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21 July 2015

Mapal turns to additive manufacturing for QTD series insert drills

QTD insert drill with AM-made shaft; note triangular spiral cooling hole, which is impossible to manufacture subtractively
Germany's Mapal has developed a competitive advantage in the tool market by manufacturing drills using metal 3D printing.

The new Mapal QTD series of insert drills offer a spiral cooling path in a tool as small as 8 mm diameter, extending the original range from its previous minimum diameter of 13 mm. In addition, a new non-circular coolant hole profile, only possible with AM, increases coolant flow. (The drill is offered in diameters from 8 to 32.75 mm, in four types for steel, stainless steel, cast iron and aluminum. They mount in four lengths of drill shank: 1.5xD, 3xD, 8xD and 12xD).

The QTD series insert drills are manufactured using additive laser melting (on a Laser Concept M1 Cusing machine, available in the UK from ES Technology, 01865 821818). 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, head of Mapal research and development, says: "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 further economise production.

However, the greatest advantage of transitioning from a conventional manufacturing strategy to additive manufacturing has been to facilitate an entirely new geometry, increasing the performance of the tools. Sellmer explains: "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 in a slightly triangular shape. Coolant profiles like this cannot be produced conventionally." Compared to a round shape, this profile optimizes the geometrical moment of inertia and increases the flow rate by up to 30%. The coolant flows at a pressure of 1.6 to 3 bar.

Two Concept Laser M1 cusing systems with a central material supply container (with stainless steel 1.2709) make the parts. The systems have a build envelope of 250 by 250 by 250 mm in X, Y and Z axes. Starting from a conventional shaft, the core of an insert drill is built with the cooling system. In a second additive run, the outer layer is built up with higher densities of metal. This two-stage process allows the drill to have the desirable material properties of being hard on the outside, to resist wear, and soft on the inside. We combine ductility with high tensile strength and hardness. The finished component is then heat-treated and vacuum-hardened.

The QTD insert drills are made in batches of either 10 by 10 or 11 by 11. 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 protective nitrogen gas atmosphere. 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.

The company, which had turnover of €510 million in 2014 and employs 70% of its 4,500 employees in Germany, bought the machines in 2013 and offered its first series-production parts 12 months later, in spring 2014.

Other Mapal tools have also benefitted from the new AM process; for example, a range of new weight-optimized, laser-melted external reamers. The lighter an external reamer is, the better it works, particularly when machining small-diameter shafts. Conventionally manufactured 8.5 mm steel external reamers already weigh 400 g; 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. "The mass distribution of the honeycomb structure of the external reamers is like wheel balancing," states Sellmer. "We call the internal cavities balancing profiles. The balancing profiles enable us to achieve virtually perfect concentricity of the rotating tools." A specially-designed rib structure, which has been registered for a patent, reduces the new 8.5 mm diameter external reamer's weight to 172 g. That is a weight saving of 57%, which results in a better performance for the rotating component.

Additive manufacturing strategies are helping Mapal boost competitiveness, economy and value added, according to the head of R&D. "In a broadest sense, we can say that the parts of the future are more intelligent or complex, and also offer better performance. 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."

Looking forward, he says that additive manufacturing will continue to be of value to Mapal's tool manufacturing processes: "We can assume that the build rates of laser melting systems will increase significantly. I believe multi-laser technology would increase the performance. That would allow either faster or more selective processing, that is, varying the layer thickness. The quality level will also increase. Together, this increases the economy and the performance parameters of parts. I also expect the range of materials available to grow, which will allow us to adapt components even better to their tasks in terms of performance or service life. Fundamentally, I could envision designing powder materials to suit the process and application optimally. Our design options will also change. 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. The process is doubtlessly ideally suited to increasing the imagination and creativity."

Will Dalrymple

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ES Technology Ltd
Mapal Ltd

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