Considerable design freedom for complex tools thanks to AM

Until recently, it was unheard of to combine precision and additive manufacturing. Now, the first precision tool manufacturers are venturing into AM technology and have achieved positive results in terms of the production process and the tools’ precision and performance.

High performance, a long lifespan and quick tool changes are the core requirements for modern tool designs. A new development from German tool manufacturer Mapal meets all three with its new drill bit, which has good chip deformation and reliable chip removal thanks to its innovative geometry – the bit is held in a stable, prism-shaped connection. The high precision offered by the drill makes high cutting specifications and drill quality possible. This unique combination of characteristics was achieved thanks to an additive manufacturing technique based on laser-melted metal powder. By applying this metal powder-based AM technique, the manufacturer achieved better tool design and more efficient tool production.

Cool, narrow drill bit

The drill bit was previously available in diameters of 13 mm and more. One of the reasons for this was the coolant supply in the tool body: the narrower the tool body, the greater the adverse effect on the tool’s performance. A central coolant supply weakens the drill’s core and destabilises it. Besides, the cooling channels need to be even narrower, which reduces the flow to the drill head. The new steel tool body design with spiral cooling channels is not usually used for small-diameter drills, but thanks to this new design, even solid drills can be produced with a diameter of 8 to 12 millimetres.

The production process is characterised by the possibility of unmanned manufacturing and the shorter tool change times. Nevertheless, the greatest benefit of this new concept lies in its innovative geometry, which enhances the tools’ performance.

Production process

The new-series drill bits are hybrids: the shank (the simpler part of the tool) is manufactured conventionally, while the more complex drill head is laser-melted using additive techniques. This approach makes the manufacturing process far more economical. Moreover, unmanned 24/7 manufacturing is also a possibility.

Two laser cusing systems and a central material supply container are used to produce the drills. 100 to 121 drill bits can be manufactured in one set-up. The build rate of the 400 W lasers is between 6 and 18 cm³/h. The laser heats the powder to 60-70 °C for fusing. The amount of powder required for production is calculated on the basis of the actual construction weight plus 10%, and the scrap material is easy to recycle.

Internal tension in components is critical for rotating tool solutions. Due to the enormous forces to which they are subjected, tension must be removed from conventionally manufactured parts after machining. However, with laser cusing (a portmanteau of ‘concept laser’ and ‘fusing’), the design enables continuous cooling of the drill bit, resulting in more stable production.

Cooling concept

The cooling concept of this additively manufactured drill bit is based on spiral cooling channels, which improve cooling performance. The new design has increased the coolant supply by 100% compared to the previous design, and core stability is greater too. The new cooling channel profiles also contributed to boosting cooling performance: instead of having a conventional circular shape, they are slightly triangular, which optimises the geometrical moment of inertia and the flow rate. Cooling systems like this cannot be produced using conventional methods.

The new cooling concept results in better cooled drills, which are able to undertake longer drilling tasks. It also enables the production of drill bits with smaller diameters.

Reamers

The manufacturer has applied this technology to adapt a number of other products, including external reamers: the lighter they are, the better they work, especially when it comes to machining small-diameter shafts. Conventional 8.5 mm steel reamers weigh some 400 g – the weight and the resulting mass inertia limit the maximum speed. With AM techniques, lightweight reamers can be built with integrated balancing potential. The rotating components can be made almost perfectly concentric, while the weight can be reduced to 172 g. The lower weight means better performance: since the tool is faster, precision is greater.

The future

AM strategies can boost the competitiveness, economy and added value of a manufacturing process. The components of the future look set to be smarter and more complex while offering better performance. There is more freedom in terms of design too, which is bound to result in new geometries and new features. AM facilitates new product solutions that would have been inconceivable with conventional methods.

(images ETMM)