In grinding operations, productivity and component quality are not determined by the machine alone. The preparation of the coolant lubricant (KSS) also plays a significant role in success. The capabilities of the new hydrostatic filter generation from KNOLL Maschinenbau are demonstrated by the installation of a HydroPur H 1000 on a Junker JUMAT 6S at the drive manufacturer SEW-EURODRIVE.
SEW-EURODRIVE is a globally active provider of drive and automation technology. The company's headquarters is located in Bruchsal, where the large gear manufacturing plant is also situated. As the name suggests, gear units weighing up to 22 tons are developed and produced there for demanding industrial applications. These are used in conveyor technology, the raw materials industry, port handling, the steel industry, and many other areas.
A key strength of SEW-EURODRIVE is – in addition to the extensive gearbox expertise developed over more than 90 years – the fast delivery capability, which ranges from one to fifteen days depending on the requirements. SEW-EURODRIVE achieves this short timeframe through a sophisticated modular system. Depending on the customer's specifications regarding torque, speed, and maximum housing size, the drive specialists can often assemble a custom gearbox from this system.
To be able to respond flexibly and quickly to special requests, the depth of production is high. Markus Grimm, responsible for investments in machine tools and automation solutions at the large gear factory in Bruchsal, explains: "Our machine park includes all types of machining machines: for turning, milling, grinding, gear cutting, etc. We have a straightening press and a hardening shop, so basically, we only need to purchase screws, seals, and bearings."
Increased productivity with a new grinding machine
His responsibilities include the procurement of new machines and systems, as well as the optimization of existing manufacturing processes. "We continuously invest in the modernization of our production to further improve quality, productivity, and sustainability," emphasizes Grimm.
The starting point of the project described here was a replacement investment in 2021: An external cylindrical grinding machine had to be replaced due to its age and increased maintenance effort. Markus Grimm and his colleagues decided to acquire a JUMAT 6S from Erwin Junker Maschinenfabrik GmbH, Nordrach. "Through simultaneous processing and modern grinding technology, this machine significantly reduces processing times compared to the previous machine," argues Grimm. "Additionally, the automated operation contributes to increased productivity."
At JUMAT 6S, SEW-EURODRIVE primarily processes shaft-shaped gearbox components – especially output and drive shafts. The outer diameters for bearing seats are ground with the highest precision and surface quality, and in some cases, the flat surfaces are also ground. In most cases, the shafts are made of heat-treated steel C60 or comparable unhardened steel grades. Ceramic-bonded CBN wheels are used as the grinding medium.
High demands on the coolant preparation
An important component of the entire grinding process is the coolant lubricant emulsion and its preparation. The filtration system must be capable of continuously supplying the grinding process with clean and temperature-stable coolant lubricant to ensure that the machining can proceed reliably and automatically. Following the recommendation of the machine manufacturer, the responsible parties decided to equip the JUMAT 6S with a hydrostatic filter HL 650 from KNOLL.
"We have known KNOLL for many years, during which the company has equipped numerous our machine tools with filtration and conveying technology. Therefore, a trusting business relationship has existed for a long time. A key point in our decision for KNOLL was ultimately the overall technical concept and the willingness to further develop the solution in application-oriented collaboration with us."
Increasing material removal performance becomes a challenge.
With the performance of the Junker JUMAT 6S and the continuous optimization of the grinding process, the material removal rate increased noticeably – along with it, the amount of fine grinding sludge introduced into the emulsion. This posed an increasing challenge for the KNOLL Hydrostatfilter HL 650. Although it still met the required filtration performance and coolant quality, the consumption of filter fleece increased significantly. Changing the fleece roll became necessary up to once a day, which resulted in high operating material costs and corresponding maintenance efforts.
