QMT Features: October 2011
Gauge-less testing of brake lines
Product specific gauges are a thing of the past in the bending of tubes – the new trend is for gauge-less production.

The need to withdraw from the use of physical gauging devices for tubes is not surprising, because their procurement and maintenance play a major factor in production costs. This is particularly true when considering the need for technical modifications and change of models, as re-engineering mechanical gauges is generally not possible or at least extremely cost-intensive. A universally deployable inspection system, on the other hand, provides rapid payback as it allows the tubing to be gauged immediately. Furthermore, any assessment of tubing quality with the help of a physical gauge is a very subjective matter: already the ‘personal disposition’ of the tester can be decisive as to whether the tube is classified as a good or a bad part.

This assessment was recognized by Dr. Andreas Röher, technical director of Tube Technology Systems AG (TTS) from Massen, Germany. TTS has been manufacturing PA-sheathed steel pipes for use in brake line manufacture since 2004. With a staff of 65 at that time, the company made a name for itself with the patent of a special bolting system for installing brake lines in the vehicle’s designed space.

Up until this development, steel pipes already equipped with fittings were sent for machining directly to the car manufacturer bending centres or to 3rd party tube bending companies and ultimately, following the bending process, on to car manufacturers for final assembly. TTS was able to observe that tube benders customarily tested the dimensional accuracy of the remodelled tubes by means of mechanical gauges, with typically several gauges generally being needed per vehicle type. Their production was time-consuming and consequently cost-intensive, with the bent tube being placed for testing in the measuring device and judged visually as being good or bad.

In addition there was no auxiliary device available which could accelerate setup of the bending machine. To a certain extent, usability could only be tested on the finished car body. Changeover to a new tube production, i.e. correct adjustment of the push, rotation and bending parameters, often occupied some hours and was extremely dependent on the skills of the operator of the bending machine.
In the course of a company reorientation, and after careful deliberation, TTS AG decided to add the bending process to its own portfolio in addition to pure tube manufacturing. Recognizing a high potential for improvement, an innovative business concept was subsequently worked out based on optical measuring systems, thereby rendering physical gauges redundant and thereby substantially reducing production costs.

As car manufacturers themselves customarily bear the costs of measuring devices, the TTS concept offered a clear competitive advantage compared to long-established suppliers with conventional gauge technology.
To accomplish this concept, Dr. Röher already had the appropriate optical measuring device in mind: the system TubeInspect* made by AICON 3D Systems GmbH, which checks tube geometries and transmits comparison values directly to the linked bending machines in a matter of seconds. Sure enough, TTS AG quickly received positive feedback from its customers, as Dr. Röher explains, “The concept was convincing for car manufacturers, as there was no longer any need to have to procure gauges. Business-wise that was naturally extremely interesting for our customers”. But it wasn’t commercial arguments alone that satisfied the car manufacturers. With the process capability of the overall concept, TTS was also persuasive technologically. The complete manufacturing chain was examined by the car manufacturers - from the production of shell construction lines, to the bending process with Dengler bending machines, all the way to quality controls by means of optical tests. In line with the concept, two bending centres subsequently launched operations:  the first in 2009 in Europe and the second in 2010 in the USA. Brake lines here are bent in the immediate vicinity of the car assembly plants, measured by means of TubeInspect and delivered within a narrow time frame thanks to the short transport routes.

A further advantage of TubeInspect is the saving of cost-intensive and generally time-consuming coordinate measuring technology for sampling. Optical testing allows the coordinates of the bending points to be determined within seconds.
The TubeInspect measuring system is specially designed for geometrically measuring remodelled tubes and wires and can be deployed in reverse-engineering as well as in prototype construction or series production. In addition, the system determines within seconds the setup and correction data times for the bending machines. Corrections can be transmitted immediately by TCP/IP to the tube bending machine, thereby eliminating time-consuming setup times. In this way TubeInspect replaces a number of conventional mechanical gauges. The measuring procedure is extremely simple. The brake line to be measured is placed in the measuring cell, the process started, and within seconds the results are visible onscreen: pass or fail. The measuring cell is available in two different sizes depending on the dimensions of the line spectrum to be measured. TubeInspect has a measuring range up to 2500 mm x 1100 mm x 700 mm, is suitable for tubes with diameters of 3 to 200 mm and can register bend angles of 1 to 180 degrees.

The tubes to be measured are simultaneously acquired by up to 16 digital cameras, and by virtue of the large measurement volume even long and complex tubing is easily measurable. The system can measure complicated tube runs, like bend-in-bend and free-form bends, and is also designed for automated 100% control. In this case, a robot can remove the bent part from the bending machine, and while holding it in the measuring cell, the measuring process starts automatically - the finished tube can immediately be graded as a good or bad part.
By utilizing the AICON optical measuring system, TTS AG has successfully positioned itself among the previous players in the car manufacturer supplier segment. For Dr. Röher, “This was the perfect opportunity for applying gauge-less production”. TTS still has some plans for the future, says Dr. Röher. “More sites for gauge-less production are planned to be launched. With a concept of this calibre, it is easily quite conceivable”.l


*TubeInspect is available in the UK from Measurement Solutions.



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