N2 cutting Mild steel

[RoyMultishape]

I am running an Amada Lc1212 and am looking for increased productivity on low gauge mild steels.

The latest lasers cut at 20M + per min (1MM mild steel) and they use high power and loads of gas to achieve this.I also know there is a limit to the speed that Oxygen can cut due to exothermic process, and this is why they switch to N2.

Does anyone have data for high speed cutting Mild steel with N2?
If so has anyone tried using lower grade N2 (96%) when cutting?

 

[chadxyz]

Hi, RoyMultishape

Yes there is a limit to achievable speed when cutting with oxygen due to the balancing of the exothermic reaction. For cutting thin mild steel at high speeds, high pressure Nitrogen is your best bet. And using lower grade nitrogen will usually cause your cut edge to exhibit a rusty oranges brown color and decrease your maximum cut speed. A question back to you though, have you noticed when cutting at higher accelerations that your cut tends to jitter especially at corners or block changes?

 

[RoyMultishape]

chadxyz

Yes i do get jittering,
I get this when I cut stainless at high speeds, when the laser turns corners dross appears on the rear side, as you said also on block changes. This i think is due to the laser hesitating momentarily as it turns the corner or reads its next command. There are cures such as edge data, which slows the laser down just before a corner then speeds up after, but from experience all corners are different and not every job is rectangular, we normally end up second opping the part with a graining or deburring operation.

 

[JayMaechtlen]

The last I heard, Amada still has guys doing applications work. When I worked there (for a long time in Laser group) we never charged to help the customer with apps info.

Call them!
Jay



Jay Maechtlen

 

[chadxyz]

I am guessing you use a gantry style machine equipped with AC servo drives? It seems most servo drives have this flaw. At high velocity the PWM signal seems to bounce. Kind of like backlash, this is not good for high speed cutting. I've heard of using edge conditions in newer machines, also looping corners can work in some conditions. The old stand by is to switch cut conditions to pulse cutting before and through the corner then return to high speed conditions. That usually works the best, but it can add significantly to your cycle time. Just curious has anyone used a linear drive machine, does it have the same characteristics?

 

[JayMaechtlen]

The Pulsar (LC1212) is not a gantry machine. It does, however, use AC servos.
I an not sure what kind of problem you are trying to describe? Normally, the special treatment at corners is to control heat in areas where the machine necessarily cannot maintain programmed feedrate.
The corner problem tends to be worse with high programmed feedrate on machines with limited accel/decel.
Jay


Jay Maechtlen

 

[chadxyz]

The problem I'm describing comes from coupled motion (simultaneous X and Y motion) usually at high speeds and during block changes. After a corner or block change there is a tendency for the cut edge to have a small wiggle in it. It is usually only noticeable at higher speeds. In gantry machines this is even more pronounced due to the incorporation of an overlay drive. I have seen the jittering problem in both gantry and hybrid machines. Sometimes you can actually tune this "jitter" out of the drive, by adjusting the gain. But for the most part "jittering" seems to be a common side effect with most AC servo drive systems.

 

[JayMaechtlen]

Depending on the year/model of the machine(control), what you want to do might or might not be do-able. AFIK, those weren't really super-high speed machines.
Again, have you asked the vendor?
Good luck


Jay Maechtlen

 

[Co2Laser]

Have you tried using shop air as an assist gas. I use a 120psi compressor, run through a booster and a dryer, to achieve 500psi. One mm CRS cuts @ 600 IPM With minmal browning or orange color. The thinner the material is you cant even see it. You can still do this with as little as 80 psi, but just about everything in the shop will go down due to the probable lack of volume. Note air cut materials CAN be powdercoated.

As far as the jittering, can you get into the acceleration rates of the machine? Usually they are set around 80in/sec2. Try going up to 140in/sec2. If you can't do this, a simple "dwell time" command around the corners will help. I generally have used a dwell time of 0.1s per move. Sometimes you can also couple this with a M61 and M60, which forces the machine to execute the programmed block before reading ahead.

Good luck