Powder on, powder off: switching in milliseconds
Metal powder is one of the biggest cost drivers in laser material deposition (LMD). Until now, a significant share passes through the system unused, for example, when the laser briefly pauses while following a complex toolpath, but the powder continues to flow. The result is not only costly powder loss, contamination of components and handling systems, but also risks to equipment and occupational safety.
Existing solutions switch the powder flow mechanically, take more than a second and subject moving parts to wear. That is too slow and too costly for highly dynamic LMD and EHLA processes that require frequent, brief switching.
The Fluidic Powder Switch developed at Fraunhofer ILT instead switches the powder flow directly at the nozzle, where the powder enters the process. It works on the Venturi principle: A control-gas flow creates negative pressure at a cross-section constriction, drawing the powder into a collection container rather than directing it into the process zone. Since there are no mechanically moving parts in the powder path, the patented system operates with virtually no wear and requires almost no maintenance. In addition to simply switching the powder on and off, it can switch between several materials and adjust the powder mass flow in stages.
The economic benefit is substantial: Compared with mechanical systems, switching time is reduced by more than one order of magnitude. At the same time, the operating cost of the control gas is more than three orders of magnitude lower than the cost of the powder saved.
“Every gram of powder that does not pass through the system unused saves money, protects the component and conserves resources,” explains Viktor Glushych, group leader of LMD Coating and Heat Treatment at Fraunhofer ILT. Glushych played a key role in developing the innovative Fluidic Powder Switch. “We are particularly pleased that the switch not only works in the lab, but is already being used in series production by our first customers. That was exactly what we set out to achieve: a robust, cost-effective solution suitable for industrial use.”