Laser Welding

16 02 2009

So the next move is to attempt to laser weld two pieces of steel. Having computer controlled laser welding at our disposal will be indispensable for constructing the core (beginning with welding the lids to the chassis) and the vacuum chamber (welding the chamber itself, welding various feedthroughs). I think we have enough wattage to laser weld stainless steel, although at a slow rate.  However, we still need to focus the beam, which is especially challenging for diode lasers that produce a bar beam like this:

beam_shapeIn my research, I found the back story to the lasers I picked up. Looking at the beam path illustration, these units correct for some of the diode array’s problems with divergence and astigmatism, so the output of the diode is a rectangular beam that focuses to a 1.5 cm long line about 15 cm beyond the output aperture.  So we are working with a well columnated beam, but it’s rectangle, not a circle. 

I think the easiest route to a top hat beam would be to focus this bar beam into a single thick core multimode fiber optic cable which results in a perfectly circular Gaussian spot, and an easy way to deliver the beam to it’s target where it would pass through a simple circular focusing lens. Challenges include sourcing the correct fiber optic cheaply, cleaving the fiber optic correctly, and aligning and focusing the bar beam into the fiber optic. This process would benefit from a Laser_beam_profiler, so you can find the sweet spot with focus and alignment for max transmission through the fiber. 

Here is a good overview of the basics of laser welding, including weldability of various materials.


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