Less rejects despite complex geometries

Bosch manufactures the starter armatures on seven assembly lines. In the first step, the coiling elements are made of copper wire and cut into the right length. Afterwards, they are formed into their final shape. The geometry of the coiling elements may seem to be very simple at first glance. However, it is complicated to check if the reshaped element is true to gauge. In contrast to conventionally bent tubes and wires that arithmetically consist of lines and bends and have constant radii, most of the coiling elements have no fixed parameters. Due to the special forming process, the bends change continuously. Thus, theoretically, different radii could be present at each point of the part. These so called free-form geometries cannot be measured by conventional measurement technologies.

Yet it is absolutely necessary to comply with the ideal geometry of the coiling element. Otherwise, further processing is not possible. For example, the two end fittings must have exactly the same length, or the coiling element cannot be used for the starter armature.
The responsible planner reports: “With TubeInspect HD, we are now in the position to immediately detect and correct the slightest deviations of the coiling elements to their nominal geometries. Moreover, the subsequent production steps have become a lot safer.”

Freeform measuring principle

TubeInspect HD is dedicated to measure small tubes and wires. It merely requires that the coiling element to be measured is placed in the optical measuring cell. High-resolution digital cameras accurately measure its geometry in ten seconds. For the measurement, the system reverts to the integrated free-form measuring function that creates a solid model. TubeInspect HD compares the measurement results against the nominal geometry and the preset tolerances that are stored in the system. The result is reported in a color-coded way so that the user immediately gets the information if the element under test meets the requirements, or if any deviations occur. If required, the worker can instantly arrange for the changes of the concerned tools.

The responsible person for the production of the coiling elements explains the benefit: „Tanks to the measurement, we are now able to look for manufacturing errors systematically. Additionally, it is possible to compare the results of different assembly lines on which the same product is manufactured. We in the production like to use our new system. The fast comparison is really convincing.”
Bosch conducts these measurements in random checks during all three shifts as well as in case of breakdowns and model changes.

Using synergies – application in construction and series production

However, the system is not only used in series production. It has also proven its worth in Reverse Engineering. “In the area of construction, Bosch applies TubeInspect HD for the measurement of sample parts or for the optimization of existing coiling elements”, explains AICON project engineer Matthias Kneschke who has installed TubeInspect HD at the Bosch’s plant. “Moreover, Bosch uses the measurement data of TubeInspect HD for the manufacturing of the production tools.
Prior to the construction of a tool, the ideal shape of the coiling element has to be defined. For finding out this ideal geometry, the members of Bosch’s technical staff cannot only rely on the construction data. In fact, the engineers also have to bear the subsequent production processes in mind. Matthias Kneschke illustrates the procedure: “The generated ideal geometry serves as master piece. This geometry is measured with TubeInspect HD’s so-called master measurement and stored in the data base of the system. Afterwards, in series production, Bosch uses the data as a basis for comparison with the manufactured coiling elements.” The tools are based on the results of this master measurement, too, as the master data can be exported in the STEP-format which is compatible to CAD. Thus it can be forwarded to the tool constructing engineers.