- ROEMHELD: Clamping filigree printing machine components on a grinding machine without deformation
- Specialist develops application-specific clamping solution for high-precision grinding at Heidelberger Druckmaschinen
Hilchenbach, November 12, 2018. The clamping technology manufacturer ROEMHELD has developed a high-precision clamping and centring system for grinding particularly filigree printing machine components. The application-specific solution is based on HILMA machine vices of the new MC-P series. It can be used to machine the surfaces of unstable workpieces in the Brandenburg plant of Heidelberger Druckmaschinen AG (Heidelberg) with particularly low deformation.
Heidelberg can even undercut the tolerance specification of producing a flatness of less than 10 μm. The maximum flatness deviation is certainly within the tolerance requirement and thus far below the values achieved by the machine manufacturer with clamping devices from other manufacturers. "We are very satisfied with this clamping system and produce the highest quality for our application," praises Daniel Böttger from the Tool and Machine Technology Department at Heidelberg. In the run-up to the project, the company had long searched for a suitable clamping technology for the grinding application.
For fine grinding, a slim component must be clamped, which is extremely unstable due to its length of 500 mm at a depth of only 12 mm and a width of 90 mm. The workpiece made of an iron-nickel alloy is milled, drilled and pre-ground in advance. A few years ago, the Brandenburg production site took over production to expand its know-how and to be able to guarantee the quality of the workpieces at all times. "We are constantly taking on new production challenges," explains Böttger, "and are working consistently to achieve the perfect result.”
In advance, the Brandenburg company had sought support from various clamping technology manufacturers, who, however, did not provide any useful solutions for the process. "The results were always unsatisfactory," says Böttger. Finally, the company developed its own clamping fixture, with which it achieved better results. However, the rate of rejection was still at an unacceptable level. "The component lay flat, was clamped, ground and then released - and was warped," he reports. To reduce scrap, half of the workpieces had to be reworked very laboriously and cost-intensively.
Products from the ROEMHELD Group's clamping technology range have been used successfully for many years in milling operations in the factory. "But when it came to these sensitive grinding issues, we didn't first look at Hilma-Römheld as a possible problem solver," Böttger reports. This changed at the end of 2016: at that time was the first contact between Daniel Böttger and Christoph Neuhaus, Product Manager Workpiece Clamping Systems at Hilma-Römheld GmbH in Hilchenbach, North Rhine-Westphalia.
"We have a very large assortment, the total range of the ROEMHELD Group comprises more than 20,000 articles. If nobody else has a solution, we'll find it," says Neuhaus confidently. "Even if we don't make any progress with standard clamping devices, we can help, because one of our core competencies is the development of systems for individual applications.”
Based on the HILMA MC-P machine vice, which is available in versions for position flexible and concentric clamping, the ROEMHELD designers developed a suitable clamping solution by means of extensive tests. "Our goal was to get the most out of this element, which was originally developed for machining centres," reports the product manager.
In the concentric clamping version, two mechanically connected clamping slides travel together to the centre of the clamping system. Since the clamping spindle is mounted high up in the housing, deformation of the component is reduced to a minimum.
The clamping point of the position flexible machine vices is floating with released locking. Here, too, the clamping slides first approach the workpiece concentrically. If the first clamping jaw has contact with the component, the second clamping jaw is moved until both are correctly positioned. The desired clamping force is then applied with the torque wrench and the clamping point is fixed via a clamping spindle. Thus, it can be adapted exactly to the position of the workpiece.
After a combination of three concentric clamping vices with 100 mm jaw width had not yet achieved the desired result, the clamping technology specialists tested a more complex variant consisting of five elements: A concentric vice in the middle clamps the workpiece first, then it is clamped on the right and left with two position flexible vices and subsequently locked. For higher clamping accuracy, extra-flat clamping jaws with a width of 60 mm each are used, which the company has specially manufactured for this application.
"Our internal tests worked very well," says Neuhaus, "so we were able to make the clamping system available to the customer at the beginning of June 2017 for free testing under production conditions.” It was very well received and was finally ordered by the company in November. Thus, the great advance performance of design and technical sales has paid off for all parties involved.
Now the clamping technology experts are in the process of perfecting their complete solution. Newly developed clamping jaws with a special coating for greater grip are intended to further improve the machining result.
57271 Hilchenbach, Germany
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