A team of two – for 9,000 hours of continuous operation

The first is blue and the second is white, but that's the only difference between the two Bumotec s191 machining centres from Starrag that have already proved their worth at the Hessen-based company Kroeplin, which specialises in dimension measurement. After the first, blue, Bumotec machine had been operating continuously for four years, the company decided to purchase another one with the same extras – this time in white. It was a wise decision; the two machines jointly guarantee 9,000 operating hours per year. 

    “This is one of the reasons why we needed a second Bumotec”, says Markus Deberle, Managing Director of Kroeplin GmbH, holding out a tiny metal component towards our photographer, Ralf Baumgarten. It’s the measuring contact tip of the smallest probe arm of an electronic probe, which measures lengths of between 2.5 and 12 mm. The supremely delicate component is made from stainless steel 1.4301, and is around 20 mm long. Its distinctive features include extremely small radii (0.4 and 0.1 mm) and a thickness of less than 0.8 mm in certain sections. This component makes it possible to examine grooves for hydraulic seals easily and accurately (to name but one example).

    In the past, it was manufactured using several different mechanical and manual procedures. According to Deberle; “The Bumotec means that we can mill a finished stainless steel component from a single piece of stainless steel bar, even during an unmanned shift, without the need for any manual labour at all”.

    The company uses a total of almost 20 machine tools both in Schlüchtern and at its second site in Mariánské Lázně (Czech Republic). This includes not only the two Bumotec machines but also four CNC lathes, four CNC milling machines, three horizontal machining centres and some specialist machines. “We originally chose the Bumotec because the medical technology parts manufactured on the machine were very similar to our components in terms of geometry and material”, recalls Deberle. “I was impressed by the wide range of components and the option of using a bar feeder. This made it possible for us to operate the machine during unstaffed shifts at night and at weekends”.

    A complete machining strategy allowed Kroeplin to reduce processing time and costs by at least 30% across the board.

    In 2013, the Managing Director decided to buy a Bumotec s191 milling and turning centre – in blue, as was standard back then. Choosing the right machine is absolutely vital for a medium-sized manufacturer. According to Deberle, “Basically, we select our machine tools according to what we want to be able to manufacture on them. The machines must be a good fit for the range of components that we currently produce and that we plan to produce in the future”. 

    “We can use the machine to manufacture extremely complex parts with a geometry that would overwhelm the capacities of other machines”.

    Michael Paulus, Regional Sales Manager at TechCenter Immendingen explains the situation in greater detail; “Mr Deberle rapidly realised that his high requirements closely matched the standards that apply in the field of medical technology”.   The tiny probe was previously manufactured using three different machines and manual work. A complete machining strategy allowed Kroeplin to reduce processing time and costs by at least 30% across the board. Deberle points out another added bonus, “We can use the machine to manufacture extremely complex parts with a geometry that would overwhelm the capacities of other machines”. To his surprise, he rapidly also discovered that the machine was very popular among his designers, since it gave them more freedom to develop significantly more complex components. “We’ve learnt something new with every new part”, says the Managing Director. “And that has meant a steady increase in the volume of orders”.

    Both the first machine and the second machine that was acquired at a later date are remarkable for the number of extra features they incorporate. Deberle opted for an identical setup with his second machine, since he wanted to leverage the full potential available once again. And so his order included linear-driven Y-and Z-axes, turning and milling functions, a counter spindle A, an extension allowing the tool magazine to hold 90 tools, a pneumatic bar feeding system and interfaces with the FMB bar feeders, enabling fully automated operation during unmanned shifts. Extra features include fire extinguishing equipment for both machines. According to Paulus; “This is mandatory in the EU if you’re machining parts during unmanned shifts using oil as a coolant”.  

    “The Bumotec means that we can mill a finished stainless steel component from a single piece of stainless steel bar, even during an unmanned shift, without the need for any manual labour at all.”

    One of the reasons for purchasing a second s191 was to incorporate a certain level of redundancy into the company’s processes. The strategy of using at least two machines with the same equipment, so that one can easily take over the work of the other, has proved a success. In some cases, the machines are not even located in the same country; for example, we operate identical turning machines with a main spindle and a counter spindle and a tool turret in both Schlüchtern and Mariánské Lázně. In the words of the Managing Director, “Now we’re applying the same approach with the Bumotec s191 – if one machine fails, the other can still continue manufacturing parts. Since both operate with a Fanuc 34i controller, we’ve been able to use our existing programs for the new machine; there’s been no need for a new post processor or for any retraining of the operators”.

    The measuring contact tip of a tiny electronic probe arm is one of the reasons why Kroeplin needed a second Bumotec.

    An additional factor in the decision was that the first Bumotec s191 was being operated for 7,200 hours per year, which was an excessive utilisation rate given that the total number of operating hours in a year is only around 8,000. “There was hardly any time left for maintenance and servicing”, says Deberle. “The number of parts manufactured using this machine has increased yet further, because our designers are taking advantage of the freedom available to them to work on more complex parts”.

    The order confirmation for the second Bumotec s191 contains one very important sentence; “The ideal ambient temperature is between 18 and 22 degrees Celsius”. Kroeplin complies with this specification not by means of an expensive air-conditioning system, but by using a smarter solution that saves money and protects the environment. According to Deberle, “We don’t cool the machine from the exterior; instead, we selectively dissipate the heat within its interior”.

    Whenever we investigate a Starrag success story, there’s always one key question we ask; to what extent does the Starrag machine deliver on our claim of “Engineering precisely what you value”? Deberle doesn’t have any facts and figures to hand, but he could not be happier with his twin team of machines. He says that another point in favour of the ‘team of two’ is the close relationship that has formed between Volker Lorenz, the main operator and programmer and Jan Wolf, from Bumotec Service, who always provides rapid and expert responses to any queries. And what does a managing director dream about achieving in the future, when he has already achieved so much in the past? Deberle fires back an answer straight away, without needing any time to think about it, “A robot carrying out fully automated measurements with a Kroeplin measuring instrument in its hand”.  There seems little doubt that the improved measuring contact tips that would be required for this purpose will still be manufactured in a clamping device on one of the two Bumotec machines.