Laser welding is an effective method for joining small parts with tight tolerances. In the future, it will compete with traditional methods of welding or replace assembly/joining technologies benefiting industries that have never used laser welding before.
The Laser Welding Process
Using light in the form of laser radiation as the energy source is a process used to achieve a balance between the process of thermal fusion and metallurgical effects. Functionally, the laser generates infrared or visible light (usually with the use of Nd-YAG lasers or frequency-doubled “green” lasers for reflective metals) which is delivered through an optical fiber and focusing lens onto the workpiece. Welding is the process that occurs when laser radiation is absorbed by the workpiece and turned into heat raising the temperature in the localized area above the melting point. Movement of the worktable is controlled by CNC in order to produce 2 or 3 dimensional welds. The Focal Point is the “melt pool”. It follows the transition of stages on the surface of the workpiece. The newest techniques to synchronize laser pulsing with certain value of motion (fire on position of the encoder) creates an unprecedented quality of welds on complicated 3-dimensional objects. The quality of a weld is defined by the depth, width, mechanical strength, and hermetisity of the welds. It is ultimately controlled by speed and acceleration of the workpiece.
Applications Present Possibilities
Laser welding can be a powerful tool when used in conjunction with other machining methods for manufacturing scientific instrumentation, building medical devices, electronics applications, and consumer driven products.
There are various ways parts can be joined and/or machined to achieve desired functionality.
A micro gear made from 400 series stainless steel (in hardened condition) needed to be joined to a driver made of powder-metallurgical methods. A very high torque application was required for a mechanical strength test. The issue was resolved by running multiple passes of welding at relatively low energy penetrating deep into the material. Helium purge gas with special heat treatment was used to relieve the process stress without compromising the hardness of the parts. The method was successful. Currently these gears are flying in space.
Gateway Laser Services has developed a special process for welding a very thin-walled hypotube produced from 303 stainless steel. Although in the past it was considered unpopular to weld 303 stainless steel, now we apply this same method for that configuration to medical devices.