Measurement of free-form surfaces made easy
- Messkomponenten

Measurement software FormControl, CNC touch probes and laser measuring systems from BLUM at Pfaff Molds

Today, highly complex sealing systems, adapted precisely to the actual application, are used to optimise aerodynamics, minimise wind noise and, last but not least, ensure the body is sealed as tightly as possible. The ideal injection moulds for this are provided by Pfaff Molds. BLUM’s FormControl software and touch probes enable the southern German company to fully measure the milled moulds while still in the machine.

Automotive sealing systems consist either, as in the past, of extruded profiles or of highly complex connecting parts that, for example, not only seal the glass in the front lower corner of the side window but also cover the transition from the outside mirror to the door. Cut-to-length pieces of the extruded profile are inserted into the moulds at Pfaff Molds and then injection moulded into the mould cavity with the corner geometry using rubber material or TPE. After opening the mould, a rubber or TPE part seamlessly connects the various profiles. “Precision is crucial when it comes to moulds. The extruded profiles must be positioned very precisely in the mould insertion areas and the mould must also close exactly to prevent injection material escaping between the two halves of the mould and forming burr,” explains Stephan Baldauf, milling department manager. “In addition, customers place very high demands on the accuracy of the parts and their surface quality. We manufacture the moulds to tolerances of one hundredth of a millimetre.”

Pfaff offers its customers a complete package that ranges from mould design and manufacture, to production of sampling and first parts, and finally development of an injection moulding process that is precisely adapted to the customer’s materials. For this purpose, the German company operates an array of injection moulding machines to be able to develop the injection moulding process on a machine that is identical to the customer’s. Actual series production of the sealing systems takes place at the vehicle manufacturer’s factory.

The required accuracy and the high surface quality that the moulds must display demand very long machining times, even for small moulds. Machining times of up to 100 hours on a single mould plate are not uncommon. That is why the ability to work reliably and unmanned, both on weekends and during the night, is very important for economical production. The thirteen machining centres are, therefore, equipped with Blum-Novotest’s FormControl software, which enables automatic 100% quality control. In addition, laser measuring systems, mainly used for tool breakage detection, as well as touch probes for workpiece measurement are installed in every machining centre.

FormControl represents a simple solution: The measuring software allows the operator to define the points to be measured on the CAD model, thereby enabling the definition of measuring points on a PC. With free-form surfaces, the actual contour should match the CAD model as much as possible. After automatic feedback of the measurement results, FormControl displays deviations from the ideal form by detecting various individual points using the target vs. actual method. If desired, the deviations can also be displayed on the screen via arrows or coloured dots. Needless to say, the data can also be output in table form as part of a measuring report. Measuring in the original set-up offers a major advantage: If excessive deviations are detected when measuring with FormControl, the workpiece can be machined again immediately until it is within the desired tolerance limits. Free-form surfaces, like the ones frequently found on Pfaff moulds, are particularly challenging to measure. The use of conventional measuring machines for this task can be costly in terms of both time and money.

It often becomes apparent during the process development phase that the mould needs changing. The machine operator can then use FormControl to record the current geometry and set the zero point of the milling program accordingly: This allows for an area of the mould to be reworked precisely without creating errors to the existing geometry. In addition, material can, if necessary, be welded on, the new geometry measured and used as a blank for NC-programming.

FormControl helps Pfaff deliver the high precision that its customers expect in numerous areas of application. In summary, Stephan Baldauf says: “BLUM supplies extremely practical and high-quality products, both in terms of their hardware and software, which simplify our everyday work and save a great deal of time and effort. This is of enormous importance, especially in our sector, where delivery times are increasingly shorter and customer demands are constantly growing. For us, the simple operation of FormControl is essential, as a lot of programs and protocols have to be created quickly – for ‘batch size one’ products.