With the right tools and state-of-the-art CAM software, toolmakers and mould makers can keep their production capacity flexible, and will be able to ramp it up by up to 85 percent once the economy picks up again. Article by Michael Knauer, Hoffmann Group.
Toolmakers and mould makers are amongst the companies keeping a firm handle on the impact of the coronavirus pandemic. Many companies are asking themselves how they can weather the storm unscathed as far as possible and adapt their capacity quickly once the market improves. This has placed the spotlight on production methods such as ‘circle-segment milling’, also known as ‘Parabolic Performance Cutting (PPC)’ or ‘barrel milling’.
PPC tools enable the finishing work for a tool mould to be completed up to nine times faster or, alternatively, the surface quality to be improved up to 80-fold. For example, Koller Formenbau GmbH has used PPC milling cutters supplied by the Hoffmann Group to reduce the finish machining time for geometrically defined surfaces from 100 hours to 15 hours. The PPC method is also ideally suited to finish machining work on 3D-printed parts.
On PPC tools, the main cutting edge on the milling cutters is curved. Compared against a classic ball-nosed slot drill where the effective radius is half the tool diameter, PPC tools have a much larger effective radius, up to 1,000 millimetres, thus permitting a significantly larger engagement length on the workpiece. However, their more complex geometry means they place higher demands on the CAM software. The software not only needs to offer the ‘circle-segment milling’ strategy, it must also have a tooling database which holds the exact geometries of the PPC tools. What’s more, since the tools are aligned obliquely to the workpiece, the method can only be employed in conjunction with a 5-axis milling machine. Not all 5 axes need to be in use here. Often, once the tool has been set up, the draft angles can also be finished with 1 to 2 axes clamped. It may also be possible for flat faces and freely accessible surfaces with no interfering contours to be machined on a 3-axis machine. In the past there were only a few software programs that offered the ‘circle-segment milling’ functionality. However, that is no longer the case. Koller Formenbau, for instance, already used a 5-axis machine and the Hypermill software, so they only needed the right tool. At reasonable expense, the company was able to boost productivity by up to 85 percent, thereby increasing its capacity without having to procure a new machine.
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