Pre-impregnation composite materials – or pre-preg composites as they’re usually known – typically take the form of heavy, floppy sheets that resemble the thick felt used for roofing purposes. Their flexibility and weight means that pre-preg composites are notoriously difficult to handle. When a pattern maker asked Simmatic to devise a reliable way of lifting pre-preg sheets into an autoclave for curing, however, our application experts knew that vacuum handling was the way to go. He also knew that choosing exactly the right type of lifting cup would be critical for success.
We assessed the requirements carefully and decided that a cup that had pliable lips would be the best choice for handling the flexible sheets. There was, however, a further complication. When the sheets are stacked ready for transfer to the oven, the top of the stack is often tilted a little, which means that the pick-up system needs to be tolerant of angular misalignment.
Drawing on the exceptional number of cup options available in the VMECA range, we selected a soft-lipped 80 mm Smart Suction Cup. These cups incorporate a “smart plunger” comprising ball joint and levelling spring, which means that they automatically compensate for angular misalignment up to ± 21º. They are also self-centring, so that even if successive sheets of composite are presented to them at different angles, they can still pick them up without difficulty.
Trials confirmed that the soft lips of the cup followed the contour of the product well, allowing a good vacuum seal to be achieved. In addition, the smart plunger easily dealt with the non-uniform presentation of the composite sheets. In service, the handling system devised, manufactured and supplied by Simmatic has proved to be extremely reliable.
There is, however, a sequel to this tale! A Simmatic competitor offered to provide the end customer with a second system for essentially the same application, but at a lower price than that offered by Simmatic.
When installed, this low-cost system could not be made to work – success depends on the unique properties of the VMECA Smart Cups. These cost a little more than generic cups but have a wider angular compliance than any other product of their type. Once again, however, Simmatic came to the rescue by rebuilding and retrofitting the failed system and putting it into full working order in less than two weeks.