Problems Cutting 3/4" Mild Steel (HELP!)

[evoandyvii]

Hello I have a TD Cutmaster 152 set up on a water table. I'm using SheetCAM and Mach3 to run the drawings on the table. I recently got it cutting thin metals such as 1/32" to i believe the thickest is 1/8". I recently received a job to cut exhaust flanges that are 1/2" and 3/4" mild steel. I was making really good progress on the thin stuff but this thick materiel is giving me hell.

Recent problems: Not a full pierce in the metal, lots of top slag/dross, when it does pierce the exit cut is wavy.

I've read through a lot of the threads and tried to use as much searchfu as I could to figure out what the problem is but it came to no success. The issue is that I've tired many different speeds, pierce delay, pierce heights, cut heights, plunge rates, and voltages. The most successful cut I've had was, 18IPM, 2s, .15in, .15in, 15IPM, and 140V at 120AMP. However, this produces the wavy exit cut; it does produce very little dross either side which I'm happy about. If anyone has any kind of advice PLEASE let me hear it this plasma cutting has stalled me for way to long.

Thank you.

[WSS]

What is the rated mechanized pierce of the 152? If it is rated for 3/4", then you might try to set up some pierce settings something like this:

arc start height: .125"
Pierce height: .22-.25"
Pierce delay: 1.5 to 1.7 sec.
speed to cut height: 5 to 8 ipm
Freeze the torch for small internal (holes) cuts under say 1.25dia. (cut at your arc start height).

Use longer leads, general rule is lead=thickness of plate. You can shorten it up once you can see what is going on and the piercing is solid. Our machine generally limits plasma to 5/8" or 3/4" if it is a short cut file. After that it is oxy/propane for 3/4" to 3"


Make sure your shield has all its holes flowing air and the nozzle is crisp and round. One bad pierce and you gotta shut it down and inspect/clean. The trick is to get out of the way of the blowback. Go as high as needed. You will use an alarming number of consumables until you get the settings just right. Use anti-spatter around the pierces, it helps shed the crater so the torch does not drag on it and cause the dreaded "wave". I use water based anti-spatter diluted with water and a pump up sprayer (8 bucks at Lowes) and coat the whole plate or cut area. It is fast and cheap.

The quality of the cut depends almost entirely on the pierce, if it pierces good and no pierce boogers stick to the nozzle or crater it then the rest of the cut should follow. If you have any topside entry dross, try to scrape it with a burger flipper or putty knife BEFORE the torch comes back around to it, or raise the volts to avoid touching it.

Good luck and happy cutting!

WSS

[evoandyvii]

arc start height: .125"
Pierce height: .22-.25"
Pierce delay: 1.5 to 1.7 sec.
speed to cut height: 5 to 8 ipm
Freeze the torch for small internal (holes) cuts under say 1.25dia. (cut at your arc start height).

Use longer leads, general rule is lead=thickness of plate. You can shorten it up once you can see what is going on and the piercing is solid. Our machine generally limits plasma to 5/8" or 3/4" if it is a short cut file. After that it is oxy/propane for 3/4" to 3"

I used pretty much all the settings you gave me and it made a really nice top cut but the exit cut still isn't remotely straight. I haven't checked the air flow of the nozzle yet and I that could very well be the culprit.

The manual on the TD 152 says pierce is .20 inches for 3/4" it is said to be able to cut 1and a 1/4 steal clean.

The rule of thumb for the lead is gunna come in handy but right now I'm actually just test cutting with 3inch lines trying to get it to cut all the way through consistently and cleanly but it's not doing that very well at this point.



edit: I've got a couple more cuts in and the lines gotten straighter and i think I've about got it dialed in now. THANKS A MILLION WWS really appreciate it. My other question is: there is mucho beveling on the cut. The machine has always seemed to cut like this even on the thinner materials, but it seems to be cutting in at an angle not really straight down any clues as to why?

[Scratch]

Yeah I don't know what you could be doing wrong either... I have just the older version of your machine (TD 151) and I cut right through my 1" easily.
Like I told you, I don't have ATHC but I pierce at about 1/8" and cut at about 1/16". I bring the pierce to pretty much a dead stop to get through it, then bump up the IPM to about 10 I think.... Using full power (100 Amps) and 90A tips, machine torch (the "One Torch"- just like you I think.)

[evoandyvii]

OHHHH mannn so I don't mean to bump this thread back up for no reason but i had to say thank you to everyone that helped. Finally got some money together for a dryer. After a little bit of tweeking to get the settings right my cuts are amazing. I really wanted to thank everyone for there help and the time they took to respond to my issues. I really appreciate it.