fine burr formation on top edge.

[badnisse]

new here and new to laser cutting so i hope someone here could help me whit a trouble i have. when cutting 4 mm stainless steel i get a great soft bottom edge free of burr but a very sharp top edge, feels a little like very fine burr. have a 7,5" lens and a 1,8 nozzel but cant remember gas pressure for now. where should i start to check for errors?

 

[cuttingedgelaser]

I use A 2.0 with 18 bar of gas and is burr free top and bottom. I sent an attachment to show you a picture. your focus, beam diameter, speed, all play a role in optimum cutting. what type of laser are you using? and how much power?

 

[badnisse]

well got a finnpower lc6 with Rofin Sinar 2,500 Watt diffusion cooled CO2 SLAB laser. Dont have the exact number but think it was 17 bar pressure and 2,1 m/min in speed and have a max setting of 2500 watt and a min of 2200. I think the focus is ok becus if i move it i get burr formation at the bottom again. Nozzel distance is 0,7 mm.

 

[cuttingedgelaser]

Try .040 on the nozzle standoff

 

[HenryRollins]

It sounds as if your focus would need to go deeper. What is it set at now?
-HR

 

[cuttingedgelaser]

-5.5 on the focus. What is yours set to?

 

[HenryRollins]

Sorry, I may have gave you the wrong answer. You have a fine burr, the type of burr that would feel like you are dragging your finger tips across a file or fine sand paper or is it heavier? Generally, I cut 4mm stainless at 4.2 to 4.6 depending on the grade of stainless.

 

[maayhemm]

Keep in mind my machine has a 4000 watt resonator but i use a 5,0" lens to cut anything below 0.1875" your focus point seems about right but your gas pressure seems high to me 2.0mm nozzle at about 12 bar should be ok. is your top edge just sharp or is there really a burr? I personally have never had a burr on the top edge but i do get a sharp top edge because the cut is so square.also for stainless your nozzle standoff should be less about 0.4mm.

 

[badnisse]

thanks for all the suggestions. Well would maybe say that is more of a very sharp edge like a razor blad then sandpaper, maybe is like you say that the cut is so square. is there any way around it or is it better to have it that way and deburr the top side of every pice made. the focus is set to 4.4.

 

[HenryRollins]

Ok, Top side where the beam enters the material and not the exit side/bottom of the plate? Is the lens in correctly?

 

[badnisse]

yepp. is the top where the beam enter, and the lens is in correctly. the flat side down.