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TM Precision Mechanical Production GmbH in Slovakia

Maximum Precision for Rotor Shafts

The latest washing machines are so quiet that they could even be placed in the living room. This is thanks, in part, to high-precision motor shafts – the specialty of TM Precision Mechanical Production GmbH, a Slovakian company that places its trust in JUNKER’s expertise and JUPITER grinding machine.

In the far east of Slovakia lies the small town of Michalovce, which is home to TM Precision Mechanical Production GmbH. The company’s main customers are German brand manufacturers. “Our customers are technology leaders in the field of ‚white goods‘ – and they want to stay that way”, explains Production Manager Milan Kadilak. “The level of quality required in this industry has risen enormously. “With JUNKER, we have a partner who is ready and able to supply the latest grinding technology and to implement extremely complex requirements themselves.”

Every micron counts

Behind the deceptively simple rotor shafts lies a huge manufacturing challenge. The small components must be processed with absolute precision to ensure the washing machines are whisper-quiet. To achieve FFT quality, a roundness of less than one µ for the bearing diameters was reached. The workpieces also fulfilled the need for minimal undulation. High output, reliable processes and consistent quality from start to finish are also essential.

Thus, a grinding machine that delivers precision results and high output was needed. Which is why Milan Kadilak turned to JUNKER’s expertise and grinding machines. “The needs of a market leader are best met with the knowledge and machines of another market leader,” says Milan Kadilak with conviction.

High standards right from the start

Before the project started, the customer’s needs and production conditions were analyzed in detail. With the JUPITER, a specialist machine for centerless cylindrical grinding, JUNKER has provided the Slovakian company with the right grinding machine for the tasks at hand. JUNKER’s service concept covers the custom configuration of the machine, notably the setup for the grinding process in question. Ultimately, first-class components are essential where top quality end products are concerned.

So when it came to setting up the grinding process, the main task for the experts from JUNKER was to ensure that the produced parts met the extremely high precision and quality standards of the rotor shaft manufacturer – consistent quality day after day, without even the smallest deviation in the roundness of the workpiece.

Quality criteria: workpiece roundness and waviness

There are three key aspects which affect the roundness of the workpiece during centerless grinding: the grinding gap geometry, the machine parameters and the rigidity of the grinding gap components. Excellent quality, and thus, outstanding products, can only be achieved when all three factors are in perfect harmony.

The JUPITER series is an accumulation of more than 55 years of experience in centerless grinding at JUNKER. The high-precision machines also enable both straight plunge-cut grinding and inclined plunge-cut grinding with throughfeed grinding. Automatic setting of the grinding gap geometry optimizes the grinding process and the inclined bed guarantees maximum dimensional accuracy.

High output, short changeover times

The JUPITER machine enables the Slovakian manufacturer to produce three rotor shafts per minute using centerless grinding. As there is no center point, this grinding process is unbeatably fast, resulting in high output during series production. The machine also has numerous features, which make setup and changeover easier, such as the patented CNC height adjustment of the support rail. Thus, in comparison to conventional machines for centerless cylindrical grinding, the JUPITER considerably reduces the time needed to produce the first workpiece.

“Easy changeover and short cycle times were decisive factors for us,” reports Milan Kadilak. The CNC dressing option provides huge added value for the company: some of the shaft types that the company produces only differ slightly in terms of design and geometry. With the JUPITER, changeover can be carried out through the software alone. There is no need to change the grinding wheels. As a result, the workpiece changeover only takes about 30 minutes.

Short grinding times, perfect results

However, speed and output are only two of the factors important to Milan Kadilak. Achieving the customer’s request for short cycle times while at the same time providing consistently high-precision grinding posed a challenge for the grinding experts at JUNKER. The configuration of the grinding wheel is decisive when it comes to consistently precise results. This was tested in a demanding yet successful grinding test before the order was placed.

JUNKER knows which grinding wheel specification is the most suitable for which material. This is why the experts at JUNKER adapt every grinding machine to suit the customer’s exact requirements. Although the requested combination of high output and maximum precision was a challenge, the experts at JUNKER were more than up to the task: “After intensive and demanding grinding tests at the JUNKER technology center, the optimum grinding wheel for machining rotor shafts was found,” says Milan Kadilak.

Interfaces for subsequent process optimization

One of the distinguishing features of JUNKER machines is their standardized interfaces. These can be used to incorporate either entire lines or individual machines into the production process, for transporting workpieces or for quality control, for example. This means that developed solutions can be easily extended and updated at any time – even after the machine commissioning.

This was also the case for the rotor shaft production in Michalovce. Once machining is complete, these are checked in a measuring station. After the JUPITER commissioning, this originally manual process, was then automated. To do so, a robot was integrated into the process chain via an interface: it picks up the finished shafts, transports them to a measuring station and then places them back on the exit conveyor.

More than a grinding machine

With the JUPITER centerless cylindrical grinding machine – and all other models – JUNKER has created more than just a machine. The performance promise from the grinding experts also includes the provision of high-precision grinding concepts, which are designed to meet the customer’s exact needs and production processes.

The JUPITER centerless cylindrical grinding machine from JUNKER delivers outstanding grinding quality thanks to market-leading rigidity. Depending on the application, corundum, CBN or diamond is used as an abrasive.

The centerless plunge-cut grinding method entails grinding workpieces with offset or profiled diameters.

During centerless cylindrical grinding, the workpiece is not clamped but lies in the grinding gap between the grinding wheel, regulating wheel and support rail. The grinding pressure presses the workpiece against the regulating wheel, which brakes the workpiece to its own peripheral speed.

The rotor shaft manufacturer’s workpieces are transferred automatically. The JUPITER has a customized measurement system for quality control.

The JUPITER produces a high output by machining three rotor shafts per minute with a centerless cylindrical grinding process.