As well as improving its processes, ZF intends to combat imitations through its policy of marking parts. It set out to find a partner able to handle various marking technologies, with solutions that provide full quality and considerable flexibility for adaptation to manufacturing changes and progressive implementation of internal traceability. The recent order for 4 micro-percussion marking machines raises to 10 the number of machines acquired by ZF from TECHNIFOR for its factory in Friedrichshafen over the last 2 years. The model selected is the TECHNIFOR CN312SM system. Over one-and-a-half million gearbox parts are thus marked each year using TECHNIFOR equipment.
ZF (Zahnradfabrik) is one of the world's leading automotive suppliers for transmission elements and chassis. The company has a staff of 57,000 and owns more than 120 production sites worldwide. Its factory employs a staff of over 7,000 and manufactures, among others, synchronization elements, couplings, planet carriers, and drive shafts.
In recent years, the Friedrichshafen factory has regularly improved its internal traceability processes, on the one hand to accompany the increase in production rates, which are being raised from 750 to 1,000 gearboxes per day in 2008, to meet increased worldwide demand for transport equipment, and on the other hand to combat imitations by making it easier to identify the origin of all parts returned.
Depending on the type of part, and on a case-by-case basis, the company staff decide whether to use simple markings (logo, part serial number, date, hour and minute), or a more advanced Datamatrix solution. In all cases, ZF wanted to install equipment with a long service life, able to accompany it in its traceability programme over time, and providing the possibility of making high-quality DataMatrix markings. The DataMatrix code is a high-density, two-dimensional bar code system that can be used to present a large quantity of information on a small surface. It offers numerous advantages such as high reading speed and high data safety.
The machines put into service by Technifor are of the CN312SM type, with a part position feeler and an automated motor on the Z axis. This provides constant marking quality for a given part model, and enables easy switchovers between part types: the feeler detects its position and the marking head moves automatically into place, without any adjustments, whatever the part concerned. The latest machine supplied features a control camera that checks marking conformity. The electromagnetic stylus fitted on the machine provides high-precision marking at faster operating speeds. In the case of pneumatic machines, the marking tip is moved by compressed air, in natural frequency, whereas a single impact of the electromagnetic stylus is sufficient to indent a precise point on the part. A CN312SM machine is used on the output side of a machining centre with a robotized feed, for instance in the Shaft production department.
"After examining the machines available from the various competitors, we came to the conclusion that Technifor sets itself apart as to the legibility and quality of the marking work provided, under all conditions of use. Technifor is now a standard in our factory, and we consult the Company each time we work on a new project", said Mr BERGMANN, the Production Manager.
Three of the machines supplied were put into service in the Synchronization Elements shop, where 6 million parts are made every year. The lines alternate regularly between different gearbox component production runs, and a flexible solution had to be found. The previous process involved rolling with a mechanical punch. The marking equipment was fixed, and it was necessary to change the tool for each part switchover. The system did not enable parts to be positioned to ensure marking in a solid zone. It was thus necessary to carry out two marking sequences in order to be sure of having one complete mark, because of the surface roughness of most of the parts. "We made a simple calculation; on a production line, we consume 2,000 to 3,000 euros' worth of marking tools per year, and we don't have any flexibility of use. Over 4 or 5 years, we can thus cover the cost of a sophisticated machine like the Technifor CN312SM", added Mr BERGMANN. "The CN312SM enables easy programming of any type of marking, without any specific tooling, and using just one marking tip. With our marking data, the operating rate (up to 180 parts per hour) would be well above the requirements for our long-run production process.
A laser marking project is also under way with TECHNIFOR, for parts with very specific surface treatment, which involve processing numerous items of information concerning traceability. It is necessary to use a laser to encode the data via a DataMatrix to enable the marking of the hardened material.