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Fixture design using Expert Holding die cast parts with Alufix Automobile suppliers in Switzerland are on the ball and have developed into an important economic factor. Numerous companies manufacture interior parts for well-known vehicle manufacturers. One of those is Weidmann Plastics Technology AG, based in idyllic surroundings in Rapperswil, directly on Zurich lake. This Swiss company specializes in manufacturing die-cast parts. Their manufacturing spectrum ranges from passenger car battery covers to shower heads. Before new parts go into series manufacturing, they are dimensionally checked in the Measurement Engineering Department. While up until some years ago measurement predominantly took place in two dimensions, nowadays demands are substantially higher, so that extensive 3D-Measuring is often required. In order to be able to measure plastic parts in a defined position, special fixtures are necessary. These were provided in the past by a tooling department and waiting periods of more than a week were not unusual. In order to avoid such delay and at the same time relieve the busy tooling department they decided to change to a modular fixturing system. The staff in Weidmann’s Measurement Engineering Dept. build their own individual fixtures independently as and when they need them. Peter Gilgen, 3-D measuring specialist, has been working with the modular system Alufix from Witte, Bleckede for five years. "Once you understand the system, assembly is very easy," he explained, "set up is only limited to availability of our Alufix components. Since we work more and more with Alufix, we want to increase our range of items. The good thing is that the basic principle of the system never changes. That means any new parts always fit on our eight year old components." A substantial advantage of the system is that the components are reusable again and again. Since all fixtures are documented, it is no problem to dismantle and later on rebuild a fixture accurately. Thus the existing Alufix material is not tied up for long periods of time and can be used for other jobs. The Measurement Engineering team basically works using two different measuring concepts. "On the one hand we have individual fixtures, dedicated to a specific part. On the other hand we have complex fixtures which have to be pre-set on a measuring machine. Adjustment takes place on particular points specified by the customer. It is important that the fixtures are set up in such a way that they offer optimal access to measuring points and that the work piece is securely held. Mostly we are measuring free-form surfaces, in accuracy ranges of 6-7/100ths. "Plastic parts require special treatment. The material is often soft and the parts are unstable; distortion is the main problem. That means in order to gather accurate part data, the work pieces must not be clamped but only held in position. No pressure may be exerted on parts otherwise temporary deformation would result in incorrect measuring data", Mathias Schoppe, manager responsible for measuring at Weidmann Plastics Technology, explained In order to optimize fixture building further, Weidmann has recently started using Expert Design Software. Alufix Expert is a PC programme for automatic fixture building on screen. It enables fast and simple implementation of complex fixture projects allowing users to simulate different types of supports on screen. Part data, supplied by the customer is entered into the software. According to data entered different types of set up are shown and can be changed on screen, allowing the user to simulate the best possible configuration for the job. Subsequently, fixture design occurs taking previously defined support points into account. Beforehand a list of Alufix components that the customer has is entered into the software so that during design only existing elements available are incorporated. One project, for example for the BMW Group, comprised of up to 12 different work pieces. If each of these fixtures had gone to the tooling department to be manufactured it would have meant considerably more organisational and economical expenditure for the completion of the entire project. The possibility of building fixtures using Alufix Expert substantially speeded up actual fixture set up . In contrast to “on the spot” fixture building, which can involve a lot of trial and error, it was only necessary to set up according to the design.Using Expert makes it considerably easier to to design a fixture according to the measuring points requested by a customer. Measuring of parts is usually just prior to start of series manufacture, just at the time when design changes are sometimes made. “Fortunately Alufix modular fixturing system gives us the flexibility to change fixtures accordingly.”
Alufix system: Alufix is a modular fixturing system made out of high-tensile aluminium for assembling measuring fixtures, checking gauges, assembly or welding fixtures, cubes, gauges …..Additionally it is used in prototype departments, for stereo lithography and design developments. This modular system for holding work pieces is available in six sizes. The individual system sizes can be combined with each other. After use fixtures are disassembled and all single components can be reused to build new fixtures. Advantages of Alufix system High precision due to accurate machining of single items Very lightweight – but very stableSystem sizes are combinable No weight or size restrictions on work piecesFixtures are repeatable Components are reusableAfter disassembly small storage space required Parts library in CADDesign softwareLargely corrosion resistantHard-wearing and maintenance-free

Alufix Expert Alufix Expert is a PC-Programm for automated fixture design. Complex fixture projects are implemented faster and easier. Different support situations are simulated on screen. Alufix Expert is comprised of 2 programme modules called Styler and Builder. Entries are made by the user under Styler to define a fixture with regard to design, grid, frame type and contact point positions. The Builder takes that information and uses it to calculate a result which is portrayed on screen as a fixture. Designs developed by Alufix Expert can be transferred to AutoCAD and CATIA for further processing.
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