Versatile use of the Leitz PMM-C Ultra with small precision parts

SFS Intec - Switzerland

Before a precision moulded part, a special screw or a movement element can be installed in the end product it must go through several process stages. At SFS intec development starts with the agreement of a customer‘s construction drawing. The aim: to ensure by working closely with the customer that each part works properly and can be manufactured economically. Whether it is a gear for a chain drive in a motor, a miniature screw for a mobile phone or a gearbox component for a drill. Furthermore it is the task of the developer to design the part so that it can be manufactured using powder metallurgy or cold forming – technologies that are used at Heerbrugg. Above all for complex geometries SFS intec prefers to use powder metallurgy. When it is a matter of parts with high strengths in series production, SFS intec turns to cold forming.

Metrology in tool-making

PC-DMIS-SFS-intecCrucial to the quality of the parts that can be produced using cold forming – like pinions for starters or belt systems – is the quality of the tool. The correct design of the punch and die is the responsibility of the engineers in the technical office at SFS intec. Grinding, die sinking EDM, turning and milling are also part of a toolmaker‘s work. The tools are inspected using two Brown & Sharpe coordinate measuring machines, both Chameleon models, which have been part of the machinery park since 2000. Until the acquisition of the Leitz PMM-C Ultra five years later, many measuring tasks were completed on these coordinate measuring machines. The continuously rising requirements of the customers – above all coming from the automobile industry – is paralleled by the growth in performance of coordinate measuring machines themselves. The requirement for a more precise machine arose from the need to master even more complex measuring tasks. The choice of the Leitz PMM-C Ultra was based on its good price-performance ratio, high accuracy and speed. The machine‘s high accuracy in scanning mode was particularly impressive.

The Leitz PMM-C Ultra at SFS intec has a volumetric length measurement deviation of 0.4 + L/1000 µm and is installed in the climatised room. Matching the approach of the company to small parts, the staff working in the field of metrology at SFS intec use the Leitz PMM-C Ultra as standard with probes with a diameter of 0.5 millimetres. In addition to PC-DMIS, for tooth geometries and other complex shapes, metrology personnel make use of the measurement software QUINDOS. The Measuring Range is 1200 mm x 1000 mm x 700 mm.

Support during development...

The use of the Leitz PMM-C Ultra is characterised by diversity at SFS intec: the CMM is used for the inspection of gauges, acceptance, random inspection of series production and complex parts from the production floor, in addition to initial sample testing and process analysis support.

Large batches of parts with tool-related dimensions are inspected at SFS intec using a 100% mechanical process, smaller batches by the production operatives themselves using gauges. The advantage of gauges lies in their simplicity of handling and time-savings. The metrology staff plays an important role in the development of the gauges. “We generally do not need a highly accurate 3D measuring machine for inspecting series produced parts. Pressed parts are not produced to tolerances of a micron. For customers it is much more important that all parts are identical so that they can be installed by automatic machines. The parts need to be checked for proper function and for this gauges are ideal. We use gauges to check toothing geometries in production, e.g. the complete profile.

The tooth width and the internal diameter of the part. The gauge must be applied exactly in the correct position and are manufactured to a tolerance of 5 µm. To measure the gauges themselves, we depend on a highly accurate coordinate measuring machine such as the Leitz PMM-C Ultra,” explains Walter Vetter, Metrology Team Leader at SFS intec in Heerbrugg. During the start-up phase of a project, metrology technicians have another important role: “For initial sample testing we also use the Leitz CMM,” says Metrology Technician Urs Köppel. As the throughput time for the manufacture of an initial sample is very short, testing of the sample also has to proceed at a fast pace. Gauges cannot always be used at SFS intec in these cases. If the design is changed slightly just before manufacture of the sample, this would mean it was impossible to make new gauges in time. The Leitz PMM-C Ultra is therefore the right tool for initial sample testing in terms of speed and precision.

...and in production.

SFS-Intec-InspectionLater, during the production phase, the metrology team make further use of the highly accurate measuring machine: “We support various sections in the company with the Leitz PMM-C Ultra. This support begins in development and carries on in production to know, for example, how a particular point on the surface had changed from one step to another. We needed to prove that this point remained in the same position, in the same alignment and at the same height. Using this machine from Leitz we found we were able to carry out this type of analysis and modify the production process so that the parts eventually passed. In the case of the above part we discovered that we had to press the part outside of the manufacturing tolerances.  During reworking, excess material was then removed by turning, which allowed the material to relax and bring the part back into the tolerance range within which we had to work,” explained Walter Vetter. In this case as well, the Leitz PMM-C Ultra proved an important tool for process improvement. And Walter Vetter adds: “A further plus point in remaining with Hexagon Metrology was compatibility with the existing machines. We use PC-DMIS on all our machines. In addition we receive support for our users of Brown & Sharpe machines and for our users of the Leitz PMM-C Ultra from a single company. Thanks to the Leitz PMM-C Ultra, we can now carry out measuring tasks which previously we would not have found feasible.”

Random samples from production series are tested with this CMM,” says Urs Köppel. Complex parts that cannot be tested in production find themselves on the granite table. The realisation that the team gains from the inspection of complex parts feeds directly into production. The metrology technicians are therefore in a position to give valuable assistance to their colleagues in production. They can determine, for example, whether the die or the machine settings need to be changed. In the end the manufacturing processes and therefore the quality of the parts are improved.

Optimisation of the production process is also the focus of targeted process analysis. With processes that have led to defective parts, the Leitz PMM-C Ultra makes it easier to place the suspect process under the microscope and rectify the source of the defect. “For one customer from the diesel sector we produced a part that consisted of a plate and a shaft. In the final manufacturing stage the plate kept distorting. We put the spotlight on each stage in its production by measuring the part after each step. This meant we could dispense with the conventional shape and positional tolerances such as parallelity and rectangularity.

Then Continuous process improvement and process control with high quality are the objectives that SFS intec set out to pursue. The Leitz PMM-C Ultra helps the Metrology Team every day to achieve these objectives in real terms. The highly accurate coordinate measuring machine will ensure that SFS intec can continue to press, turn, grind or roll products without problems in the future.