Highest precision in the μ-range

Efficiency, comfort, consumption, environment, sustainability: The 8-speed automatic transmission 8HP by ZF presents itself as one of the most modern and, above all, most economical multi-ratio automatic transmissions on the market. The increased spread and the finer gear graduation reduce consumption by six percent, for example, compared to the 6-speed transmission; further savings are possible with hybrid elements. "However, it would be wrong to see the 8HP as a pure 'economy transmission'," explains Gernot Röpnack, who is responsible for gauge planning at ZF AG's Transmission Business Unit. Extremely short shift times and good shifting comfort are just as crucial.

For this reason, the highest demands are placed on the precision of the automatic transmissions at the ZF plant in Saarbrücken, both during production and assembly. Uwe Lydorf, responsible for measuring equipment planning, adds: "The 8HP transmission is a completely new development and is assembled from many individual parts; the interaction of all parts up to the operational product is a complex process with the highest precision requirements, not only during assembly: Axial, clutch, bearing, differential, or gear backlash

Measurement technology for process control

must be adjusted and tested. Since the overriding goal is also economical production with a high yield of good, we have, for example, set up numerous series-accompanying testing and measuring devices in all pre- and final assembly lines."

Proven supplier at ZF

For many years, ZF has relied on a proven specialist in gage construction, Oberndorfer Präzisions-Werk GmbH & Co. KG (OPW) with more than 60 years of experience in production measurement technology. Over the last three decades, the Swabian company has shifted its core competence from standard gauges to special gauges and measuring devices with a range from simple good/reject gauges to semi-automatic SPC measuring stations, as well as the latest product in the high-end sector, the OPW-R1 robotic measuring cell. Today, as a full-service provider, OPW GmbH is one of the leading gauge manufacturers. Gernot Röpnack: "An essential part of the ZF company philosophy is long-term partnerships with customers and suppliers, which are characterized by cooperation, communication and mutual trust - OPW GmbH has also been a reliable supplier for several years as a strategic partner in the ZF Group. »

Manufacturing depth of over 98 percent

Approximately 1.9 million gearboxes are produced annually in Saarbrücken. 

Transmission know-how valued worldwide

For the extensive testing and measuring tasks in the 8HP transmission assembly lines, most of which go beyond the standard, ZF uses almost the entire range of OPW measuring technology: from setting masters and setting rings to limit plug gauges and complex SPC measuring stations. OPW Managing Director Uwe Hildebrandt: "Metrological measures for process control are what make the reproducible and error-free production and assembly of the automatic transmission possible in the first place.

Long service life thanks to dimensional stability

but also a great deal of know-how. We see ourselves as a problem solver of metrological requirements and as a full-service provider. " All measuring devices are completely designed and produced at the OPW plant in Oberndorf. "The in-house design as well as the high vertical range of manufacture of over 98% are far beyond the possibilities of ordinary gauge construction and thus represent a clear unique selling point of our company," says technical project manager Martin Leicht. "We deliberately focus on creating value in-house."

High precision setting masters

With the help of the setting master, for example, the correct position of the pinion shaft is determined. "The tuning of the bevel gear teeth is elementary for the noise behavior and the durability of the transmission," explains Kai-Uwe Jung, responsible for gauge planning at ZF. "The necessary position masses are produced with the help of shims. For bevel gear setting or positioning, a high-precision setting master is required to know where the "zero" is. Some suppliers have already reached their limits here - only OPW was able to meet our precision specifications exactly." However, the Swabian gauge manufacturer is also in constant competition and must prove itself anew with every product.

Measuring devices for clutch adjustment

Generally, this type of measuring device is used as an auxiliary tool for setting necessary "clearances" within the transmission. This is the "clutch free play adjustment". These measuring fixtures (form and position tolerances < 5μ) are used for prototype assembly and in-production inspection of measuring stations. "On the one hand, the OPW measuring devices convince with their long service life due to their dimensional stability, and on the other hand, continuous testing equipment examinations in our precision measuring room run almost without any complaints," says Patrick Schumacher, who is responsible for measuring equipment planning at ZF.

It just fits

Gernot Röpnack draws a positive conclusion: "Even though OPW has been one of our strategic suppliers for many years - almost every order presents a new challenge. In addition to many years of experience and excellent technical knowledge, the employees convince us time and again - through flexibility and willingness to innovate, specialization in special gauge construction, but above all through reliability and helpfulness and by the fact that support is not neglected even after the purchase." Uwe Lydorf adds: "We are also committed to our customers: In gear technology, quality, flexibility and competence arguments dominate; in addition, our demands on the precision of the highly complex measuring devices are extreme, in short: the smaller the dimension, the more precise the accuracy of OPW products."