On Machine Free-Form Surface Measurement

Today, highly complex sealing systems, adapted precisely to the actual application, are used to optimize aerodynamics, minimize wind noise and ensure the body is sealed as tightly as possible. The ideal injection molds for this are provided by Pfaff Molds. BLUM’s FormControl software and touch probes enable the southern German company to fully measure the milled molds while still in the machine.

Automotive sealing systems consist either of extruded profiles or of highly complex connecting parts that 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 molds at Pfaff Molds and then injection molded into the mold cavity with the corner geometry using rubber material or TPE. After opening the mold, a rubber or TPE part seamlessly connects the various profiles. “Precision is crucial when it comes to molds. The extruded profiles must be positioned very precisely in the mold insertion areas and the mold must also close exactly to prevent injection material escaping between the two halves of the mold 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 molds to tolerances of one hundredth of a millimeter.”

Pfaff offers its customers a complete package that ranges from mold design and manufacture, to production of sampling and first parts, and finally development of an injection molding process that is precisely adapted to the customer’s materials. For this purpose, the German company operates an array of injection molding machines to be able to develop the injection molding 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.

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The required accuracy and the high surface quality that the molds must display demand very long machining times, even for small molds. Machining times of up to 100 hours on a single mold 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 centers 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 work-piece measurement are installed in every machining center.

BLUM FormControl Software Displays Measured Deviations from CAD Nominal

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 colored 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 work-piece can be machined again immediately until it is within the desired tolerance limits. Free-form surfaces, like the ones frequently found on Pfaff molds, 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 mold 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 mold 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.

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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.”

For more information: www.blum-novotest.com