Powder on Demand: Rapid-Powder-Switch

The use of Rapid-Powder-Switch during laser metal deposition (LMD) allows a powder savings up to fifty percent. With a short switching cycle of less than 200 ms, the powder is immediately available between processing cycles. Surfaces can be coated precisely and only where it is necessary – efficient and resource-conserving.

Use of the Rapid-Powder-Switch with combi-head. A change between laser welding (right) and cladding is possible without changing the tool. (Source: HD Sonderoptiken / Laserfact)

After switching on the powder feeder, many seconds pass before the powder flow runs stable and with a constant powder mass flow from the nozzle. If the powder feeder is switched off, the powder still trickles for a few seconds. The switching on and off of the powder feeder means a significant extension of the process time, a lower powder efficiency and thus the waste of valuable resources. In order to save time, the powder is often no longer switched off between individual processing steps. Depending on the application, up to fifty percent of the filler material is lost in this way.

Fast switching cycle allows significant efficiency increase

Harald Dickler – Sonderoptiken für die Lasertechnik (special optics for laser technology), in cooperation with the Fraunhofer Institute for Laser Technology ILT, has now succeeded in developing a Rapid-Powder-Switch which allows a significant increase in powder efficiency and thus increases the efficiency of the process. Not only resources are saved, but also considerable time savings are achieved. This is achieved by a rapid switching on / off of the powder gas stream, rapid switching between two powder gas streams and / or switching between two powder feed nozzles.

The powder gas stream can therefore be switched on and off quickly during the process without the laser beam being switched off. The powder which is not used for the process can be collected in a separate container and recycled. This opens up new production processes during laser metal deposition (cladding). For example, in the case of the inlet or outlet valve with blind bore at the shaft end, a wear-resistant layer could be produced by heat input by means of laser radiation and subsequent switching-on of the powder at a defined time for a melt-metallurgical connection without a bonding defect. This type of coating is not possible without the Rapid-Powder-Switch.

Surface, coated by powder pulsed operation (Source: HD Sonderoptiken / Fh. ILT)

In the course of automation and with regard to industry 4.0, machining strategies without changing tools are in great demand. With the Rapid-Powder-Switch, laser cutting, welding and cladding can now be realized with one machining head. Such a combi-head was developed by Laserfact and has already been successfully demonstrated at the AKL’16 – International Laser Technology Congress in Aachen. The powder was added or removed by means of the Rapid-Powder-Switch between the processing methods laser welding and cladding. Without the switch, this process technology is not feasible.

In addition to laser application cladding, the Rapid-Powder-Switch can be used in other areas in which powders are used, such as thermal spraying. (Source: HD Sonderoptiken)

Reference: H. Dickler & S. Tharmakulasingam: Powder on Demand – Rapid-Powder-Switch enhances economic efficiency in laser metal deposition and paves the way for new processing strategies, Laser Tech J. 14(5), 15-17 (November 2017); DOI: 10.1002/latj.201700028

Link: Harald Dickler – Sonderoptiken für die Lasertechnik

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