100% Powder Efficiency in Direct Laser Deposition for Rapid Prototyping
BACKGROUND Direct Laser Deposition (DLD), which is also known as Direct Metal Deposition (DMD) or Laser Metal Deposition (LMD), is an additive ‘rapid’ manufacturing process in which a part is generated by repeatedly adding and fusing layers of material to a surface. A laser beam creates a melt pool on the metallic workpiece surface or previously deposited surface and additional metal, or alloy, powder is delivered to the pool to increase its size. Most current commercial DLD systems deliver the metallic powder by using a gas to carry the powder to the point of delivery through a feed tube and through a nozzle into the path of the laser. The major drawback of this method is that wastage of the expensive powder is very high; the powder is delivered at such a speed that it bounces off the target surface and also the powder feed stream size is larger than the laser beam spot size on the target (powder around the edge is not fused and is wasted). Wastage, if the powder is not recycled, is around 70%. Such powder wastage means that the considerable economic benefits of the whole process can be negated and hence deposition efficiency has received considerable attention, leading to the development of increasingly efficient nozzle assemblies. However, in most cases the reported deposition efficiency remains below 30%. Techniques which have achieved higher rates were at the expense of feature resolution and surface finish. THE TECHNOLOGY Researchers in the University of Manchester’s Laser Processing Research Centre have developed an alternative, gas-free, powder delivery method which gives close to 100% powder delivery efficiency, greater process control and improved surface finish. The method consists of using ultrasonic, or sonic, vibration means to deliver a stream or streams of powder through a feed nozzle or nozzles to the laser generated melt pool with the powder stream size smaller than the laser beam size on the target surface. As the powder is not delivered by pneumatic means (i.e. gas) the powder traveling speed is low (< 0.1m/s). Therefore, there is no bouncing back of powders from the laser generated melt pool. In addition, as the powder delivery is through a feed nozzle with small orifices (from 5 microns to 3mm diameter) the powder stream and powder particle sizes can be selected in a wide range without causing jamming or pulsing if the frequency of the sonic/ultrasonic vibration is optimized. It also allows rapid starting/stopping of the powder feed. TURNING INNOVATIVE THINKING INTO COMMERCIAL REALITY FROM IDEAS TO BUSINESS SUCCESS KEY BENEFITS The advantages of the new powder delivery technique include:• Substantial cost savings:
Negligible powder loss; no recycling of powder; no delivery gas required.
• Better surface finish:
The surface roughness achieved to date (5 μm – 20 μm) is better than that with existing DLD systems (20 μm – 70 μm).
• Better process control:
Automatic and instant switching (on/off) of the powder feed; precise control of deposition volume.
• Enables micro-prototyping:
Sub-mm parts with micro-metre features.
• A clean work environment:
Powders are not blown everywhere. APPLICATIONS The technology is applicable to the improvement of both DLD and laser cladding systems:
• DLD: Additive laser manufacture, and repair, of 3-D metal parts for:
• Turbine components.
• Engine components.
• Dies and molds for injection molding.
• Medical implants.
• Complex shaped metallic parts including jewelry.
• Micro-components.
• Laser cladding for the modification of surface properties (corrosion resistance, wear resistance) of engineering materials. INTELLECTUAL PROPERTY A patent application has been submitted in order to protect this invention. THE OPPORTUNITY UMIP would be pleased to hear from DLD and Laser Cladding system and service providers, and users of such systems, who would like to incorporate the 100% powder efficiency technology into their systems.
Type of Offer: Licensing
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