Reducing Unwanted Heating During Pulsed Nd:YAG Laser Welding
By Jay Eastman on Tuesday, September 21st, 2010
One of the goals of many pulsed Nd:YAG laser welding applications is to weld as fast as possible. The same applications, however, may also have component pieces that can be damaged by excessive heat. Pulsed laser welding of smaller assemblies at high travel speed and pulse frequency puts a lot of heat into the part in a short time. The heat quickly builds-up because there is little time for the heat to dissipate. I see damaged parts from customers. Glass-to-metals seals are cracked, non-metal parts near the weld are melted, and excessive distortion occurs. These problems can be reduced by simply slowing the pulse frequency and travel speed. This allows some of the heat from each pulse to dissipate before the next pulse hits. Therefore, the overall temperature rise of the part being welded is lowered. EWI has modelled this. These two videos are from computer simulations of pulsed Nd:YAG welding at 76 and 30-watts respectively. Both settings produced similar weld penetration. However, the 30-watt average power settings clearly do not build-up as much heat. If you can afford the increase in cycle time, simply slowing down the pulse frequency and travel speed along with modifying the energy per pulse can make the same weld with a lower overall temperature increase.
Thermal Model of Pulsed Nd:YAG at 76-watts
Thermal Model of Pulsed Nd:YAG at 30-watts