In times when components are becoming increasingly more complex and more individual additive manufacturing processes, with their high degree of geometric freedom with regard to component design, rank as a proven way out of the complexity trap.
However, the technology is seen as slow, inaccurate and expensive; an attitude that has hitherto made its entry into the market difficult, especially in the metal machining sector. In the light of the above, the combination of laser deposi-tion welding using a powder nozzle combined with machining opens up completely new perspectives.
In the field of additive manufacturing the powder is melted onto the base material by the laser beam. Unlike other laser-based processes in additive manufacture that work according to the layer principle, whereby a component is built-up layer by layer from powder material.
“We also build up layer by layer, but we only use the powder where it is actually needed”, says Friedemann Lell, sales manager at Sauer GmbH, pointing out the significantly lower quantity of powder used. Other advantages include the around ten times faster build-up of the material and simple integration into existing machine tools. “This allows the integral combination of additive and machining manufacturing in a single setup, so we can offer our customers the best of both worlds.”
By the best of both worlds it means that additive manufacturing on its own still has its limits with regard to speed, accuracy and surface quality. But proven 5-axis machining can compensate these limits. The combination of additive manufacturing and machining brings us the geometric freedom, while machining guarantees the precision and quality of the component. The time-saving benefit derives from the fact that no sequential production necessitating a machine changeover is necessary.
In practice this combination of the two technologies allows completely new complexities. Friedemann sees examples of this in the free formed geometric elements in turbine and engine construction and in the internal cooling channels of injection moulds: “In the case of sequential manufacturing it would not be possible to reach many of the contour areas with turning, milling or grinding tools after additive manufacture.” In the final analysis, every component can first be built up to a specific height and then certain areas machined. “Large components in particular can be manufactured cost-effectively in this way.” So the unique interplay of the technologies results quite literally in free formed workpieces that feature high precision and excellent surfaces.
Getting Ahead In Additive Manufacturing
DMG Mori offers hybrid machining in the form of the Lasertec 65 3D whose basic design is similar to that of a classic 5-axis machine for high-precision milling operations with up to 5-axis simultaneous machining. For additive manufacturing the machine has been equipped with a 2.5 kW diode laser. So the machine is suited for the complete hybrid production of components as well as for repair work and applying partial or full coatings, for tool and mould making, for example.
As of 2016 the company is expanding its additive manufacturing programme to include the
Lasertec 4300 3D. This second hybrid machine will add the possibility of turning operations to laser deposition welding and 5-axis milling, so that rotation-symmetric components can now also be produced with the hybrid process. Equipped with a mirrored C-axis workpieces can also be machined on the rear side with the counter-spindle thus enabling in total 6-sided complete machining of the finished part. Not even longer workpieces present a problem, because in this case the lower tool turret supports the component during machining.
In both machines the laser, including the powder application head, is installed in the HSK tool holder of the milling spindle and if required can be changed over automatically. An additional special feature of the machine is that there are up to five powder deposition heads available for different operations – for inner or outer coating of cylindrical components, for example. This creates extra degrees of freedom with regard to the manufacturing strategy.
The expectations of the both the machine tool manufacturer and the customers have been confirmed now that DMG Mori has already installed a number of Lasertec 65 3D machines on the market. However, Friedemann does not as yet see additive manufacturing as a standard process. He says, “That would awaken false expectations. Additive manufacturing, especially in metal machining, is a complex process, which depends like nowhere else on the perfect interplay between machine, material and process.”
This means, for example, that the process must be newly developed in all its parameters for every material. “We support our customers intensively in this respect and cooperate very closely with research institutes in the field of material and process development.”
Driven by the fascinating possibilities of this process and based on ever more impressive examples of success, especially in the field of aircraft construction and medical technology at the moment, additive manufacturing ranks as one of the future technologies in metal machining.
This applies in particular in view of digitalised processes in the era of Industry 4.0 and the trend towards individualised products. Friedemann says, “Anyone wishing to produce finished products directly from CAD data needs additive manufacturing. And if high-precision and excellent surface qualities are also required, then our hybrid machines are what is needed.”
Lasertec 65 3D whose basic design is similar to that of a classic 5-axis machine for high-precision milling operations with up to 5-axis simultaneous machining.
Technology integration made by DMG Mori: Laser deposition welding and 5-axis milling combined intelligently for best surfaces and prefect component precision.
Hybrid CAD / CAM - module for the laser and milling process: integral solution for additive build-up and subtractive machining for construction, programming and machining.
