Efficient production under the most cramped conditions

SITEC boosts its production of transmission housings using five DMC 60 H linear machines in high-precision 24/7 production and three shift operation.

SITEC has been able to install five of the compact horizontal DMC 60 H linear machining centres on a space where only four were possible before.

For 20 years now SITEC GmbH has ranked as the top German address for sophisticated machining of a multitude of different materials. Its range of performance includes the precision machining of series parts for the car and commercial vehicle industry, for example, as well as the 5-axis milling of highly complex individual parts. The company from Korntal-Münchingen recently installed five highly dynamic DMC 60 H linear precision centres to handle the three-shift production and from the very first workpiece onwards has achieved maximum efficiency and accuracy.

“As a supplier we have to convince our customers with our quality and suppler service if we are to survive long-term in this fiercely competitive branch”, explains Ulrich Sigloch, Managing Director of SITEC GmbH. Car manufacturing in particular – a branch where the company generates a large part of its turnover – requires a special quality philosophy. At SITEC this means, “being even better than the customer expects”. Ulrich Sigloch sees several reasons why this is so: “On the one hand we have highly motivated and reliable employees who are well versed in the high level of required expertise and on the other hand our short and unbureaucratic decision-making channels boost flexibility enormously.”

Highly productive 5-axis simultaneous machining with acceleration speeds of up to 1 g and a rapid traverse of up to 100 m/min thanks to the linear drive technology.

SITEC also benefits from this flexibility on a technological level, as Ulrich Sigloch explains: “If you want to ensure modern progressive production, you need high-performance, state-of-the-art machine tools. And we can purchase the equipment we need quickly and simply because we do not have to go through several levels of authorisation for such investments.” In this respect, being an owner-run company often brings an advantage over large enterprises. “This also ensures us a good starting position as a supplier, from which our customers in turn reap sustainable benefits”, says the Managing Director.

SITEC puts its trust in particular in its motivated and competent employees who are more than capable of exploiting the full performance potential of the high-tech machining centres.

The majority of its demanding customers come from the field of the car and commercial vehicle industry – for example ZF Friedrichshafen one of the industry’s most reputable suppliers. This cooperation is manifested in a close competence partnership. Meanwhile around half the orders processed by SITEC come from this key player in the branch. “We produce the housings for the Ecomid truck transmission from ZF, for example”, says Ulrich Sigloch, giving us a little insight into the product portfolio. In this field, the company is in fact the exclusive supplier of ZF. The Managing Director also looks back on a relationship with this customer that has become established over time: “The number of orders we received from ZF has increased progressively over time, thanks certainly to our quality and supplier philosophy.” The processing of customer orders is clearly structured. “Weekly schedules determine our delivery dates and quality regulations require that we measure the parts at regular intervals”, is how Ulrich Sigloch describes the production processes.

Intelligent machine solution for more productivity

With its patented wheel magazine the DMC 60 H linear has a tool magazine for 40 tools even in its standard version, when equipped with five of these wheel magazines the machine can hold up to 303 tools.

The strict specifications in production explain why Ulrich Sigloch takes such a progressive approach in the name of his company where production technologies are concerned. The latest acquisition made by SITEC is a clear example of how productivity can be increased sustainably with an intelligent machine solution – in this case with the DMC 60 H linear from DMG MORI. SITEC has now managed to fit five of the compact horizontal machining centres into the same space where only four machining centres had room before. The trick here: the two companies put their heads together and came up with the solution of placing the cooling units on an overhead platform so that the new machines could be installed side-by-side despite the cramped conditions. This meant that the compact horizontal centres, with their width of just 2.5 meters, could be moved even closer together without interfering with access to their controls and tool magazines. The smaller machines present no problem for SITEC, either, as far as the size of the components is concerned: “We have developed our own clamping devices in order to make ideal use of the work area”, says Ulrich Sigloch about the in-house clamping construction.

Together with the integrated clamping hydraulics, the production network enables significant streamlining of the manufacturing process as the Managing Director explains: “Its automatic clamping saves us two minutes for every setup operation. This together with the short distances and optimised logistics means we only need two employees per shift to man the machines where we would otherwise have had to schedule a third operator.” The five machines have been running highly efficiently from the very outset, are operated meanwhile in a three-shift system at full capacity alone for the Ecomid housings, whereby Ulrich Sigloch goes on to tell us: “We still have to respond flexibly, because we produce two to three types of housings, each in up to eight different versions.”

Innovative technologies even in the standard version

The coolant units were place on an overhead platform so all the new machines could be installed side-by-side despite the cramped conditions. This meant that the compact horizontal centres could be moved even closer together without interfering with access to their controls and tool magazines.

Technologically speaking the five DMC 60 H linear centres also come up trumps at SITEC. Ulrich Sigloch goes on to talk about their geometric accuracy: “The direct drives in particular really come into their own with regard to our extremely tight dimensional shape and positional tolerances.” Expressed in figures: the machines have a circular and positioning accuracy of 4 µm and a repeatability accuracy of 3 µm. This adds up to a gain in accuracy of 25 percent compared to machines with ball screw spindles. The high level of reliability is another outstanding feature of the linear technology. “The maintenance costs for these drives are minimal and DMG MORI grants a five-year warranty – now that really is convincing.” Another point that benefits accuracy is the ingenious cooling of the machine. This encompasses all primary and secondary sections of the linear drives as well as the NC rotary table and the main spindle. In addition, the linear drives of the DMC 60 H linear – in combination with the extremely rigid, V-shaped and weight-optimised travelling column made of GGG60 – guarantee the necessary dynamics, even in highly productive 5-axis simultaneous machining. Acceleration here is up to 1 g, the rapid traverse up to 100 m/min.

The Managing Direction also praises the new magazine technology. “The wheel magazine is the perfect tooling solution for us: intelligent, fast and extremely compact.” With its patented wheel magazine the DMC 60 H linear has a tool magazine with space for 40 tools even in its standard version, when equipped with five of these wheel magazines the machine can hold up to 303 tools.
The machine can also be setup parallel to production and idle times already in the two wheel magazine version. The magazine also excels during operation: 2.5-second chip-to-chip times and delivery of the tool furthest away in just 5.6 seconds.

Production reliability thanks to fast service

Compared to ball screw spindles the DMC 60 H linear not only offers high dynamics but also a gain in accuracy of 25 percent as well. Circular and positioning accuracy, for example, are 4 µm and it has a repeatability accuracy of 3 µm.

SITEC continues the cooperation with DMG MORI even after the acquisition of the five DMC 60 H linear machines – not least where service is concerned. “The utilisation rate of the machines is so high that a breakdown of one or even two machining centres would have a great impact on our agreed delivery times”, says Ulrich Sigloch. So the service team must respond with the necessary speed whenever required. In this respect, he is extremely optimistic: “The excellent experience we have made with DMG MORI to date means we have no worries at all where service is concerned.”