HSC machining in the manufacture of molds for medical technology
In a joint project, GF Machining Solutions and Zecha are comparing four different automated manufacturing processes for injection molding – with a focus on their qualities and run times.
GF Machining Solutions production equipment and Zecha cutters open up four economical options with different surface finishes for implementing cavities in a mold insert in 1.2343 with a hardness of 52 HRC. The first manufacturing process to make a cavity is EDM using a graphite or copper electrode.
Production of injection molds using graphite electrodes
The complex production process consists of hard milling of the mold insert, electrode milling and subsequent die-sinking EDM. The process of producing an injection mold using a graphite electrode takes just under 57 minutes in total, but requires many work steps. With Zecha tools from the Seagull family on GF machines, the Mikron Mill S 600 U and Form X 600, users benefit from tolerances of ± 0.005 millimeters as well as surface qualities Ra 1.6 micrometers and VDI 24. The machine frame made of polymer concrete with high thermal inertia and good damping properties makes the Mikron Mill S series special. All five axes are equipped with direct drives (X, Y, Z, B, C drives) and thus enable rapid movements of up to 100 meters per minute and precise positioning to µ.
Thanks to a spindle with Opti Cool or Cool Core technology, the temperature management system consisting of independent cooling circuits ensures optimal cooling of all heat sources and the machine frame. Process reliability, productivity and part accuracy are achieved through the stable thermal system, integrated automation and high performance.
Special geometry minimizes cutting pressure
Seagull tools are stable spherical and toroidal cutters with an extremely short cutting edge and special geometry to minimize cutting pressure in the production of graphite electrodes. The patented very short cutting edge (EP 2 540 427 B1/DE 10 2019 122 039 B3 ) of the Seagull cutters allows easy milling of graphite and other hard and brittle non-ferrous materials in dry and wet machining in the interaction carbide, diamond coating and geometry.
Seagull’s premium 567 and 577 series cutters offer very tight tolerances. Each tool is measured and the packaging label is provided with the actual values. Seagull’s quality 568 and 578 series shears are for price-conscious users. The 576.T3 toroidal cutter is new to the Seagull family. With its combined geometric characteristics and cutting edge dimensions, the cutter creates plenty of chip space for cutting volume and a high material removal rate for roughing as well as the finest engagement ratios for the finish.
The production time for the procedure with a copper and graphite electrode is extended by 180 minutes for a total of 3 hours and 57 minutes. Here too, machining centers from GF Machining Solutions equipped with 556 series solid carbide toroidal and spherical end mills enable Zecha tolerances of ± 0.005 millimeters and surface finishes of Ra 0.22 µm and VDI 7. Solid carbide o-rings for HSC non-ferrous metal machining are available in short versions with free length and precision ground, polished cutting edges and chip chambers. For an accuracy of the order of μ, Zecha manufactures this series of tools uncoated as standard or, on request, with a coating perfectly suited to machining.
High speed milling
High-speed milling is another injection mold manufacturing process. In the first two work steps, the roughing is carried out with a ball milling cutter with a diameter of 3 millimeters and feed rates of 4 meters per minute. Unlike machining with a larger tool, the reduced machining times mean that setup times and costs are reduced, as is the number of tool stations. Almost 90% of the total machining time is spent on finishing, which places the highest demands on the tool in terms of maximum surface quality, precision and tool life.
Tolerances of ±0.005 and surface finishes of Ra 0.1 micron and VDI 0 were achieved in all three machining steps within 60 minutes. The high-performance end mills and ball mills of the Peacock tool series used on the Mikron Mill S 600 U develop their potential in the machining of mild, hard and powder metallurgy steels up to 70 HRC.
The Peacock family is the innovation in Zecha’s line of hard end mills for high speed machining in tool and mold making. Peacock multiflute spherical and toric burs are available in different sizes: 581P series spherical burs in diameters from 0.2 to 12.0 mm and 583P and 597P series torus burs in diameters from 0.2 to 6.0 millimeters and 0.8 to 6 .0 millimeters respectively. The additional series 599 completes the Peacock line with immediate effect with new spherical and toric cutters in diameters from 0.1 to 12.0 millimeters. In addition, with the new 599.F4 and 599.F6 series – high-performance special cutters: 599.F4 with a finely ground protective radius of max. 0.05 millimeters and 599.F6 with a defined grind radius, providing additional edge protection. The new cutter design ensures high machining efficiency through high performance and wear resistance for a wide range of materials, alloy components and material hardnesses up to 70 HRC.
New coating technology in combination with the right solid carbide substrate, stabilized geometry, finest micro-geometry as well as rounded shank transitions cover additional applications in all component shapes and hardnesses. Even high alloy soft materials can be dry finished with cooling lubrication as well as high strength hard materials, not only roughing but also semi-finishing as well as fine finishing with highest precision and accuracy shape of the components. Minimized friction through optimized and homogeneous coating surfaces as well as coating adhesion additionally enables better repeatability and safety in application. The resulting potential for tool life and surface finishes offers significant added value for the customer.
The new CBN 950 range is offered as ball and toric end mills in the range of 0.2 to 2.0 millimeters. The high hardness of the substrate contributes to an increased life of form and dimensional accuracy. The specifically applied geometry achieves an optimal surface finish on the component. Also, this shape contributes to the stabilization of the cutting edges, which results in a long service life.
Combine milling and laser texturing
Complemented by digital laser technologies, aesthetic and functional texturing can be implemented and reproduced easily. Even complex 3D geometries, including precision parts, are precisely textured, etched, patterned, marked and labeled. With the Laser P 400 U from Schorndorf, the last step, i.e. finishing, can be replaced by the laser in the aforementioned process. Compared to the milling process with integrated finishing, the production time is reduced from 22 minutes to 37 minutes for the production of the injection mold. With the intelligent combination of milling and laser texturing, the two experts create an economical alternative for surface finishes of Ra 0.6 MIkrometer and VDI 16 as well as the lowest tolerances of ± 0.005 mm.
Together, GF Machining Solutions and Zecha cover all manufacturing processes with their product portfolios. For the customers of the two precision experts, this cooperation results in a wide range of possibilities, including the production of injection molds for medical technology. GF machines combined with Zecha molds make manufacturing with a wide range of technologies from a single source a reality. The resulting supplier savings enable customers of both experts to benefit from reduced costs. GF Machining Solutions and Zecha are continuously working on optimizing EDM technologies to increase machining speed and reduce electrode wear with highly polished surfaces of Ra 0.1 micron. This way, GF Machining Solutions and Zecha have the most economical and highest quality solution ready for each application with specified tolerances, surface qualities and production times. In the future, the partners will continue to optimize their machines and tools together to ensure the best possible added value and support for customers.