The best of both worlds

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Alternate deposition and removal on five axes

MPA technology is a thermal spray process for metal powder. When depositing the material, powder particles with grain sizes of 25 to 75 µm are accelerated to very high speeds by means of a carrier gas and applied to the substrate via a nozzle. The material is deposited in layers until the contours of the component are accessible for milling. After machining the contours, the deposition process is repeated. “Alternate deposition and removal is carried out on five axes using an in-house CAM development, Hermle‘s MPA Studio," says Derntl. “Up to six powder conveyors can be controlled simultaneously. This enables functionally graded materials to be produced and material mixtures to be generated. There are therefore no limits to the process in the metals sector.”

According to Derntl, the strength of MPA technology lies in the deposition of large volumes on semi-finished products with free-form surfaces in combination with cavities such as cooling channels or integral heating wires. “These are applications which cannot be covered by any other generative manufacturing process. Workpiece dimensions of more than 0.5 m x 0.5 m with total weights of several hundred kilograms are nothing unusual for us.” He also emphasises the possibility of combining materials, a feature which laser deposition welding does not provide. “In contrast with deposition welding, in the MPA process, the deposited powder is not fusion bonded, which means that the resulting stresses in the component are very small,” says Derntl.

Efficiency at maximum precision

DMG Mori‘s hybrid machine is equipped with a 2 kW diode laser. It is based on a DMU 65 Monoblock and was developed by Sauer Lasertec in collaboration with DMG Mori USA. “The absolutely unique feature of the Lasertec 65 3D is that it enables laser deposition welding and five-axis milling to be combined in a single setup, thus making it possible to produce highly complex components,” says Friedemann Lell, sales manager for laser machines at DMG Mori Seiki AG. “For example, many 3D geometries with undercuts can be realised in this way. This opens up design options which would have been unthinkable before.” A component can therefore be designed for optimum functionality without taking into account specific manufacturing restrictions.

Laser head with integral cooling and process monitoring

Lell expands further on the concept: “Our experience with the integration of laser heads into machine tools has stood us in good stead with the hybrid machine, as demonstrated by the automatic shuttle handling for changing the laser head and the HSK-63 interface. However, for laser deposition welding, we use a new laser head with integral cooling, process monitoring and an integral camera that controls the process optically and adjusts the laser power online.”

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