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Situation:
Germany's largest non-club book dispatcher, the Weltbild publishing group, currently uses five robot cells with Epson SCARAs. The dispatching area features five labelling lines on which the articles are processed. The first article in the batch to be dispatched with the starter label is read-in with a hand scanner and placed manually on the conveyor belt. The server for the labelling lines compares the label data with the invoice data and transfers this data record to the labelling-station computer. It issues the print command to the label printer for all the labels relevant to that individual article. "In our old dispatch centre, labelling was the bottleneck," remembers the technical head of Weltbild. "We label the articles »according to type«, but books, CDs, software packages etc. are labelled in random order. All these articles have different dimensions. They range from playing card format to packing cartons 400 millimetres in height.
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Solution:
Project Manager Robert Block was responsible for the project from the outset: "For us, using a Scara for labelling seemed the logical solution owing to its size, speed and workspace geometry. Thanks to its design, the device requires little space and it only needs to perform point-to-point movements in the horizontal axis – from the label printer, where it picks up the label, to the article, which passes immediately in front of the robot on the conveyor belt. The height-differences of the various articles can also be ideally compensated by the Z-axis of the SCARA. The relevant data for this purpose is supplied by a 2-D laser measurement system above the conveyor belt, which measures the articles in three dimensions as they pass by. And this is the beauty of the robot solution. Regardless of the article processed by the robot – the control system automatically calculates the optimum acceleration ramps and the speeds of all four axes."
With a belt speed of approx. 0.8 metres per second, a maximum of 4000 labels can be affixed per hour. For this purpose, the SCARA is equipped with a special vacuum gripper on the Z-axis, by means of which it picks up label after label from the printer, placing them onto the relevant articles. The robot switches from »pick up label« to »place label« in milliseconds. Labelling throughput depends on the dimensions of the articles. But we have become significantly more efficient and ergonomic. Downtimes are a thing of the past.
Notes:
"We had decided on the robot solution for labelling and then had to integrate the robot cells with their controllers into a very complex facility control system. ... A great challenge was the interaction between the conveyor belt speed, label printing, label pick-up by the robot, vacuum control and the placing of the labels on the articles for dispatch. We wanted to achieve a cycle time of under one second, and in the end, we managed to do so. The facility was commissioned in the autumn of 1998, and has been running smoothly ever since."
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