High-Feed, High Accuracy & Tight Tolerances Milling

WXS-LN-EBD rib processing ball nose end mill demonstrates long tool life and superior accuracy in high-feed processing of metal rollers at 54 HRC

Magnus Hoyer  |  OSG Germany

A manufacturing process that involves the embossing of sheet metal stamping rollers in 1.2379 tool steel at a length of 80 mm. At first glance, the production of this component seems neither demanding nor difficult. The challenge, however, lies in the detail, which involves maintaining a tolerance of 0.01 mm and continuous machining of up to 24 hours. With the small diameter embossing, the cavities in the rollers are positioned tightly, which prevents the use of high-feed-rate as the milling machine does not have adequate room to accelerate or decelerate. As a result, the cutting tool for the job has to quickly grind through the short traverse paths with great precision. With the rollers being made out of high hardened materials at 54 HRC, an end mill with a sharp cutting edge would be the typical tooling choice. At least that was the experience for PräWeba Engraving and HSC Technology GmbH.

Established in 1996, PräWeba is a group of specialists for CNC production located in Bad Lauterberg, southern Harz, Germany. Lead by Managing Director Rolf Stilzebach, who has years of experience in the programming of part processing, PräWeba’s core services include engraving, tool making, forming and CAD services. PräWeba works with a wide variety of requirements, surfaces and materials, such as plastic, Plexiglas, brass, aluminum, stainless steel, and other metals up to a hardness of 65 HRC.

For more than two decades, PräWeba has supplied precision products for various renowned clients around the world for their industrial applications. PräWeba prides itself in its quality of work. The company places great emphasis on dimensional and detail accuracy. In metal manufacturing, even minimal inaccuracies in seemingly unimportant parts may add up in subsequent processes in such a way that the overall result is unacceptable. To guarantee absolute precision, PräWeba always manufactures products using modern CNC milling machines, high quality clamping systems and optimum cutting tools.

From left to right, PräWEBA Production Manager Sascha Wedemeyer, PräWEBA Managing Director Rolf Stilzebach and OSG Sales and Technical Specialist Nico Henze.

In the case of PräWeba’s metal roller production, which involves the machining of tightly packed cavities, the tolerances for the final product are in the micrometer range, where the tolerance of the embossing tool must lie within +/- 0.01 mm utilizing a cutter diameter between 0.4 and 0.8 mm.

Because the cavities in the metal stamping rollers are so tightly packed, PräWEBA sets its cutting parameters to approximately 90 percent value of OSG’s recommendation for the WXS-LN-EBD.

As tooling cost is factored into the cost of the overall production, which would be passed on to the client, PräWEBA is always particular with their tooling choice. PräWEBA welcomes new tooling solutions as long as significant improvements in cost efficiency can be achieved. The tooling that PräWEBA initially employed was fair. However, when compared with the WXS-LN-EBD, OSG is the obvious winner in both processing time and tool life.

The WXS-LN-EBD is a 2-flute, long-neck ball nose carbide end mill designed for high-feed milling of hardened steels up to 65 HRC and stainless steels. Equipped with OSG’s original WXS coating for superior heat and wear resistant, this rib processing end mill series is able to achieve optimal performance with high precision and efficiency under aggressive machining conditions.

WXS-LN-EBD - Type 1 - 001
The WXS-LN-EBD is a 2-flute, long-neck ball nose carbide end mill designed for high-feed milling of hardened steels up to 65 HRC and stainless steels.

PräWEBA was running their previous milling cutter at a speed of 13,000 rpm. In contrast, OSG’s WXS-LN-EBD ball nose end mill is capable of running at a speed of 18,000 rpm under identical cutting environment. Furthermore, every embossing roller would cause a great deal of wear on the cutting tool due to the metal’s high hardness at 54 HRC. PräWEBA’s previous tooling choice required 16 to 20 end mills per roller. With OSG’s WXS-LN-EBD, only six end mills are required per roller.

“We have tested, calculated and weighed up our alternatives,” said PräWEBA Managing Director Rolf Stilzebach. “The conclusion is that OSG’s WXS-LN-EBD is capable of running at higher feed rates and gives us approximately 20 to 30 percent longer tool life, saving us considerable tooling costs.”

After switching to OSG’s WXS-LN-EBD rib processing ball nose end mill, PräWEBA is able to increase tool life by an estimate of 125 percent in their production of metal stamping rollers.

As the WXS-LN-EBD is designed for highly efficient milling in applications involving hard metals, intricate details and smooth finishes, PräWEBA is using it for both semi-roughing and finishing processes to take full advantage of the tool’s dual capabilities.

Machining centers today are capable of following precise, complex tool paths at high feed rates. With the right tooling choice, even intricate parts that require high accuracy with tight tolerances can be processed at high feed rate to maximize cost efficiency.