The easiest way to increase the flexibility and productivity of machine tools is to reduce setting-up times and downtime. A mechanical interface is an effective aid to achieving this. Doing the setting-up operations away from the machine gives quick job changes and ensures absolute positioning accuracy when changing between machines.
The GPS 240 pallet system is such an interface. It was originally developed for one-off manufacturing and short runs in mould tool production, but is increasingly used nowadays for precision machining in the manufacturing industry. The obvious reason is the ever shorter runs and the increased number of setting-up operations, causing downtime and poor utilisation of the resources offered by the highly capable machine tools of today. More and more users are realising the advantages of GPS 240 – reduced setting-up times, increased productivity and greater profitability.
Bühler Group supplies production systems and technical solutions for the foodstuffs industry, the chemical process industry and for pressure die-casting. The company operates internationally, with large production plants in Switzerland and Germany.
The group’s main plant in Uzwil, Switzerland, is responsible for producing the parts needed for in-house machine manufacturing. This includes metal-cutting machining of small cubic parts. Urs Wagner, in charge of this production line, explains that planning for more than 3200 parts can be quite problematic. The orders for one to 400 parts – although most runs are between four and ten parts – must be produced as economically as possible, and in the shortest possible time. The machining time per part varies between 20 minutes and 12 hours. Far too often, the setting-up was taking longer than the actual machining.
Effective interface. Three chucks are permanently mounted on the table of the multi-operation machine. Simpler parts are fixed directly to stops in the palletised vices. Complex parts are set up in palletised fixtures away from the machine.
Seven years ago, Bühler started to look for a solution that would reduce the ever-growing gap between part variation and setting-up time. They found it in GPS 240, which, with its robust design and powerful, accurate coupling, offered the stability essential for milling and boring.
The 0.002 mm accuracy of the system even exceeded Uzwil’s requirements. A crucial factor in the system’s favour was that it was equally suitable for machining steel and light alloy, and for wet or dry machining. Since most of the workpieces machined here are “vice parts”, two Mazak multi-operation machines were each fitted with three chucks. The vices are mounted on pallets, with the fixed jaw as the zero-point stop. With this interface, machining could start as soon as the machining program was loaded.
“We have now been working three shifts with the GPS 240 for almost seven years, with no problems”, says Urs Wagner, and continues: “We have definitely achieved our goals. By setting up away from the machine, while machining is going on, we’ve greatly reduced the throughput time. And possibly just as important – we can now respond quickly and flexibly to urgent jobs.”
“Since we have such widely differing workpieces, it’s difficult to express the advantages of GPS 240 in clear figures. But the throughput times per part and the cost picture speak for themselves. The fact is that we were on the point of farming out some of our production to meet our commitments. But the new interface created large production reserves which we can now exploit for subcontractor jobs, and this has improved our cost situation even more.”
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