Mar 9, 2018 | By Benedict

The Fraunhofer Institute for Laser Technology ILT has developed an inline system for testing, qualifying, and adjusting the focused powder jet of laser metal deposition nozzles. Laser Metal Deposition is an additive manufacturing process that uses the technology of laser cladding.

Laser Metal Deposition, an advanced 3D printing process perfected by engineers at Germany’s Fraunhofer ILT, can be used for applications like repairing tools or applying anti-corrosion coatings. But certain aspects must be just right for the process to work properly: the laser beam must apply the powder evenly, for example, else the outcome will be less than satisfactory.

To ensure even distribution, the nozzles and caustics of an LMD 3D printing system must be regularly checked, certified, and calibrated—a complex and tricky process, usually achieved by applying a powder trace on a metal sheet which can then be checked by an expert.

Because this difficult task can only be carried out by a highly qualified member of staff, Fraunhofer ILT decided to create a new means of testing nozzles. Its new machine-supported inline process makes the process much easier, and consists of three main components.

The first of these is a camera module, complete with movable optics and illumination, which is mounted on the machining head. The nozzle is measured with a laser module, which is placed in the system, while electronics integrated either in a separate section or the machine control cabinet control the other two modules.

(Images: Fraunhofer ILT)

The jet is illuminated with a laser line perpendicular to the powder gas flow, and observed by a coaxially arranged camera through the powder nozzle, a process that serves to detect and measure the particle density distribution and caustics of the powder jet.

The new ILT system changes the relative position of the laser and the machining head several times in order to record more measurements, before evaluating 2,000 to 3,000 images to show the statistical distribution of the particles in one plane.

“If I use this method to gradually capture the so-called caustics—i.e. the focusing area in which the powder particle beam is bundled—it can be calculated and characterized very precisely in terms of the most important parameters, such as the minimum diameter and the density distribution,” says graduate engineer Oliver Nottrodt, project manager for Process Control and System Technology at Fraunhofer ILT Nottrodt.

This measuring system for Laser Material Deposition enables a user to measure and certify the powder feed nozzles and also completely characterize the powder used in the additive manufacturing process. It will be demonstrated at CONTROL 2018 in Stuttgart at the end of April.



Posted in 3D Printing Technology



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