Samenvatting

Nowadays, a lot of precision components are manufactured and have to be measured to check dimensions and geometry. Xpress PE started to develop a coordinate measuring machine with a sub-micron measuring uncertainty called TriNano. The difference between the TriNano and other machines is that the TriNano saves up to 75% of capital investment of the customer. In this thesis project a workpiece holder for the TriNano is developed. The workpiece holder makes easy placement of workpieces in the small TriNano machine and machining centres possible. The two most important function are the "positioning" and "clamping" of the holder.
Positioning of the workpiece holder in the TriNano is done using the three V-groove coupling. This coupling is kinematic determined in six degrees of freedom. The components of this coupling, V-grooves and the balls, are made of stainless steel and have a hardened surface by the kolsterising process. The position repeatability is calculated to be approximately 1 micrometer.
Clamping of the workpiece holder is done using permanent magnetism. A system is designed which makes it possible to clamp and unclamp the workpiece holder after placement. The big advantage of the magnetic clamp is that it works contactless and therefore without interfering forces.
The frame of the workpiece holder will be made of Invar. The first prototype is made of stainless steel to make easily changing of geometry possible. To reduce costs the frame exists of plates made by waterjet cutting. The cost price for a workpiece holder is approximately 200 euro. The first natural frequency mode of the workpiece holder is 270 Hz assuming a workpiece mass of 1 kg.
The material choice for the frame of the workpiece holder is mainly done by analyses of the thermal behaviour. Both aluminium and Invar are holding their shape during temperature variations. However, the linear expansion of Invar is much lower, which is important because the workpiece holder is part of the metrology loop. The total thermally induced error of the workpiece holder is in the order of a few nanometres.
Prototypes of the magnetic clamp, three V-groove coupling and workpiece holder are made. The magnetic clamp force of the prototype is already tested. Position repeatability of the coupling still has to be tested.