Saving Money at Full Speed

Zelter GmbH is a major sub-supplier to the automotive industry. Established in 1923, they are considered a solid player/partner in the marketplace. They supply batches, such as exhaust manifolds, hubs, parts for steering gears, brake and belt pulleys and housings for turbo chargers.

Though Michael Kiehl's production department is working in three shifts of 7.5 hours each, Zelter is working to full capacity. Every week up to 20,000 parts are produced. On average, two trailer trucks per day supply the semi-finished cast components that are necessary for such high output.

"Usually the dimensions of these cast parts vary by 2 mm," said Kiehl, "each one is different from the following one." Therefore, the position of the surfaces, bores and channels that must be machined vary when they are clamped into the machine tool. At present, Zelter is working with 34 machining centers. The travel distances are up to 800 mm. One half of the machines is equipped with TC51-20 touch probe systems by Blum-Novotest GmbH (Ravensburg); the other half with Blum Z-Nano and Z-Nano IR tool breakage control-type systems. Blum measuring technology generates the conditions for the economic serial cutting operations of these cast parts of varying dimensions.

Up to the end of the '90s, Zelter first milled orientation surfaces on the gas inlet and outlet of the semi-finished products within the tolerance of the material allowance. The disadvantage here was that this was on a separate machine, one that did the roughing, and the reference points could be lost as the part was subsequently was transferred to the production machine.

Efficiency by Blum
The measuring technology by Blum is remarkably efficient. The touch probe TC51-20 is set into the toolholder of the CNC machine and detects single points of the geometry of the cast parts, i.e. the actual data, and transmits them by infrared transmission to the control of the machining center. The CNC compares these with the coordinates in the part drawing, the set data, and calculates the position of each zero point. If this is a bore, for example, each workpiece of the series has its own reference point. Or, you can say, by detection of the reference points of the semi-finished tool, the machine tool "knows" where to start.

Tremendous Time and Precision Savings
Potential savings are tremendous, when the semi-finished products are set and measured and then finished on the same machine (which at present is just theoretical, but entirely possible). For the present, Zelter roughs and finishes their parts on two different machines; the remaining tolerance is between 0.4 mm and 0.5 mm. The reason for the use of two machines, however, has nothing to do with the Blum measuring technology but rather the craggy geometry of the housings and the resulting interrupted cuts.

So far, Zelter is roughing and finishing on different machines and detects each workpiece zero point on the corresponding machining center with the TC51-20. The substantial savings compared with the former handling are still tremendous. By the end of the 90s, Kiehl equipped his machines for the first time with probe systems by Blum.

"At that time it was the best you could get on the market, and this still hasn't changed today," he said.

Probing Speeds up to 5m/min
Today, the company prefers the TC51-20 with its acceleration of up to 100 m/sec2. However, such values are hardly achieved by any machining center. What pays off is the rapid probing speed of 5 m/min. Depending on the complexity, the TC51-20 detects within five to ten seconds the reference points of parts with a length up to 500 mm, which is a considerable distance one from another. So, essentially the capacity increases.

Coolant and pollution have no influence. The enclosure corresponds to IP 68. The handling couldn't be simpler: the TC51-20 has a standard ABS-50-interface, and it is placed like a common tool in the tool magazine of the CNC machine and changes into the working area for measurement.

The probe system works bi-directionally. Zelter can carry out all necessary measuring operations. Besides the usual measurement into the beam, measurement out of the beam is also possible with the TC51-20 due to its innovative measuring system. This is an advantage for Zelter as the probe system can exactly detect the spiral insides of the turbine housings. Data transmission is wireless. The information is transferred by infrared to an IC 55 Blum receiver in the working area. Its enclosure corresponds also to IP 68. This receiver then forwards the data to the CNC of the machine tool.

Up to 235,000 Measuring Operations with One Battery
With a standard 9-volt-battery, the TC51-20 works independently from external current sources. In practice, up to 235,000 measuring operations are carried out with one battery. According to Kiehl, his colleagues have been by and large entirely "unconcerned" about the system. In a case where the battery might be "failing" early, the probe sends a warning signal to the machine control. Furthermore, the LED gives information about the actual operating conditions.

Protected Against Chips and Coolant Grease
The probe system is ruggedly designed; therefore, it can be used with high-speed on machine tools and machining centers without any deflection of the measuring system. Thus, there are no undesired trigger signals or mechanical damages on acceleration or deceleration. Additionally neither pollution, nor chips, nor coolant will influence its reliability. Despite the measuring value resolution in the range of thousandths of millimeters, the TC51-20 is indestructible under the harsh production conditions in daily use.

For years, Zelter has used the Blum Z-Nano IR probe systems for measuring the length of their machining tools and for tool breakage detection. The TC series completes in-process reliability. Both types, the TC as well as the Z-Nano IR series, can be used "in duo," where it is possible to use two TC systems, two Z-Nano IR Duo each, or one TC system and one Z-Nano IR Duo on one machine tool in parallel with another. The detected data will be transferred to the machine control via the IC55 receiver in the working area.

Like the TC probe system, the Z-Nano IR is also protected according to IP 68. This system enables wireless data transfer and works without external current supply. Therefore the probe can be installed into the working area without any further condition, and it can be set between the workpieces without restriction so that the tool to be checked can reach and contact it easily, the company said.

For several years, Production Manager Kiehl has built a trust in the measuring technology from Blum. The Z-Nano IR is working with an internal light barrier, the trigger signal for which is generated without any mechanical switching. Different probe systems, working with mechanical switching principles, undergo considerable wear that is avoided with the Z-Nano. Canting of the measuring surface of the Z-Nano is impossible. The functional principle with linear guides enables very small, fine and filigree tools to be measured, said the company.

This means that for the standard design of the Z-Nano IR, diameters of less than 0.5 mm are normal, and in the "high-precision" arena, even less than 0.1 mm is possible, said the company. The reset, which is set by spring force, is the only mechanically operated feature of the Blum design.

From the manufacturer's point-of-view, like Zelter, every part is really a single copy. Serial machining of these cast parts, which differ by mere millimeters, is only economically feasible because of production metrology like that of Blum-Novotest. Or, as stated by Kiehl, only feasible on "the best technology on the market, Blum."

For more information contact:

Paul Meinhardt

Blum LMT, Inc. Sales

4144 Olympic Boulevard

Erlanger, KY 41018

859-344 6789

Fax: 859-344 6799

www.blumlmt.com

E-Mail: solutions@blumlmt.com

Zelter GmbH

www.zelter.de

E-mail: info@zelter.de