Problem cutting 5 mm stainless on Amada FO-3015

[ozdan]

Hi, I would really appreciate any suggestions which can help me solving the issue I have cutting 5mm(3/16")316 stainless. No matter what I do or adjust I can't get rid off the burr on the bottom of the plate. I have no issues cutting 3mm (1/8") or less 316 stainless (which is what we usually cut most of) and I always get excellent cuts on the thinner materials. For the 5mm(3/6")plate,I followed Amada's recommended settings and fitted head 1 (5") instead of head 2 (7.5") we usually use for the thinner stuff.
I selected clean cut with nitrogen (c-sus-5.0). Nozzle size fitted is 3mm, power set to 4000w, feed rate to 1700mm/min,Frequency set to 2000, duty cycle to 100%, nozzle gap set to 0.3mm, gas pressure to 0.8Mpa I have tried the following without sucess.

1. Feed rate: 1700mm/min is the max I can do at 4000w(without it starting not to cut) and burr is still there
2. Power: I can go down to 3200w but then the feed needs to drop to 1200mm/min and burr is still there
3. Gas pressure: can go down to 0.45Mpa before it does not cut. I have been up to 1.0Mpa and yep,the ******** burr is still there
4. Frequency: have tried from 500 to 2000,not a lot of difference.you guessed it....burr still there.

Dont know where to go from here.

 

[SGAFFNEY]

I am not an Amada expert but do know Co2 laser cutting. One thing you did not mention is what I consider to be one of the most import factors in cutting SS. Focal Point. When you switched to the 5" from the 7.5" you made that even more important. I would start with adjusting the focal point and then possibly try a smaller nozzle, maybe a 2.5mm. That will increase the velocity of the nitrogen but reduce the volume expended. If you can successfully cut the 11 ga. you might consider going back to what works and make adjustments from there like lower focal point, higher gas pressure, slower speed since you are going up in thickness. Watch out for going to low with the focal point if you reduce the nozzle dia so you don't hit the side of the nozzle with the beam. That would be more critical with the 5" as well. Good luck and please let me know if any of this helps.

Sam

 

[ozdan]

Thanks Sgaffney you input is much appreciated, unfortunately it didnt resolve issue. I neglected to mentioned In my first post, that i tried various focus length settings but none removed the burr. As per your suggestion, I tried the 2.5mm nozzle and tried many speed and feedrate settings, was able to cut, but that dam burr was still there. I tried changing focus settings, none removed the burr, some made it worse. Tried changing gas pressure in increments down from 1.0Mpa to 0.4Mpa(under 0.4MPa it just wouldn't cut) and to be blunt there wasnt a lot of difference in result. I am pretty much come up against a brick wall trying to eliminiate this issue by settings.
As I previously mentioned I cut 1/16" stainless every day perfectly, but that is using the 5" head& lens. When I fit the 7.5" head & lens for the 3/16" stainless i get this problem. I'm starting to think perhaps I should buy and fit a new lens on the 7.5"and try that or try using the 5" head and lens to cut it (even though the Amada recomended setting is for the 7.5" head). Anyway would appreciate any thoughts on that.

 

[Foostrap]

Definitely use the 7.5" lens to cut 3/16" stainless. It's a lot more forgiving on your focal point. As you mention, use full power (4000W) and DC (100). Frequency won't do anything; just max it out at 2000.
A nozzle of 3.0mm seems a bit big. I would use a 2.5mm (2.0 might work as well, but 2.5 would be more forgiving). Your speed seems about right. Your gas pressure is too low though; you should have at least 1.5MPa. If your machine has a pressure sensor at the head, that would be nice to confirm you do get that pressure at the head (maybe you have a gas leak and are not getting that pressure). More pressure for stainless doesn't hurt, but you usually want to minimize it to save on cost. So it's always easier to start too high; get a good cut; then go lower until cut is no longer acceptable.
That leaves the focal point to adjust. If the burr is long and sharp, lower your focal point. If the burr is small, move your focus up a little bit. Don't hesitate to go by big increments when adjusting focus; 0.5 to 1mm at first; then 0.3mm to fine tune (that's for the 7.5" lens). If you lose the cut, your focus is too low. If you have a part with a mix of long and short burr, then something is wrong with the beam (mode, optics, bad lens,...)

 

[LaserLogan]

Not sure if you have had any luck with the 3/16 stainless, but here is the cut condtions that I use for our Amada 3015nt laser. and the quality is excellent and almost burr free, just some burrs around where it pierces.

Feed rate: 65 ipm
Power: 4000
Freq.: 2000
Duty: 100
Gas Press.: 0.90
Gas Kind: 7 (N2)
nozzle gap: .02

Lens: 7.5"
nozzle: D4.0E
Focus: -0.110

 

[ozdan]

Thanks laserlogan, Really appreciate getting some settings that work for someone else on the same material on similar machine. I wont get a chance to try these out for about a week, but when i do, I will certainly post the result

 

[Chally72]

Some parameters off of a Prima Platino:

Feed rate: 77ipm
Power: 2700
Freq.: 1000
Duty: 100
Nozzle gap: 0.047
Lens: 5"

Running at 65ipm, even with a 7.5" lens, you shouldn't have to go anywhere near 4000W.....

 

[ozdan]

Thanks to everyone who replied to my question, much appreciated. Laserlogan , your machine is very similar to Amada FO-3015 that I run, so the settings you suggested worked pretty well except that i am still getting a very small burr. I was able to go to 3800 watts and fiddled with speeds, nozzle gaps and gas pressures, but ended up with 1650 mm/m (65ipm) as pretty much the ideal speed. Nozzle gap 0.2, freq 2000, Duty 100%, N2 gas pressure 0.8,
I think the burr might be a focus issue or perhaps nozzle, but due to workload was not able to pursue this any further for the time being. As I dont use the 7.5" lens very often can you tell me what you have for the base focus setting for the 7.5" head. Any further suggestion to eliminate burr would be appreciated.