German machine tool manufacturer, Hermle, is integrating additive manufacturing capability into a 5-axis machining centre marking a significant leap in complex metal component production.
In contrast to the metal powder based laser melting process, Hermle’s metal powder application (MPA) generative manufacturing technology is a thermal spray process based on lower energy kinetic compacting, or micro-forging.
The result marks seven years of development at the company’s R&D centre in Ottobrunn, near Munich and a significant level of investment.
The hybrid machine, known as an MPA 40, has a powder application nozzle mounted alongside the vertical milling spindle and a heater built into the 4th / 5th axis rotary table.
Once a CAD file has been prepared, a high-energy jet of super-heated steam propels metal powder suspended in nitrogen through a Laval nozzle onto a substrate at three times the speed of sound. The impact creates local pressures of 10 GPa and temperatures up to 1,000°C. The result is localised super-plastic deformation, forging the powder particles together and onto the component surface. The fully dense, bonded layer is machined by metal cutting using up to five CNC axes, followed by deposition of a further layer. The process is repeated any number of times to produce the required component.
Micro-forging allows up to six dissimilar metals to be layered, with either a sharp or a smooth transition between them. Each metal powder requires its own process parameters, which are stored in a knowledge database within the machine control. Materials currently available are 1.2344 and 1.2367 hot-working steels, 1.4404 stainless steel, copper, bronze, titanium and aluminium.
Components produced can be up to 550 mm in diameter, 460 mm deep and weigh up to 600 kg with the option to use a water-soluble filler material to create internal features, such as conformal cooling channels in plastic injection moulds.
Although traditional additive manufacturing can achieve a similar result, Hermle’s MPA method goes a step further with its ability to micro-forge dissimilar materials, enabling mixed metal solutions like a heat-conducting copper core inside a tool steel exterior.
To coincide Hermle has developed MPA-Studio CAM software to enable layer-by-layer analysis and machining to build the component geometry. Simulation of the sequence and quality assurance functions for checking the finished components are included.
The firm is currently consulting with German customers to identify suitable applications, discuss how the process can be implemented and produce special, dedicated parts.