Miniature Laser Welding
Laser welding is a discrete process and although filler material can be used to enhance joint strength and viability, the normal method for laser welding is to weld two surfaces together without “filler” or intermediary material.
In the medical device industry, the absence of a third material between two surfaces being welded together has advantages in that only the “parent” materials need to be approved for medical use.
Paarl Precision produces miniature metal assemblies by laser welding (laser spot and laser seam welding) and other micro-welding techniques. Metals which can be joined include stainless steels, nickel alloys such as Kovar, Monel or Hastelloy, titanium, platinum and other precious metals. The joint area is shielded with Argon to reduce oxidation in the weld area, rather than being placed under a vacuum, as is the case with electron beam welding.
Laser welding is therefore an economic solution when large quantities of similar assemblies require welding.
Rotary laser welding is particularly useful in joining the inside diameter of one precision tube such as an hypodermic tube to the outside diameter of a second tube, or for joining the ends of two different tubes or rods together. Seam welding along the join between circular stamped parts or fine blanked parts is also possible by rotary laser welding.
Special needles including biopsy needles can be made by laser welding a precision machined luer, for example, to a hypodermic tube. Other medical devices, such as drug delivery devices, catheters, venous filters and stents, can also be usefully assembled by laser welding. Components made from stainless steel or titanium foil can be laser welded together, for example in the manufacture of heart pacemakers.
Micro-sectioning of a laser weld shows that a seam of overlapping molten metal hemispheres, are formed from the individual “pulses” of laser light. These pulses are only milliseconds long, but are sufficient to melt the parent material on both sides of the weld. On re-solidifying, the hemispheres form a continuous precision seam weld.
In addition to laser welding similar materials, this technique can be used to weld together different materials. For example, copper wire can be laser welded to stainless steel components, creating a discrete, strong, electrically conductive joint.