Mandrel bar machining is no job for the faint of heart: if something goes wrong on a 25-metre long workpiece, that's tonnes of material fit for the recycling centre. GeisslerWista GmbH in Witten - an expert in mandrel bars - has no fear when it comes to facing such challenges, and is enjoying greater productivity and reliability thanks to process optimisation with tools and the expertise of CERATIZIT.
Hot-rolled seamless tubes are indispensable in sectors such as the energy and automotive industries. These are produced with high-quality mandrel bars, which serve to roll out a pre-pierced steel billet into a hollow from which the tube is finally manufactured. The loads acting on the mandrel bar are extreme, which is why both the material properties and the dimensional accuracy must be perfectly matched. This task requires extensive expertise together with perfectly interconnecting processes - and is just the job for the experts at GeisslerWista GmbH in Witten.
"When we peel mandrel bars up to 25 metres in length, we realise dimensional tolerances of no more than 0.05 millimetres. However, we can only do so if all processes are utilised to their fullest effect and are completely reliable. This requires that our machine technology, tools and operators engage with each other perfectly," explains Pascal Richter, production management, operations and maintenance manager at GeisslerWista GmbH.
When selecting a large peeling machine, GeisslerWista GmbH opted for a model from an American manufacturer. "Admittedly, this brand is a rare sight in German production halls, but it has certainly proven its worth for us," says Pascal Richter, who himself worked for well-known German manufacturer of peeling machines SMS Meer, and learnt the highly specialised profession from the ground up. This is how he encountered CERATIZIT tools for the first time, even before joining the GMH Group (to which GeisslerWista GmbH belongs) - and it was not to be the last time.
And so it was that Frank Klostermann, Technical Consulting & Sales/Cutting Tools at CERATIZIT, arrived at GeisslerWista in mid-2019 with the key task of increasing chip removal and giving the entire process an added turbo boost. "This is not the kind of problem for which you have an off-the-peg solution to hand. After all, the peeling machine is an exotic find that occurs only twice in Germany and it poses specific challenges for the tools," recalls Frank Klostermann.
Numerous tests were performed, because - as Pascal Richter and Frank Klostermann both agree - "it's pointless to conduct testing once and then leave it at that. Every blank is different, so whether it works or not is down to good or bad luck. When it comes to ensuring process security, systematic test runs are the best solution!" Two CERATIZIT employees also came to GeisslerWista to assist with this: Markus Bösing, application engineer from Kempten whose work focuses on peeling, and Peter Hohlrieder, peeling application manager from Reutte. "That allowed us to cover two production shifts over several days. Pascal Richter gave us plenty of time and freedom to try things out - and it shows in the end result!" says Frank Klostermann.
As a rule, it is necessary to run through several process cycles during the pre-peeling stage, depending on the diameter of the raw material and the maximum chip reduction. Firstly, it was remarkable that the CERATIZIT inserts were able to deliver greater chip reduction for the first time ever. But this was not enough for all those involved, because aside from the pure tool performance, Pascal Richter and the CERATIZIT engineers still saw further potential across the entire process. "Once you've fine-tuned the peeling process to its fullest extent, you need to look elsewhere. And so together we came up with the idea of optimising - or even eliminating - the changeover cycle from pre-peeling to finishing peeling!"
In order to deliver new developments to GeisslerWista at the earliest opportunity, Frank Klostermann initiated the testing of the new high-end cutting insert grade CTCP605 from CERATIZIT on the "small" peeling machine, which was currently undergoing set-up. The grade is specially adapted to bar peeling and impresses with outstanding performance when it comes to tool life, bar surface quality and roundness. High process security and maximum chip removal rates are among the outstanding features of these innovative indexable inserts. "We first used the new M48 chip breaker. With this combination, the cutting forces are reduced and the system is therefore subject to significantly less stress. However, in order to obtain even more meaningful performance data, we also compared the CTCP605 and CTCP615 grades and the difference between the M48 or M50 chip breaker - in other words we cross-compared everything," says Frank Klostermann.
Machining the workpieces on the small system involves a number of subsequent work steps, such as grinding or hardening. "This requires that the material achieve a specific roundness, corrugation and straightness. After all it's the first process in the sequence, so the better its execution, the fewer issues we have at the end. And it was with this optimisation assignment that we fired the starting signal for CERATIZIT to enter the race," reveals Pascal Richter.
The CERATIZIT tools should win the day once again - not least thanks to the help of the machine operators. After all, they are the ones who test and document the tools and parameters over a longer period of time. "It's very important to us that the employees have the freedom to give something a try, even at the risk of something going wrong. Ultimately, everyone benefits from optimised results," says Pascal Richter with conviction. And Frank Klostermann confirms: "We are satisfied when the employees enjoy working with our tools and achieve the best possible results with them. And that works best when you are also able to perform extensive testing, which is what happened at GeisslerWista." And so the cutting inserts in the new CTCP605 grade are now also part of the SMS 100's permanent equipment.
"What stands out when working with CERATIZIT - the entire approach is highly technical. You don't deal with sales teams who have no understanding of their products. On the contrary, we speak the same language, which makes the work very straightforward and ultimately leads to outstanding results very quickly," says Pascal Richter. This is largely thanks to the in-depth analysis of the test results obtained. Over the past few years, Frank Klostermann has built up a vast database containing a wide variety of machines, materials and tool combinations: "This allows us to generate initial solutions for the majority of problems, which we then optimise during the series of tests. We've been able to crack many a tough manufacturing nut with our project engineering team in this way!"
For 2021, Pascal Richter and his maintenance team will be upgrading a further system for operation as a customised GeisslerWista system: "We have made both design and programming changes to this end. If that goes well, we want to transfer it to the big peeling plant." No easy task, but Pascal Richter is confident that his young team is in a good position to manage that, too. And when it comes to tools? "We have complete faith in CERATIZIT and we're looking forward to seeing how the innovations prove their worth in continuous operation," sums up Pascal Richter.
Because things are also happening here - as confirmed by Frank Klostermann: "Until now, the RNGH38 button inserts were used as scorers, but we want to replace them with the new HNMJ13, which is smaller, double-sided and therefore more economical. Why are we doing this? So that the customer has even more options - because they can still revert back to the old inserts at any time too, if that's the preferred choice." The next step is to test a few more prototypes with quick-release fasteners, which allow the inserts to be changed directly in the machine. If these are well received then other customers will benefit from them too, because they will then be included in CERATIZIT's standard range.