Chastec provides the high quality for safety in Saab

It's obvious that the quality assurance procedures for the individual components which go to make up a car are of considerable importance. This is why Chastec is using a pattern matching sensor at several stations on its production line for monitoring the steering systems which it manufactures.

Chassis Technology Mülheim GmbH, a 100% subsidiary of Mercedes-Benz Lenkungen GmbH, is a leading manufacturer of steering systems for cars. Its client list includes a number of well-known car manufacturers such as DaimlerChrysler and Saab, who have high quality requirements for the steering systems they use, which are crucial to the safety of the car.

O-ring identification in steering systems for the Daimler C class

The O-ring in the rotary valve is used to seal the lower pressure chamber. It is put in place manually by a production line worker, which means that variations of a few millimeters in its position are possible. The valve is then placed on a seat, where additional play of around 1-2 mm may occur. These tolerances can add up to several millimeters.

The conventional laser sensors used in the past produced incorrect results because of the point sampling method used. The system reported that the O-ring was in place, even if the O-ring was not there. As a result of assembly tolerances, the edge of the seat was identified as being the O-ring. An incorrect result can have a crucial impact on the safety of the steering system. If the O-ring is missing, oil will leak from the steering system.

100% accurate results using surface testing

Instead of using point sampling, a surface testing process was needed to produce sufficiently accurate results. To accommodate the tolerances in the height of the O-ring, at least three laser sensors would have been needed. In addition to the high costs and the additional assembly work, there would have been problems with fine adjustments later in the process. A visual inspection system would have been too expensive. Using the pattern matching sensor for surface testing was a safe solution which could be implemented quickly, was easy to use and offered the security of visual inspection.  

Material flow checking for Daimler E class steering systems

Four versions of the steering system for the Daimler E class are being manufactured on a new production line. These are right-hand or left-hand drive systems which are either standard or configurable (speed dependent). At the start of the production line is a station where the steering box is fitted by hand. Before the component moves on through the remainder of the manufacturing process, the type of steering system must be defined. The first check identifies whether the steering system is for a right-hand or left-hand drive car.

A second check follows to determine the design of the system, that is, whether it is a standard or configurable system. These two checks allow the steering box to be clearly identified by means of the holes drilled in it. The last stage involves checking for the presence of the corresponding type plate.

The pattern matching sensor produces guaranteed results

Conventional sensors were previously used to carry out these checks, but once again point sampling produced incorrect results. Time-consuming fine adjustments and extremely careful positioning of the steering system did not produce sufficiently accurate results. Now four pattern matching sensors are used for all three quality assurance checks. This sensor can be used to check several criteria because of its memory banks. After the two outer sensors have identified whether the steering system is right-hand or left-hand drive and the standard or configurable version, the two inner sensors check the type plate.

The pattern matching sensor has shown its worth in this application because it is easy to fit, does not need fine adjustments, produces guaranteed results and can be put into action quickly.