A new, additively manufactured injection mold proved difficult to machine. The hard machining tool previously preferred by the toolmaking department of Erich Rothe GmbH & Co. KG broke after just five minutes. The attempt with a new tool was worthwhile: Using the milling tool HC643FB from Hufschmied Zerspanungssysteme, the finishing of the injection mold part made from Uddeholm Tyrax ESR turned out to be a process-safe solution.
Reducing cycle time in injection molding has always been an important optimization goal in plastic processing. "For the injection molding tool for the spools on which component belts are delivered in electronics manufacturing, we tested various variants of the standard steel insert. Then we decided to try contour-adjacent cooling," explains Bernd Gruber, head of toolmaking at Rothe. Gruber found a service provider who could manufacture his new design using the Laser Powder Bed Fusion (LPBF) process with Uddeholm Tyrax ESR, a corrosion-resistant premium plastic mold steel with high ductility, wear resistance, and a hardness of 58 HRC. Additively manufactured workpieces always show their layer-wise production, and the rough surface needs to be post-processed. This became a challenge in this case.
Alternative Tool
"We oriented ourselves to the specifications of the material supplier when finishing the blank, but the result was frustrating. The tool's cutting edges broke after five minutes," recalls Max Hahn, the CNC technician who wanted to bring the blank into its final shape on a Micron HEM 500U. An offer from Hufschmied came at the right time and provided the solution with a tool life of at least 18 hours. HC643FB is a 3D finishing cutter for hard machining over 40 HRC and up to 72 HRC. It features three unevenly divided cutting edges and the contour of a flattened sphere, allowing for 35 percent more engagement than a ball cutter.
The tool is made of an ultra-fine grain carbide substrate and features a special micro-edge geometry. The in-house 3 µm thick TL12 coating made of TiAlSi has a hardness of 3800 HV.
Suitable for this material
For the special tool steel from Voestalpine, the hard machining tool from Hufschmied proved to be the perfect choice. "We examined one of the Hufschmied tools under the microscope after 15 hours of use, and it looked as good as new," recalls Max Hahn. The tool life ultimately reached at least 18 hours. "We greatly appreciate that the hard machining tools from Hufschmied provide us with this process reliability," says Bernd Gruber.
Thomas Wohlfromm, Technical Consultant and Sales Representative at Hufschmied Zerspanungssysteme GmbH, is pleased about the now regular orders from Rothe: "We are much better known for our tools for machining composite materials."
I am even more pleased that we have encountered a challenge related to a hard material for additive manufacturing and have successfully overcome it. Finishing such blanks is a task that many users will still face, and it is good to know that we already have the solution.
Contact:
