceptual solution. “They suggested using a collaborative robot in conjunction with our existing injection moulding machine and three-axis robot to handle insert loading,” recalls general manager Michael Breckon. However, as an existing FANUC injection moulding customer and therefore confident in the company’s automation knowledge and expertise, Mitre Plastics decided to seek FANUC’s advice before committing to the cobot purchase.
AN ALTERNATIVE APPROACH “When we took the proposal to FANUC to discuss providing additional hardware and integration work for the solution, it raised questions over how it would work in practice,” says Breckon.
The review highlighted a number of limitations with the proposed solution, with FANUC’s engineers concluding that this application was not wholly suited to a cobot. FANUC’s senior integration engineer James Pointer explains why: “Firstly, collaborative robots are intended to work unguarded, but in this case, a guard was required, adding cost. Secondly, the proposal was to mount the cobot on the moulding machine at head
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height, which would not comply with health & safety guidelines. And thirdly, cobots are inherently slow, whereas the key with injection moulding is to minimise mould open time for maximum productivity.”
A SEAMLESS PARTNERSHIP Instead of a cobot, FANUC proposed a simpler, faster, more efficient and more flexible solution, comprising a six-axis robot cell. To assist in this alternative approach, it engaged Hi-Tech, its long-term strategic partner for injection moulding handling and integration. The two companies worked seamlessly to devise a solution that involved replacing the existing three-axis robot with a side-entry six- axis robot. This would take four inserts from a bowl feeder, enter the moulding machine through the side door, place the inserts into the mould in the correct orientation, demould the finished component and conduct post-mould checks – all within the specified cycle time. “With the aim of reducing cost and complexity to the existing
system, we designed a self-contained industrial
automation cell,” says Pointer. With all parties happy with this concept, FANUC then simulated the cell on its proprietary ROBOGUIDE software and completed cycle time studies to determine the optimum robot model for the best price:performance ratio over the system’s lifetime. “ROBOGUIDE allows us to investigate how different specifications can influence life cycle. These simulations told us we needed a 1.8m reach and a 35kg payload to accommodate the actuation and sensors needed for a double-sided gripper, which led us to the M- 20iD/35,” says Pointer.
The M-20iD/35 six-axis robot gives full rotation and free movement which is invaluable for a manufacture of plastic parts with over moulded inserts giving precision and accuracy.
FLEXIBILITY FOREMOST
Flexibility was also an important consideration in this project as, although the contract was large, other work still needed to be kept on the moulding machine. This made a six-axis robot ideal, as Pointer explains: “As the name suggests, with a three-axis robot you have three axes of movement: up and down, left and right, forwards and backwards, so when the gripper comes down you can’t change the angle. A six-axis, in comparison, gives you full rotation and therefore free movement. For the manufacture of plastic parts with over moulded inserts, this freedom of movement is invaluable, as precision and accuracy are key to successful production.”
MORALE BOOST
While the new proposal seemed ideal, one problem with a change in approach at this stage was that the original cobot solution had already received capex approval. However, this concern was soon assuaged when the new system came in at a similar cost, as well as giving Mitre Plastics six-axis robot capability and the option of re-tasking the three-axis robot elsewhere in the factory. Hurdles overcome, the cell was installed just before Christmas 2021, ready for production start-up in mid-2022. “This was a long-term investment that supports the company’s ongoing commitment to technical development. It also demonstrated our commitment to the customer and gave them
Autumn 2023 UKManufacturing
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