Additive Manufacturing Enhances the Precision of ToolmakingAug 19, 2015
Selective Laser Melting and hybrid manufacturing expand the design and production potential for Mapal
Mapal is a widely recognized developer and manufacturer of precision tooling, and now its developing a profile as a successful practitioner of additive manufacturing. Its new Mapal QTD-series drill inserts and HTC hydraulic chucks are demonstrating how AM techniques can be effective for industrial production of precision products.
High-performance, long-service life, and rapid tool-change times are the central requirements for modern tool concepts. The QTD insert drill excels with good chip deformation and reliable chip removal thanks to its geometry. The insert is held in a stable prism connection. These precision features make high cutting specifications and drill quality possible. Mapal offers four types of the inserts, for steel, stainless steel, cast iron, and aluminum.
While QTD insert drill was previously available in diameters of 13 mm and greater, additive manufacturing — using Concept Laser’s SLM technology, called LaserCusing — makes possible entirely new design approaches. Among these is the design for coolant supply in the tool body.
The smaller the tool body, the greater the adverse effect the standard central coolant supply on the tool's performance. Central coolant supply weakens the core of the drill and makes it unstable. In addition to this, the cooling channels must be ever smaller. That reduces the flow of coolant to the insert. The new steel tool body design with spiral cooling channels is not usually used for small diameters. The new design now allows even solid drills to be produced in the 8 to 12 mm diameter range.
The new QTD-series insert drill are manufactured using additive laser melting. These are hybrid-manufactured parts: The tool shank is machined conventionally and the drill is laser-melted with additive methods.
"Hybrid strategies are the ideal method of choice,” according to Dr. Dirk Sellmer, head of Research and Development at Mapal: “Simple component parts are machined and more complex areas are then built-up additively."
Unmanned manufacturing and a reduction of tooling-up times and reworking in the digital laser melting approach are other aspects that add to the value of Mapal’s AM production. However, the greatest advantage of transitioning from a conventional manufacturing strategy to additive manufacturing was that it facilitated an entirely new geometry, increasing the performance of the tools.
"The additively manufactured insert drill has a cooling concept with spiral ducts, which improves the cooling performance,” Sellmer explained. "Compared with the previous central coolant supply with 'y' diversion, a spiral coolant routing increases the coolant flow by 100%." It also increases the core stability with coolant ducts that run parallel to the flute. Cooling is improved by the new coolant duct profiles too, which deviate from the usual circular form with a slightly triangular shape. That optimizes the geometrical moment of inertia and the flow rate. Tests found that choosing a cross section of this type increases the flow quantity by 30%. Coolant profiles like this cannot be produced conventionally. The coolant flows at a pressure of 1.6 to 3 bar.
Overall, the new cooling concept means that better cooled drills are available for longer drilling tasks. It makes it possible to expand the range with smaller drill diameters.
Stainless steel 1.2709 is used to manufacture the QTD insert drills. According to Dr. Sellmer, the powder requirement is calculated from the effective construction weights plus 10%, and the scrap material is easy to recycle. Internal tension in parts is critical for rotating tool solutions by Mapal. Tension must be removed from conventionally manufactured parts after machining due to the immense forces to which they are subjected. Not so with Concept Lasers’ LaserCusing. The constantly changing exposure locations in the geometry mean that the tension is removed from the part internally during the build process.
Two Concept Laser M1 LaserCusing systems are used, with a central material supply container. The systems have a build envelope of 250 x 250 x 250 mm. The QTD insert drills are created as 10x10 or 11x11 units: 100 to 121 drills are produced in one set-up. The build rates of the 400 W lasers are between 6 and 18 cm³/h. In order to avoid contamination, and the M1 operates under a protected atmosphere of nitrogen gas.
During processing, the laser heats the powder material to 60-70°C for fusing. Thermal expansion in the build process has to be taken into consideration in the design. However, after initial successes with series products, the demand for internal capacities is also growing, even though clever organization results in production availability of 24 hours, seven days a week with unmanned production.