Profiled Workpieces

Profiled workpieces made of plastic, rubber or aluminum are required in the construction of vehicles (door and window seals, aluminum spaceframes), in the building trade (window profiles) and in automation systems (belt profiles, assembly modules). In the extrusion process, complex profiles can be manufactured at a comparatively low price. In addition to the form tool, the mold pressure, pressing speed and surface roughness also influence the final form of the workpiece.

It usually takes only several hours to manufacture a batch. Since large quantities are often produced, it is essential to check the quality of such workpieces as quickly as possible after they are pressed. Time-consuming manual programming is therefore out of the question. The CAD data must serve as a foundation. There are basically two possibilities. The measurement plans can be created either immediately before manufacturing the batch or during the design process via Werth Cad-Offline® programming. The precondition for this is, however, that quality assurance is a component of the production or production planning operations. In most cases, the operators of the measuring machines are not adequately qualified to deal with complex coordinate metrology tasks. Help is provided in the form of suitable operator prompting and graphic output of the measurement record in the form of a drawing with the actual dimensions. Special standards for aluminum extrusion molding (tolerances) and plastics (special linkage of contours) must be taken into consideration when programming the measuring software.

For fast inspection of profiles, optical scanning can also be combined with the ToleranceFit® software. In this method, the contour of the parts is checked with a gage. The prerequisite by the design for achieving this is to convert the form and size tolerances usually specified department in numerical form to a contour-related tolerance zone system (Fig. 59) which is better adapted to the manufacturing process.

Fig. 59: Basic example of the relationship between contour tolerance zones and form or dimensional tolerance.

The definition of the tolerance structures, especially regarding the reference systems, should be coordinated between the manufacturer and the customer from the beginning. The main advantage of this second inspection procedure is function-related measurement. The output is easy to survey and provided in a graphic form. This enables operators who have not received any special training to operate the system.

Similarly, the tool correction used when inserting new tools can also be supported by the BestFit software. The selection of the system technology suitable for this measuring task must be based on the drawing tolerances of the profiles to be checked. Tolerances ranging from several tens of micrometers to maximally 0.1 mm are the rule. As a result, measuring uncertainties of 5 µm to 10 µm are often sufficient. However, this applies only to general distance dimensions and diameters.

Since the measuring task is two-dimensional, optical measurement with image processing can be performed quickly. It is important to deburr the parts. Any remaining burrs are, however, suppressed by suitable image processing filters. The most user-friendly option is a device which allows the profile sections being measured to be placed on a glass plate (Fig. 60). No time-consuming refocusing is therefore required. Below the glass plate is a camera which can be moved in two coordinate directions and which is focused on the glass plate. The transmitted-light source is located above the workpiece. Since it takes only several tens of seconds to measure a complete profile, the manufacturing process is not held up for any length of time.

Fig. 60: Machine for measuring aluminum profile sections (Werth FlatScope 400).