We have been having the machine for a little over a year now and have been able to reach our machining capabilities for the most part. Most of our jobs consist of .375"-.380" thick stainless round tubing varying from 2.0" - 4.0" I.D. We have been having the same problem from day one and we have yet to improve on it because I just can't seem to find help anywhere. I see videos of other laser machines cutting the same thickness of stainless tubing and NOT using a sacrificial rod of any sort inside the part. Then they proceed to not have any burn marks on the bottom of the reverse side of the cut and their cuts are extremely clean.
--Our most common operation in these tubes are 3/16" slots going around the OD in varying lengths and spacing--
Now I don't know if it's an issue with our setup, or maybe we are just doing something completely wrong. I have just always been told to max the power and dip the focus to -.280 and go for it. We have only ever resulted in burning the opposite side of the material until we put a bar in the part to prevent that from happening. The problem is while the bar is in the part it takes up a lot of room and stops the metal slugs and spray from the slots we are cutting out from vacating the part. So they end up getting stuck underneath our cut sometimes which causes a blowout and makes it extremely hard to get the bar out of the part.
If we had a way to cut these pipes without needing a bar we would definitely up our productivity almost two-fold. Most of our time is spent cleaning the parts out and hammering the now "welded" sacrificial bar out from the inside of our part.
If anyone has any tips or if they actually run a machine similar to ours with a similar application your opinions would be greatly appreciated. I have been scratching my head over this for entirely too long and it would be much appreciated to get some help.
Try using a thinner wall tube on the inside as apposed to a solid rod, like .125 Mid steel, It will scatter the beam on the back side and also let the slugs fall through. Unfortunately using a 2nd smaller tube is the only way I, or anyone else I know, have successfully cut tubing on a laser. Also, where is your N2 pressure set at on the cutting conditions? On 3/8 SS you want to have at least 16 bar (or psi equivalent) and might need to go higher. Hope some of that is helpful.
We have actually tried using a tubing on the inside before and the beam just shot right through it AND burnt into the backside of the pipe. I was thinking maybe we are using too much power, but from what it looks like the lower power machines can't even get through this thickness of material. We are pushing a good 150+ psi of N2 to help blow through the cut. I think we get somewhere around 170psi on our thickest material. I guess I can try bumping that up a lot more, but I don't know if our machine is rated to go that high. I'll have to check.
I feel like these youtube videos are bolognia and they lie to my eyes. They say they are laser cutting, but I guess maybe they are using fiber or some sort of really extreme plasma cutter?
Updating to bump, but I have had a bit of luck with being able to actually cut through the 3/8" material without burning the bottom side of the tube. The cuts look really bad and the spray that sticks to the inside of the part is incredibly difficult to get off even with our high grade anti-spatter.
Tube cutting with Mazak U-44 SpaceGear 4kw
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