To improve this, SEW-EURODRIVE and KNOLL jointly analyzed the process conditions. The result: To make filtration more efficient, stable, and economical, KNOLL proposed to retrofit the filtration system to the new Hydrostat filter HydroPur H 1000 as part of a field test. "This is how we envision a partnership," says Markus Grimm. "Recognizing the problem together and offering a solution. Of course, we agreed."
New development ensures greater process reserve and lower energy consumption.
Since the beginning of 2025, SEW-EURODRIVE has been using the HydroPur H 1000 on the JUMAT 6S. KNOLL product manager Jannik Nörz explains: "Unlike the hydrostatic filter HL, our HydroPur filter systems are completely modular in design. This starts with the filter top, which is available in four different sizes and corresponding maximum filter capacities." To further develop the existing filter system to match the increased performance of the grinding machine and provide more process reserve, the decision-makers opted for the HydroPur H 1000, whose filter capacity for emulsion is 1000 l/min with a fleece width of 1,520 mm. The filter area has increased more than fourfold compared to the previous solution to 0.608 m². This gives the system significantly more reserve for the high dirt input from the grinding process.
In addition, the HydroPur H 1000 scores points against the previous HL 650 in terms of energy balance: While the filter top of the HL 650 consumed 1.75 kWh per operating hour, the filter top of the new HydroPur H 1000 requires only 0.85 kWh, which is just under half. The HydroPur H 1000 also saves energy in circulation operation: its consumption is 3.36 kWh per operating hour. This is about one third less energy than the HL 650, which consumes 5.125 kWh. This is due in part to the new, simpler design of the filter chamber, and on the other hand, a reduced fleece drive, as the fleece roll operates at longer intervals.
Successful conversion of the filter system
The filter module HydroPur H 1000 could be mounted on the existing tank with an adapter. The new system concept allowed for further improvements, such as the addition of a degassing channel and a frequency-controlled lifting pump. Both counteract foam formation, which had repeatedly caused problems in earlier grinding operations. During the field test, KNOLL also integrated an optionally available winding unit for the used filter fleece, which separates the dirt discharge and thus contributes to more cost-effective disposal.
KNOLL product manager Jannik Nörz adds: 'The modularity continues with numerous options that allow us to configure the filter exactly to the requirements of the users. For example, a magnetic roller for pre-separation, vacuum support, and a continuous belt are available. All standardized functional modules can also be added later.'
Vacuum support brings many advantages
Jannik Nörz does not want to leave out a technical highlight: 'Through vacuum support and a higher differential pressure at the filter surface, the KSS flow rate increases, and a homogeneous filter cake is built up faster, which carries away the finest particles. The user benefits from purer coolant, which positively affects workpiece quality and tool life.'
In addition, the vacuum support reduces the consumption of filter fleece.
'With the new HydroPur, we only need to change the fleece every two weeks in two-layer operation,' mentions Markus Grimm. 'Nevertheless, we are currently examining the possibility of switching from filter fleece to the optionally available continuous belt with fabric cleaning. This would reduce the consumables as well as operating and disposal costs to almost zero. And it would be another contribution to sustainable production.'
Partnership on equal terms
For Markus Grimm and his colleagues from production, the switch to the KNOLL Hydrostat filter HydroPur H 1000 is a complete success, as the filter system masters the high removal performance of the JUMAT 6S and ensures maximum production safety. 'With the HydroPur filter top, the larger effective filter area, the degassing channel, and the frequency-controlled lifting pump, the existing system has been specifically further developed,' Grimm is pleased.
'We were able to continue using the existing infrastructure while significantly increasing the filtration capability.'
The SEW-EURODRIVE team around Markus Grimm evaluates the collaboration with KNOLL positively: 'Both during installation and during further optimization, open communication, structured processing, and reliable technical support ensured a smooth process.' Even in ongoing operations, the paths are short and the contacts are competent – an important factor for SEW-EURODRIVE. Grimm's conclusion: 'KNOLL accompanies us not only as a supplier but as a technical partner – a role that enables further joint development work on economical and sustainable manufacturing solutions.'
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