When Simmatic was approached by motion control specialist CR Solutions with a request to develop a vacuum pick-up head for a robot-based pick-and-place machine, the application sounded straightforward. The head, mounted on the end of the robot arm, simply had to pick up five small boxes at a time from an infeed conveyor and then, after the arm had moved to the appropriate location, deposit them within a shipping carton. As is so often the case, however, the devil was in the detail, and Simmatic had to overcome multiple challenges on the way to devising a successful solution.
The pick-and-place machine was required to handle different box sizes with varying heights. All the boxes were small – no more than 100mm per side – and light in weight. The boxes were shrink-wrapped but, because of the fragile contents, a tight shrink wrap could not be used. This meant that the wrap film had seams and tended to form bubbles, which made it more difficult to lift the boxes reliably.
A key requirement was that the pick-up head, complete with its associated vacuum generator, had to be small enough to fit inside the shipping carton. The head also had to be designed so that the boxes could be placed right into the corners of the deep shipping carton, and there had to be no risk that the head would damage the carton.
Simmatic carried out extensive trials with sample boxes to devise the most convenient, reliable and cost-effective solution. The use of a sponge lifting pad was soon ruled out because it could not be relied upon to provide a consistently good seal with the somewhat irregular surface of the shrink-wrapped boxes.
The Simmatic engineers therefore trialled a 80 × 500mm lifting head, fitted with 21 lifting cups arranged in three rows of seven. Each cup was 15mm in diameter, and was fitted with long bellows to help accommodate the varying height and irregular surface of the boxes. The head was equipped with a multistage vacuum generator, powered by compressed air. This compact device helped to satisfy the requirement for a head that would fit within the shipping carton and, since it has no moving parts, offered the additional benefit of being maintenance-free.
While this prototype head worked well in most respects, it was not able to position the boxes right into the corners of the shipping cartons. To solve this problem, Simmatic developed a slightly smaller head measuring 80 × 335mm, which was fitted with the same arrangement of lifting cups as the prototype.
Secure lift and transport
The use of multiple cups was a big benefit in this application as, even if some of the cups were not fully covered when lifting boxes of a particular size, or the irregularities in the shrink film made it impossible for some cups to achieve a good seal, the remaining cups would still maintain good vacuum, ensuring that the boxes were lifted and transported securely.
A further benefit was that this arrangement allowed boxes that extended beyond the edge of the head to be lifted securely, which made it much easier to accurately place them along the edges and into the corners of the shipping carton.
The pick-and-place machine, with its robot systems supplied and programmed by CR Solutions allied with the customised pick-up head devised by Simmatic, has now be extensively tested with every size of box it is required to handle. It has delivered faultless performance, with no dropped boxes, no permanent deformation of the shrink-wrap film and no damage to the shipping carton.
As anticipated, the head’s integrated vacuum generator works efficiently and almost silently. Since it has a fast response time and is located close to the pick-up cups, it needs to be switched on only when boxes are being lifted and transported. This means that it is much more energy efficient than the alternative of an external motor driven vacuum pump which would need to run continuously.
Shaun Corkish, Senior Controls Engineer at CR Solutions says: “This was undoubtedly one of those projects that initially looks simple but is actually not. Many aspects of the job were challenging, and one of the biggest challenges was reliably lifting the product boxes without damaging them. Simmatic did a great job in helping us to achieve this, and provided excellent responsive support at every stage of the project. Simmatic proved to be an ideal partner for the project with genuine in-depth expertise and an outstanding product range.”
For more information please visit www.simmatic.co.uk.