More and more companies are turning to robotics to reduce operating costs. One such company is cable management specialist, C&C Marshall Ltd. The company has installed two TM Robotics’ SR-554 HSP SCARA robots at one of its UK plastics molding plants. The installation was prompted by the need to reduce the man-hours spent on the shop floor and increase production.
Before the investment in robotics was made, the now automated functions were performed manually. However, this was inefficient and generated problems of its own, including repetitive strain injury. “Often manufacturers who have never worked with robotics, discover unexpected benefits when they do,” said Nigel Smith, managing director of TM Robotics, Shibaura Machine’s UK sales partner. “Avoiding costly compensation claims for RSI is one of these. The more tangible benefits are production increases and the ability to function on a genuine 24/7 basis.”
TM Robotics’ SR-554 HSP robots were selected over five-axis systems because they offer greater speed, improved accuracy and far more attractive prices. In one application the SCARA robots work in conjunction with a plastics moulding machine and a Star Automation Cartesian robot.
The SCARA positions swivel clamps in dry lining boxes, for use in electrical installations. When installed, the box sits between the socket plate and the wall. It contains the switchgear needed to operate the socket, keeping the system insulated.
When automating the application, the plastics moulding company approached Star Automation, which, in turn, involved Evershed Robotics, a specialist integrator. It was at this point that the decision was made to use Shibaura Machine's SCARA SR-554 to compliment Star Automation’s Cartesian robot.
The process uses the Cartesian robot to move four dry lining boxes from the moulding machine into inserting nests, where the swivel clamp is inserted. The Shibaura Machine robot is bowl-fed with the clamps and places each one in the correct position in those mouldings or boxes. The Cartesian robot then pick ups the boxes and drops them onto a carrier before they are placed onto a packing carousal.
The gap, into which the clamps are inserted, is less than 5mm wide. The repeatability of the TM Robotics SCARA is therefore vital. When choosing such a robot the distinction between accuracy and repeatability is of major importance. Accuracy applies to just one movement. Repeatability ensures the accurate movement is repeated on every occasion.
In addition to this process, the entire system can be called upon to produce a dozen product variations, of which two thirds are versions of the dry lining box. Of these, the system described is the most complex.
The Shibaura Machine SCARA robot is controlled via the Cartesian robot and receives all of its signals from here. However, the SCARA is also provided with a teach pendant and an SR7000 robot controller as an interface. Either of these can be employed, should manual programming or shutdown become necessary. The system has four binary data channels, which digitally transmit information to the SCARA. The SCARA acknowledges receipt of the programme from the Cartesian robot before actioning it. There is a separate programme for each of the products that the system builds.
In a similar robot application, running at the same plant, the robot program is loaded via the teach pendant. In this application, a shuttle system places tiny inserts on holders. A Star Automation Cartesian robot picks up the inserts and places them in the moulding machine. The box is then moulded around the inserts. In this application, the speed of the SCARA robot is the key feature. It has to place the inserts onto each of 16 holders within a 34 second cycle time. Again, Evershed Robotics integrated this application.
Both applications operate a traffic light system to manage the human intervention required. Under this system a blue light signifies that the inserts need to be replenished. A red light means a manual stop is required.
Operating on its most common program, the system shifts 10,000 dry lining boxes a day. Before automation, the clamps were manually inserted into the boxes. Just three people now operate the entire SCARA system. Previously eight people were required. Given that five to six tons of boxes are produced per week, this represents a significant improvement on the factory’s bottom line.
“Our client sells half a million dry lining boxes a year,” said Les Clarke, managing director of Evershed Robotics Limited. “The company sells predominantly through specialist electrical wholesalers, although it also works with a number of specialist departments in larger companies. These include architects, building contractors and the like. Automating the process means that it can now offer a more reliable and profitable service to its customers.”
“The typical payback on a SCARA is eighteen months, but this system paid for itself in six. Obviously, the smaller the run, the longer the payback time,” said Clarke. “When we chose the Shibaura Machine robot, reach and ease of programming were the key factors. Having said that, the solution we chose still only uses ten percent of the robots capacity.”
In light of this experience, why don’t all manufacturing companies immediately turn to robotics to improve their plants? On this subject, engineers are ahead of the game. They already understand that automation of existing processes can increase a plant’s output and reduce its overheads. They recognise that more efficient work practices can be just as effective, in terms of the bottom line, as simply increasing production.
“The reluctance with employing automation lies not with the plant engineers, but in the boardroom,” said Smith. “Financial directors often know little of engineering. Thus, it is understandable that these people might believe that an extra injection-moulding machine might be the best way of improving productivity. However, as we have demonstrated, this isn’t always true. An improved process can be even more valuable.”