In 2019, 50-year-old UK-based Mitre Plastics manufactured a high-volume brass insert part for an appliance manufacturer. Mitre Plastics asked an automation supplier to create a concept design using its FANUC ROBOSHOT -S220iB injection moulding machine to identify the manufacturing process.
FANUC and Mitre Plastics worked together to create automated robotic merchandising for white goods. When FANUC engineers learned of Mitre’s first manufacturing plan, they underlined the limits of a cobot. In order to have more flexibility in performing activities such as removing gates, they suggested changing the current three-axis robot to a six-axis side-entry robot. Unlike the limited mobility of the three-axis robot, the six-axis robot allows full rotation and unrestricted movement.
According to general manager Michael Breckon, “They recommended that we use a collaborative robot in addition to our current injection moulding machine and the three-axis robot to handle the insert loading.”
But as Mitre Plastics was already a FANUC customer for injection moulding and trusted the company’s automation expertise, it chose to consult FANUC before making the cobot purchase.
Alternative strategy
According to Michael, when we presented the plan to FANUC to discuss the supply of additional hardware and the work involved in integrating the solution, questions arose about how it would work in practice.
FANUC engineers found that the proposed solution had several limitations and was not entirely suitable for a cobot, according to a review. James Pointer, senior integration engineer at FANUC.
Firstly, collaborative robots are designed to operate unattended, but in this case a guard was needed, which increased the cost.
Secondly, the idea required mounting the cobot at head height on the moulding machine, which is against health and safety regulations.
Thirdly, although cobots are slow by nature, the aim of injection moulding is to keep the mould as open as possible to optimise production.
FANUC proposed a six-axis robotic cell as a simpler, faster and more efficient solution. A six-axis side-entry robot was developed in collaboration with the company and Hi-Tech, a key FANUC partner. Within the allotted cycle time, this robot would accept four inserts from a bucket feeder, enter the moulding machine through a side door, place them in the proper position, demould the final component and perform post-moulding inspections.
FANUC designed a self-contained industrial automation cell to reduce cost and complexity. FANUC simulated the cell using ROBOGUIDE software and cycle time studies to determine the optimal robot model for the best price-performance ratio. The M-20iD/35 system, with a reach of 1.8 m and a payload of 35 kg, supports double-sided gripper and sensor actuation.
In this project, flexibility was essential, as the moulding machine had to adapt to various tasks. A six-axis robot was excellent because it could move freely and rotate completely. A three-axis robot can move along three axes, but a six-axis robot can move freely and rotate completely. This flexibility is essential for manufacturing plastic components with overmoulded inserts, as efficient production depends on accuracy and precision.
Mitre Plastics initially had reservations about its ability to operate the six-axis robot, fearing difficulties in programming and staff qualification. However, Dave Veal, technical director, reports that these doubts were unfounded. The programming software has evolved and the support from FANUC has been excellent. Mitre Plastics engineers now have a better solution and are beginning to see the benefits of six-axis technology.
Mitre Plastics has found a significant advantage in using a six-axis robot for gate removal. Previously, the three-axis robot performed the secondary operation of removing the gates with pneumatic cutting tools, but now offers the part to a single cutter, reducing costs and changeover time. The six-axis robot offers greater flexibility in removing the gates from products, making it more cost-effective and efficient.
The importance of continually developing capabilities through technology, such as pushing the moulding machine harder to produce parts to customer specifications and minimising labour requirements. The robot becomes central to the thinking around the machine, and the more sophisticated the robot, the more competitive it can be.
The new cost-effective technology gave Mitre Plastics the ability to use a six-axis robot and the option to reassign the three-axis robot to another activity.