I initially thought this would be impossible due to the low power of the laser, but from [what I can find][1] on [laser welding][2] you only need 1KW for every millimeter of penetration at 2M/m. This suggests stainless steel SLS printing with a 0.1mm or smaller layer height might be possible with our laser at around 18mm/s.
This seems far too promising. Anybody else have some insight?
[1]: http://ewi.org/how-much-laser-power-do-you-need-for-welding/
[2]: http://www.jklasers.com/laser-welding
Scaling a rule of thumb designed for 5-10mm plate down to 0.1mm will yield some major variations, so expect to work at a dramatically lower speed than you estimate.
Second, unless your going to use a flux or inert gas, you will have oxidization problems with lazer welding. The reason they can avoid its use in some commercial applications is they use a very high output (often >2kw) pulsed lazer, so they heat a spot to molten then let it set before moving forwards one step, resulting in minimal surface area seconds of molten metal to air contact in which undesirable oxidation can occur. We don’t have this luxury, our low output 60w lazer will require more time to heat, and using a lower layer height will make the oxide coating a more significant percentage of the total working area, so 0.1mm thick probably won’t have much in the way of un-oxidized material. Also remember that before a second layer can be applied you must remove what oxide was left from the last pass, this isn’t a problem for lazer fusion (due to fusing the two parent metals, as opposed to applying filler) welding since normally only one pass is ever applied, but in a 3d printing application necessitates a second system to preform a cleaning pass every layer.
All in all I’m not saying it can’t be done… but its not like our current system is anything like ready for this kind of work, nor would I like to see you try and convert it given you’d be changing a perfectly good lazer cutter into a experimental 3d printer that’ll always be slightly handicapped by its low wattage tube and the fact it was originally designed for a different purpose. On the other hand if you where to acquire your own machine to convert I’d be glad to lend a hand since its one hell of a cool project, and I get the feeling some welding knowledge may be handy for a project that involves joining metal.
Obviously modifying the laser cutter would be insane. I was thinking more along the lines of a drop-in powder tray to see if it’s possible to even fuse metal at that power. What if the powder is a mix of stainless steel and powdered rosin?
Just testing it could be as simple as sprinkling a single thin layer of SS powder onto a sheet of non - laser able backing like a solid block of SS … and lasering it. … seems like an interesting rest to me.
Also… you could change the air - assist line to feed argon if you are worried about oxidation. … i have a bottle of argon and guages u could try it if u want. … just need to ensure the volume of gas is very low so as not to blow the SS powder around.
If you have a pressure regulator on that cylinder then it’d be as simple as hooking up to the line that’s normally the air assist. Also I’d think you’d want to use something less thermally conductive than a solid SS sheet for the back-plate, like for instance a thermal tile, although a very low thickness sheet may still work since SS is still less thermally conductive than mild steel.
Placing dry ice over the air assist inlet could work. It would be cheaper than argon too. It might cool the weld too much though.