Serrated Edge?

[Charlene]

Okay, I have been trying different things to get rid of a fairly severe serrated edge when cutting letters (curves). I have changed back to 20:1, changed the THC rate to -15, changed how we index the torch plate so that it doesn't vibrate, and played with profile settings. I have been able to eliminate most of it but it is still there. The one thing that I haven't messed with is motor tuning. It has been suggested that I may need to adjust acceleration/velocity but I don't know what to change the numbers to. I figured that this would be the best place to ask since we all basically have the same equipment. I have also read that there might actually be something in the GCode that can make it happen... Is that accurate? Any suggestions?

[Charlene]

Oh yeah, I also changed the span gap to 10/4.

[jeepsr4ever]

Use 18 not -15. Also email us your Gcode.

[jeepsr4ever]

From your cuts that you emailed I show these possibilities

1. Your consumable is worn
2. Your air pressure is too high
3. Your moving too fast for your amperage
4. Your tip volts are too high

Your cuts are so rough I would blame your consumables but serrations are usually caused by too fast of travel for your amperage.

[Charlene]

I just emailed the gcode to you. I have already replaced the consumables; I have tried a psi range of 66-72; an amperage range of 40-45 amps; speeds of 120-150; and, tip volts from 83-100.

Here is the original cut:

223

And, here is how it looks currently:

224
225

[jeepsr4ever]

So did you try slowing it way down? Did you try new consumables?

[Charlene]

I will try the speed tomorrow. I replaced the electrode but the nozzle looked pretty good. Tomorrow I will replace the nozzle and the ohmic retaining cap to see if there is any difference.

[jeepsr4ever]

Yet another possibility is the PC isnt sending signals fast enough. If everything is right that cut should be buttery smooth. Something is wrong and thsoe cuts look horrendous. I know some PCs can get overwhelmed when you have too many programs running.

[Charlene]

Okay, I will check our computer cable to be sure that it hasn't been damaged.

[jeepsr4ever]

A quick way to tell is to hold the trigger on your controller and jog the machine. If you see any jitters then there is a motion issue. If not it doesnt rule out the PC but it may rule out the table and electronic controls.

[Charlene]

Alright, I changed all of the consumables except the ohmic cap (don't have another one right now). By the way, what would I look for as indication that I need to change the cap? My computer is the same as wickedinhere's computer so it shouldn't be the problem. I don't have another port plug cable so I will go get one. I ran the file again with the new consumables and the lines are pretty much unchanged. One thing I noticed during the cut was the sound of the torch air flow. When it was cutting the sections where it leaves the jagged edges, it makes a sound similar to what it would sound like if I were cutting expanded metal really fast. I videoed the cut and will email it to you. Please ignore the sparks, I forgot to turn the speed back down. (It makes the same sound when I had it set at 120ipm too).

Thanks!

[jeepsr4ever]

Please update Charlene :)

[tlspeed1]

Any more info on this Charlene? I recently cut some 12 guage and noticed the same problem. I have yet to look in to and test all the variables, but would like to know if you found anything.

here is a pic of what I was cutting....though it doesnt show the serration problem.

226

[jeepsr4ever]

If you go to settings and if your THC rate is at 30 you will have serrations from the Z axis oscillation. Change the value to 18 and try the cut again. THC rate the the frequency in time the Z axis will make adjustments.