Post processing? Not necessary
The basic structure of many branded sports seats comes from REINERT Kunststofftechnik GmbH & Co. KG, a company of the leading automotive supplier AUNDE Group. The fact that the bucket seats had to be reworked by hand after machining was a weak point in the manufacturing process for a long time. The request to the tool manufacturer Hufschmied brought the solution.
REINERT manufactures bucket seats from glass fiber reinforced polyamide (PA6 with 47% glass fiber content). As good as the material is for this application, there was always a problem with the completion. The two millimeter thick blanks are given their final shape on a CNC milling center. Above all, a series of circular pockets and bores must be attached. However, the fiber composite material frayed at the edges, so that each of the around 45 seat shells produced annually had to be deburred by hand, which was a laborious process. Wouldn't it be possible to create better surfaces and reduce this effort? Martin Potyka, who is responsible for tool management at REINERT, found out through the internet that Hufschmied offers special tools for fiber composites as well as process advice and inquired there. Marvin Röhm, Technical Advisor at Hufschmied then left Bobingen near Augsburg on the way to Bissingen an der Teck to look at the case. “If you want to optimize milling processes, you have to consider and coordinate all aspects: workpiece, material, tool path, machine and tool,” explains Marvin Röhm.
bull's-eye
Martin Potyka and Marvin Röhm decided to start immediately with test machining on a POS Mill 3-axis CNC machine with a maximum speed of 10 revolutions per minute. The "T-Rex" tool from the sales representative's tool box was to be tested. It was driven at 000 rpm with a feed of 8 m. The pockets were plunged into the helical path and milled out in the opposite direction. The difference to the previous process was immediately apparent: smooth edges without delamination of the composite material. “The single-edged tool used to machine bucket seats might be a good choice for polyamide alone, but not for fiberglass-reinforced plastic. Our tool has four cutting edges with a special geometry with a pulling and pressing effect and roughing and finishing functions in one tool. In this way, we limit the development of heat and vibrations during processing,” explains Röhm.
The tested tool "T-Rex" was the right one and Martin Potyka only chose the model with a diameter of four millimeters instead of eight millimeters. Series production takes place on a DMG DMU CNC 5-axis machine. "We are from that Hufschmiedtool convinces,” says Martin Potyka. "It's impressive what surface quality we can now achieve and not only that: we save 40 percent processing time when milling - in addition to saving the complete manual deburring."
Diamond coating option
Hufschmied also offers the T-Rex milling tool with a microcrystalline diamond coating, since glass or carbon fibers have an abrasive effect on the cutting edges of the tool. If necessary, REINERT Kunststofftechnik will switch to this version if it pays off. The manufacturer is currently using the blank version of the patented tool for composites and is gaining experience with the tool life.