The days when precision tools and additive manufacturing strategies could not co-exist are history. The new Mapal QTD-series insert drill proves this. For the first time, the precision tool specialists from Aalen are manufacturing drills additively, with amazing results. Dr. Dirk Sellmer, Head of Research and Development at Mapal, explained the reasons behind this new development and the new geometric freedom for designing complex parts.
Mapal is a think tank for high-tech drilling solutions. While searching for new, innovative metalworking solutions, the company has re-invented itself again and again in the 65 years since it was founded in 1950. In this pioneering role, Mapal now relies on additive LaserCUSING systems by Concept Laser.
Requirements in practice
High performance, long service lives and rapid tool changes 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.
New QTD insert drill with diameters from 8 to 32.75 mm
The Mapal QTD insert drill has a lot to offer in detail. Additive manufacturing from metal powder using laser-melting systems makes entirely new design approaches possible.
The QTD insert drill was previously available in diameters of 13 mm and greater. One reason for this is the coolant supply usually housed in the tool body. A central coolant supply weakens the core of the drill, which makes it unstable. In addition, the cooling channels must be 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. But it allows even solid drills to be produced in the 8 to 12 mm diameter range.
New, spiral cooling concept
The new QTD-series insert drills 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. This approach makes the manufacturing process significantly more economical.
Dr. Dirk Sellmer: “Hybrid strategies are the ideal method of choice: 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 which improve the economy. However, the greatest advantage of moving from a conventional manufacturing strategy to additive manufacturing was that it facilitated an entirely new geometry, increasing the performance of the tools.
Dr. Dirk Sellmer: “The additively manufactured insert drill has a cooling concept with spiral ducts, which improves the cooling performance. 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, which run parallel to the flute. The cooling is also improved by the new coolant duct profiles, 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 also allows expansion of the product range with smaller drill diameters. Stainless steel 1.2709 is used. 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. That is not the case for 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 cusing systems with a central material supply container are used. The systems, from the medium performance range, have a build envelope of 250 x 250 x 250 mm. The QTD insert drills are created as 10 x 10 or 11 x 11 unit solution in this build envelope. 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, the M1 cusing operates under a nitrogen protection gas atmosphere as usual. During processing, the laser heats the powder material to 60-70°C for fusing. The 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. According to Dr. Dirk Sellmer, options include using multiple lasers in a system and a general expansion of capacity. In 2014, Dr. Kress, owner of Mapal, mentioned a need for at least 5 systems in the medium term.
Why Concept Laser?
If you ask Matthias Schneider, an employee from the Dr. Sellmer’s R&D department, the reasons for choosing Concept Laser are handling, accessibility and user-friendliness. Matthias Schneider also mentions open variation of parameters for process design as strengths of Concept Laser. Variable parameters are particularly interesting for tests and new products to define an optional process. If we take a closer look, some things Schneider mentions make it clear that he knows what he is talking about: The topology options for LaserCUSING are among them. Concept Laser systems stand out due to their stochastic control of the slice segments (also referred to as “islands”), which are processed successively. This exposure strategy induces the lowest tension in the component.
Geometry and lightweight construction for balancing
The changes in the design are also apparent in other areas at Mapal. The Aalen-based company’s weight-optimized, laser-melted external reamers are new. The lighter the external reamers are, the better they work. That is particularly true for machining small-diameter shafts. Conventionally manufactured 8.5 mm steel external reamers already weigh 400 grams. This weight and the resulting mass inertia severely restrict the maximum step speeds. Additive manufacturing allows lightweight external reamers to be built with integrated balancing potential. Dr. Dirk Sellmer: “The mass distribution of the honeycomb structure of the external reamers is like balancing wheels. We call the internal cavities balancing profiles. The balancing profiles enable us to achieve virtually perfect concentricity of the rotating tools.” A rib structure, specially designed for the application, which has been registered for a patent, reduces the “new” 8.5 mm external reamer’s weight to 172 grams. That is a weight saving of 57%, which results in a better performance for this rotating component: Machining is faster and precision is greater.
New products on the horizon
Additive manufacturing strategies have been shown to boost competitiveness, economy and value added. “In a broad sense, we can say that the parts of the future are more intelligent or complex, and also offer better performance,” continues Dr. Dirk Sellmer, and adds: “They also give us new design options. And that will result in new geometries with new performance features. In general, additive manufacturing facilitates new product solutions, which would be inconceivable with conventional methods. Every project implemented is a learning experience. This knowledge is then used in new, future projects. “Besides optimizing the quality, Mapal prioritizes process management, to manufacture additively with better surfaces closer to the precision component. Both cryogenic chip removal and the requests for closed cooling circuits and chambers make new requirements of the technology.