Plasma cutting - what am I doing wrong?

[Big Barn]

Good stuff Terry. Thanks for the ideas!!!

Do you use a Drag Tip now??

Thanks, Richard. Yes I use the drag tip now, but as you (and others) have noted, the 1/2" wide area of the "cut line" must be free of imperfections for a smooth cut.

I LIKE the drag tip for LONG straight cuts using a guide.

..... BUT I actually prefer dragging the retaining cup shoulder using the NON stand off tip on the smooth surface of my aluminum cutting guide.

For freehand work I prefer using a REGULAR tip as movement is not restricted by the "drag".

Gouging, working on dirty material, situations with excess blowback, and all HEAVIER cuts I do as others have mentioned. I use oxy-acetylene.

 

[TMGT]

I took a picture of some material I have cut with my 45, top is 3/4", middle is 5/8" and bottom is 1/4".
The 3/4" and 5/8" could be cleaner if I had better hand control and slowed down a little. View attachment 504580

 

[sweettractors]

My evaluation on plasma cutters in general are that they are almost useless in a farm shop. For fabrication, using new material, they are great. Ken Sweet

 

[rustydollar]

I have a cheap Chinese Cut 70 plasma with HF, expanded metal and rust and even half an inch of layer water pose no problems. Cuts up to 3/4" nicely and will sever 1 1/4".

I use this machine regularly to cut up rusty old farm equipment, often cutting double clad frames with layers of rust embedded in-between that the sides have been separated, pushed apart from the expanding rust.

On heavy equipment with large rusty nuts I'll split them on both sides making it easy to knock them off.

 

[dragoneggs]

One thing I didn't see mentioned much was gun angle, it doesn't take much to increase the effective thickness of the material a lot. I find this especially true on curved surfaced where your hand gets lazy and doesn't adjust quickly to the angle change.
I've had this problem before with my 45 and finally figured it out, it was most notable on 3/8 and up.

The electrical has already been stated, I would add a small filter, like what's used on automotive paint guns, right before the inlet on the machine. I use them and noticed an improvement in the consumables longevity. That is in addition to a water separator at the machine inlet and one at the compressor outlet.

Yes gun angle was something I was struggling with maintaining because of the curved surface. I noticed the torch (flame) exit angle was changing probably in part by the rough surface and dragging at a consistent speed but also just trying to keep it perpendicular to the surface.

With regard to filters... I think I have that covered. I have a separator at the compressor and the 45XP has a built in filter in the back of the machine.

 

[dragoneggs]

Thank you, Mr. Foster, for correcting that error.


You can easily trash an electric motor from low voltage without ever tripping the breaker. As my neighbor who went through 4 sump pumps in his hard in as many years. Inadequate wring by the previous owner, who also went through sump pumps and never figured it out. :confused2:

This is truly a concern of mine. I don't want to burn up my new expensive 45XP just because of my stupid extension cord. I think I better figure a way to measure the voltage under load.

 

[dragoneggs]

Thanks, Richard. Yes I use the drag tip now, but as you (and others) have noted, the 1/2" wide area of the "cut line" must be free of imperfections for a smooth cut.

I LIKE the drag tip for LONG straight cuts using a guide.

..... BUT I actually prefer dragging the retaining cup shoulder using the NON stand off tip on the smooth surface of my aluminum cutting guide.

For freehand work I prefer using a REGULAR tip as movement is not restricted by the "drag".

Gouging, working on dirty material, situations with excess blowback, and all HEAVIER cuts I do as others have mentioned. I use oxy-acetylene.

With respect to gouging, I have played with this feature on my 45XP and it worked great. I pulled some scrap 1/8in bent up welded angle out of the metal recycling bin that had skip welds holding some reinforcement to sort of box the angle. I wanted to salvage the pieces by removing the skip weld. I used the gouging tip and gouging setting and it basically blew away the weld! It was fun but I did make a mess and one needs to pay attention to what is behind what you are shooting at! ... since I wasn't pointing down!

 

[BukitCase]

" I think I better figure a way to measure the voltage under load. "

Dragon, I gave you a couple options in your other thread (build it yourself) - it was kinda long-winded so you mighta missed it... Steve

 

[yomax4]

I have a Hypertherm 45XP. I haven't done a lot of cutting on it yet but for anything up to 1/4in it is doing fine. My setup isn't ideal as I am running a long extension cord from a dryer circuit. I also have to share the one outlet with both the plasma cutter and air compressor so I have to recharge the compressor by shutting down the cutter often. That said, the problem isn't lack of air pressure.

Today I was shortening my 6ft back blade to be more compatible with my BX. I ran into cutting problems when I tried cutting the cutting edge which is curved and tapered from 1/4in on the ends to 1/2in in the middle. At max power, and going as slow as I could, it wouldn't cut through in one pass when I reached the max thickness. After another pass I severed it, but there was heavy dross and a rough cut. I was using the standard drag tip and I estimate my speed was about 15in/min at 1/2in. The manual says max speed for 1/2in is 30in/min. Any ideas on what I am doing wrong?

Note also there was lots of paint and rust in the cut. At first I thought it was a bad/weak ground. I improved that but no difference. My guess is the extension cord is restricting power. I know the ext. cord is way undersized at 10gauge but I'm not running long cuts. And... yes this is temporary until I can properly rewire my shop adding a dedicated sub panel and several circuits for 110 and 220v outlets. Is the extension cord my problem? I am not tripping the 30amp breaker.

Is the cutting edge hardened steel? Does that make a difference? I am going to try cutting a piece of 1/2in mild steel to compare.

Another thing to consider is getting a set of DC Tongs and clamp them around your ground while cutting to see if you are getting proper amp output. I'm pretty sure that machine would error out if the amps dropped very far or if volts went much below 208. DC tongs are priceless when troubleshooting welder and plasma output. You could even be surprised that the number on the dial isn't as accurate as the tongs. I've seen the dial on all kinds of plasma cutters set at 40 or 50 or 60 amps and the tongs beg to differ either higher or lower. Sometimes as much as 6 amps. If your extension cord is the culprit, The tongs will tell you. Good luck.

 

[BukitCase]

DC tongs - I bought this one about a year and a half ago, least expensive one I could find at the time that would do DC clamp-on amps and other useful stuff -

Extech Instruments MA64 True RMS AC/DC 6A Clamp Meter with Non-Contact Voltage Detector - Voltage Testers - Amazon.com

I originally bought it for just the reasons Yomax mentioned, STILL haven't used it for that :laughing: -

But it ALSO works really well for isolating starter problems on tractors - has 2 ranges AC and 2 for DC, 0-60 and 0-600. You can clamp it on your battery cable AND connect the leads at the battery, then just switch the dial back and forth for amps or battery voltage. Makes it pretty quick to decide if your battery is up to snuff or it's something else... Steve