Several million plastic parts per year are tested in the production halls of a well-known German-based manufacturer of small electrical appliances, which ensures the quality of the electric shavers and epilators as well as the success of the brand. The company has made a name for itself through its product design and has taken a significant place in the history of industrial design. The company was an international pioneer in the design and shaping of consumer goods. The brand is now part of the portfolio of a major US consumer goods group.

Today's market-leading electric shavers are complex products consisting of 200 to 300 individual parts, some of which are very delicate, depending on the type. To ensure quality, each of these parts must be almost perfect, but 100% reliability is difficult to achieve. With automatic testing and sorting machines from Vester, the company can ensure very high quality and functionality of the components in the end product. Figures show that comprehensive quality monitoring during and after the production process has made it possible to significantly reduce the internal complaint rate. Comprehensive quality monitoring has had an equally positive impact on warranty claims, the rate of which is now also considerably lower.

Precision at high throughput rates

Just three automatic testing machines from Vester test and sort several million plastic parts. Parameterization via touchscreen or keyboard (center) and automatic sorting or batching (left) are integrated.

© Kistler

Three Vester testing and sorting machines are currently in use in the plastics area; a feasibility study is currently being carried out for a fourth. Eight further systems are located in the automatic turning shop, where they test, among other things, supplied metal parts such as the pins that are installed in the head of the razor and in the electric toothbrushes and ensure performance and output.

The demands on testing performance and speed are particularly high in the production of plastic parts. In order to achieve the required precision and high throughput at the same time, it is essential that the individual parts are fed and aligned in the correct position. Parallax errors must be avoided. Parallax errors are measurement errors that occur because the angle of view of the camera is not exactly on the optical axis.

Universally applicable systems

All Vester inspection and sorting machines have a modular design and can be equipped with different cameras, feeders and handling systems depending on requirements.

© Kistler

Two VVC 120 systems (inclined plane inspection principle) and one VVC 811 system (continuously rotating glass plate) are currently used in the plant to inspect and automatically sort several million plastic parts: Are the components deformed? Are there any burrs? Are the specified dimensions and tolerances achieved? Particularly critical components that are central to function and performance are tested.

The flexibility and performance of the Vester systems are crucial for the electrical appliance manufacturer. With an appropriate setup, not only can several features be tested on one component; different components can also be tested on one system without major effort. Vester is on hand to assist with application changes and offers the option of reconfiguring the camera and feed systems on site or - in the case of major conversions or retrofits - at Vester itself.

Close cooperation with Vester is necessary in order to meet the high requirements of the parent company. This is because standard automatic testing machines must be adapted for each application. Taking into account the complex geometry, demanding testing requirements and high quantities, Vester has found a solution that is both economical and conducive to the customer experience.

Test results allow process optimization

The manufacturer of shaving and epilating appliances has already had many years of good experience with automatic testing machines for metal parts. Another advantage offered by Vester systems that should not be underestimated is in-house testing. The know-how gained by the customer about certain recurring deviations allows conclusions to be drawn about the injection moulding process and enables measures to be taken to optimize the process. With the systems installed by Vester, for example, it is easy to check which cavity a faulty part comes from. To do this, the corresponding identification is read out and it is possible to specifically investigate where there is a problem in the process and make targeted improvements.

Efficient process monitoring plays a key role in the course of further optimization and automation. Only in this way can the manufacturer predict a service life of up to seven years for its products in the future.

Author:
Samuel Ganzhorn is an Application Engineer at Vester - A Kistler Group Company in Straubenhardt, Germany.

The automatic testing machines

In August 2017, Vester Elektronik was acquired by the Kistler Group, which is continuing to develop the portfolio. Since the beginning of 2019, all former Vester products have been trading under the Kistler brand.

The machines in the 'KVC 121 series' (current generation of the predecessor model 'VVC 120' since the takeover of Vester) test test specimens on a test rail in motion using camera measurement technology and then sort them into good and bad parts. The universal testing and sorting machines can be equipped with up to four digital cameras with different resolutions and can be expanded with additional accessories depending on the task. For example, a hardness test can be integrated.

The 'KVC 821' testing machine (current generation of the 'VVC 811') tests series parts on a permanently rotating glass plate. Depending on the test result, the test parts are sorted into good and bad parts at the corresponding sorting station. The solution can be equipped with a maximum of eight camera stations. The integrated 'Trevista' incident light dome illumination is based on 'Shape from Shading' technology and inspects the surface of components for the smallest defects. The inspection machine also features an industrial PC, the in-house image processing software 'KiVision' and a corresponding HMI. Depending on the size and weight of the test specimens, the feed system is either integrated or provided. Other functions such as a hardness test or 3D measurement technology can also be added.

The 'KiVision' image processing software integrated in both test stations ensures that test tasks can be set up quickly and easily. In addition to all common methods of image-processing testing technology, the software offers a wide range of tools and ready-made macros. This allows demanding measurement tasks to be mastered and measuring and attributive evaluations to be carried out. However, the software goes beyond pure inspection tasks: it enables the consistent recording of data, which is becoming increasingly important in view of the growing requirements for the traceability of products. An additional export module allows measured values to be transferred to external CAQ systems. Integration into the company's own network means that inspection programs can be conveniently managed centrally.