Remarkable impressions thanks to perfect profile

Highest level of precision and process reliability guaranteed

Karl Wenk GmbH has been producing a wide range of rollers for over 90 years. The company specialises in printing and embossing rollers and develops surface finish designs and engraved finishes. When they needed an extremely smooth profile on a four-metre-long embossing roller for the glass industry, the experts from Lörrach-Brombach turned to Hommel+Keller Präzisionswerkzeuge GmbH, the global market leader in knurling technology based in Aldingen, and came away with a cut knurling tool perfect for the application that provides maximum precision right up to the profile points.

Embossing rollers are used in many industries to transfer surface finishes to various materials including plastic, aluminium, paper, cardboard, leather or even glass and then process them. The strengths of Karl Wenk GmbH lie in their customised solutions for the most varied of requirements. To meet the high demands of users and their own uncompromising quality standards, the traditional company is based on a combination of precise workmanship and cutting-edge production technologies. "We always want to offer our customers the best solutions – that is why we are always on the lookout for new technologies. At the recommendation of Hengst-Kessler GmbH, Mr. Reinhold Dreher from Hommel+Keller Präzisionswerkzeuge GmbH visited us to present the company's knurling technology. Both he and the technical possibilities made such a positive impression that we immediately contacted the company for this project, which involves profiling an embossing roller measuring 4,000 mm in length and with an outer diameter of 200 mm for a customer from the glass industry", says Peter Treichel, project and construction manager at Karl Wenk GmbH.

Matching high requirements

In addition to the dimensions of the roller, there were a variety of other specific characteristics that the knurling experts had to take into consideration for this project. The finished roller is intended to emboss the profile onto glass heated up to 1,200°C. The roller is therefore made of particularly high-quality stainless steel to withstand these high temperatures. The special centrifugal casting process used to produce the roller ensures a very clean and highly compressed structure – perfect for embossing but difficult to machine. Another requirement was the highest level of precision. The cylindrical concentricity could have a maximum tolerance of only 0.015 mm along the entire length of the roller. The knurling profile and the depth of the knurl also had to be uniform all over.

As Reinhold Dreher, application engineer at Hommel+Keller Präzisionswerkzeuge GmbH explains: "Owing to the high requirements for the profile, only a customised knurling tool was worth considering. The knurling process makes it possible to achieve maximum precision and outstanding surface qualities. The basis for this special variant was the zeus knurling tool 241, which we adjusted precisely to the application and the large machining diameter".

An ingenious tool for the perfect profile

The tool ensures the highest level of process reliability. The toothed serration between the 32 x 32 mm tool holder and the knurling head reduces vibrations to a minimum, thus guaranteeing maximum stability and extreme precision. The knurling head can be precisely positioned using setting gearing. This simplifies the process for setting up the equipment considerably and enables repeatable processes. The stable construction also ensures optimal tool positioning on the work piece. To achieve a perfectly formed profile and a uniform knurling depth, the user can finely adjust the knurling head quickly and easily using an adjusting spindle. 

"The production of the high-quality RGE profile swivelled at 30° entails two AA knurling wheels, both with a diameter of 42 mm and a knurling width of 13 mm. We have precisely adjusted the knurling wheels to the diameter of the roller to achieve a perfect profile. A special surface hardening method reduces the wear on the knurling wheels", says Reinhold Dreher. The highest level of precision and process reliability during tool changes is guaranteed thanks to the customised and precise positioning of the knurling wheel and the wheel mounting unit.

Quality control passed with flying colours

At Wenk, the perfect implementation of a project and absolute customer satisfaction is a top priority. This is why quality control plays a significant role in the processes. This includes inspecting the embossing using a sample from the roller, determining the profile depth using state-of-the-art technology and checking the roller for concentricity and an intact surface. The roller with the customised zeus knurling tool received a glowing report. "We have acquired a reliable, high precision tool that is also easy to use. Furthermore, the professional support we received from Hommel+Keller Präzisionswerkzeuge GmbH was excellent and the project went without a hitch. These are all good foundations for further cooperation on other projects in the future," says Peter Treichel.