Stainless steel cutting on Bystronic 4020 3kw

[imren]

I have a problem with cutting stainless steel.
I started to cut with N2 5.0 and managed to get a fine cut. My focus point was +4.0, the gas pressure was around 11bar.
After that I changed the cutting gas to O2 and continued cutting steel, the cut was horrible. But before cutting with N2 it was ok. I tried everything and when I finaly changed the lens the cut was fine again.
I spoke with a bystronic service and he said that it is because of the reflection from the staliness steel.
On the lens I cant see any scratch or cracks but somthing happend to it.

Could anyone explain this?

Best regards,

Imre.

 

[Barneylaser]

You probably stressed the lense

http://www.iiviinfrared.com/pdfs/II-VI_LSA002W_datasheet-01.pdf

maybe your machine came with polarization cards to test this?

I would suggest you cut .187 and up Stainless with a 7.5" not a 5"

 

[JeanFreli]

You have to be more specific about the thickness and what you were cutting.If you were cutting steel with n2, it was sure very thin steel and a focal +4 is very big. To cut steel you need o2 and not a lot of pressure gaz. With ss you should use a focal negative with a lot more pressure of n2. Cutting steel with a laser is very cool but you need to set it very good when you start especially the nozzle.

 

[Barneylaser]

They said "continued cutting steel"... I assume they were cutting Steel went to a Stainless Job and came back to the steel...Then the problems started....Also sometimes A lense just goes bad and needs to be changed. This might have happened just at the wrong time. Coincidence...maybe

 

[imren]

The staliness steel was 3mm thick, and we were cutting with the 7.5" cutting head.
When the focus was -1.2 (like i would use for mild steel) the cut left sharp jagged edge.
With the +4.0 focal point the cut was smooth, perfect. But after we went back cutting mild steel
the cut was bad.
As the I said the technical service also said the lens was probably stressed (reflection).

 

[HenryRollins]

If you lens were stressed then cutting N2 would be a rough cut. Burrs and the like. A quick test would be to cut a few strip cuts on some stainless, 7 gage should do fine, and let the lens cool down and cut them again. If you have a difference in the strip cuts (first series of cuts were smooth and burr free and the second set had fine or jagged burrs), then the lens is stressed. What was the focus for the O2 cut? What size/type of nozzle? Have you checked what the O2 pressure was at the service unit for the outgoing O2? Are you getting any gas alarms? Missing any of the O rings in the back of the head and carriage? Have you tried a new nozzle? Just a few things to check out before you buy a new lens.
-HR

 

[krugtech]

do you know how to check the lens w a polarizer? from one of my other posts- If anyone uses polarizing filters to check their lens, here's an easier way to do it. Normally you would lay a polarizer on a diffuse light source, lay a lens on top of it and place another polarizer on top of the lens. Rotate one of the polarizers until all the stress in the lens appears.

easier way- open notepad on a computer with an LCD screen. The white LCD screen is an excellent polarized diffuse light source and you probably have an LCD screen on the laser anyway. Then get one ploarizing filter or even a pair of polarized sunglasses and hold the lens between the light source and polarizer filter. Rotate the polarizer and if there's any stress in the lens you'll see it clear as day.

My customers will try this and not see anything, maybe they'll see some clovers where the lens clamp ring was pressing on the lens. Then they'll find a lens that looks fine but the polarizer shows all hell breaking loose inside. As you rotate the polarizer the amount of light coming through should change, if it doesn't then you don't have an LCD screen or the polarizer isn't a polarizer.


Chris Krug

http://krugtech.com/

Maximum Up-time, Minimum BS