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3D metal printer - linear axis positioning

3D metal printing is a popular manufacturing process in high-tech sectors such as medicine, aerospace, robotics and automotive. Parts with internal cavities or lattice structures can be produced, which is impossible with conventional methods. The amount of material used corresponds exactly to the amount required for the component, as there is no material removal like during milling or turning, but is produced in reverse order by material application (additive manufacturing). Structural components can be produced by hollow spaces with even lower weight and the digitized process chain between the design of the 3D CAD model and the finished part is a key factor for industry 4.0 implementation.

Materials such as stainless steel, tool steel, cobalt-chrome, copper alloys, titanium or aluminium alloys are melted onto the object layer by layer in powder form with one or more high-energy Yb-fiber lasers (multilasers), resulting in a homogeneous material with high strength and almost ideal material properties. 3D metal printers according to ATEX guidelines even allow safe production of components made of reactive material.

In addition to material properties, the focus is on surface quality and manufacturing accuracy with repeatable tolerances. Printed components are used for prototypes as well as for series production and can hardly be differed from conventionally manufactured parts. The exact positioning of the fiber lasers is of highest importance for the constantly increasing demands on the accuracy of the components. In the working process, the fiber laser is guided along the workpiece dynamically and with the highest accuracy at a constant distance via a linear system with several axes.

For position measurement and feedback to the machine control, Magnescale magnetic scales SL331 with PL60 reading heads and MJ100 interpolators are installed on each linear axis. The non-contact operating principle of the Magnescale magnetic scales is based on the magnetoresistive effect.

The high signal quality of the magnetically generated sinusoidal signal allows position measurement by interpolation with a very high resolution of 2µm and at the same time a high travel speed of 1800m/min, which was formerly only possible with extremely expensive optical systems. The magnescale magnetic scales are extremely resistant to shock and vibration, which can be difficult with glass scales. The output signal have to meet specific safety criteria and an alarm signal is activated if, for example, the maximum movement speed is exceeded, the signal of the reading head is below the nominal value or the cable is damaged. The Magnescale system provides a dynamic output signal with a phase difference of 100ns for a process-safe control of the position of the linear axis.

These features qualify the Magnescale magnetic scale SL331 with PL60 readeng head and MJ100 interpolator as an absolute guarantee for use in all industrial 3D metal printers and have been confirmed by the use of eddylab in the world's largest 3D metal printer.

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