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

 

[jb1390]

It's odd to me the number of people that are commenting on having difficulty cutting painted/dirty/rusty metal with their plasma. I have a hypertherm 45xp, and the cutter doesn't really seem to care about the surface condition - can't really tell the difference cutting painted or bare metal. Now, if you're trying to get a really nice cut with a straight edge, a rough surface will be harder to drag against at a constant rate of speed. However, for free hand cutting which is adequate for 98% of the repairs/modifications that I do, I don't have an issue.

If the rust is really thick, then it doesn't cut great with the plasma. However, I find that's even worse with oxy - since oxy actually burns the metal, doesn't just melt it like a plasma.

Tip condition and tip speed/angle are the most important parameters. With a new tip, I can get pretty decent cuts on 5/8" material. With worn tips, sometimes 3/8" is tough. And if I'm trying to get a nice cut, I run the torch along the straight edge etc before powering it, to make sure I'm in a comfortable position for the cut, and to make sure there are no rough spots that would mess up my travel rate.

 

[ovrszd]

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

Very nice cuts. I see nothing wrong with those. Using a Drag Tip? Using a Guide?

 

[ovrszd]

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.

Impressive. Is "Chinese Cut 70" the name of your cutter? Do you have any pics? Your examples are very impressive!!!!

 

[TMGT]

Very nice cuts. I see nothing wrong with those. Using a Drag Tip? Using a Guide?

3/4 was freehand, 5/8 and 1/4 were with a guide I believe, I just grabbed a couple peices i had in the shop to show what the 45 can do on thicker material.
All were done with the std. sheilded/drag tip.

 

[ovrszd]

3/4 was freehand, 5/8 and 1/4 were with a guide I believe, I just grabbed a couple peices i had in the shop to show what the 45 can do on thicker material.
All were done with the std. sheilded/drag tip.

Thanks for the update. Man, you have sooooo much steadier hand than I!!!!! Good stuff!!!!!

 

[dragoneggs]

Thanks Yomax and Steve, that DC tong tool might be my next purchase! I have always eye'd them in the hardware store but really didn't know how much I should pay and what brand, etc. Seems they vary all over in price. I imagine it depends on power/amp rating? I guess I have more research to do.

P.S. Steve I did cruise through your earlier suggestions but it sounded like a two man job and not sure I want to involve my better half if possible.

 

[rustydollar]

Impressive. Is "Chinese Cut 70" the name of your cutter? Do you have any pics? Your examples are very impressive!!!!

Looks like the Cut 70 has been discontinued, they now offer an 80 amp machine also I mistakingly said the machine had HF when in fact it is called ( Pilot Arc ). I sold my plasma cutter but will be soon buying this new model.

Cutting heavy scrap with plenty of amperage I would get about two hours from a consumable, cutting light metal 1/4" to 1/2" about 4 hours, the nice thing is that the consumables are inexpensive if you purchase off of fleabay by the 100 lot.

Here is the new machine in Cdn dollars, PowerPlasma 80S PowerPlasma 8S Plasma Cutters | Everlast Welders

 

[rustydollar]

Here's a listing for the Cut 70 http://http://www.ebay.ca/itm/SIMADRE-Pilot-Arc-70-Amp-Plasma-Cutter-1-Clean-Cut-Easily-w-25-Pilot-Arc-Tips-/161357269610?hash=item2591a48a6a:m:myVTW-BCcCNLOju3cDKKJrw

 

[BukitCase]

"it sounded like a two man job and not sure I want to involve my better half if possible." I can identify; my wife's the "beta tester" in the family - if ANYONE on the planet can find a "bug" in ANYTHING, it's her :laughing:

But, if you were to FIRST build the SHORTEST version of a "power strip" for your cart that you would use, you would have a way to insert meter probes in ONE of the receptacles and your PM45xp in the other - then, any normal DMM could be used for voltage - just check first with NO load, then push the RANGE button to lock it in that range (otherwise it will drive you NUTS trying to read it) - then, take a thicker piece of scrap, set it up for a cut, and with the drag tips it would be easy to start a cut, look away from the torch long enough to read the voltage and you're DONE...

All the cords I mentioned before give me multiple outlets at the 2 locations I normally use for welding stuff so I can plug 2 welders AND the plasma in (at either location) without further extension cords, or in extreme cases I can add the 85 footer with TWO plugs - a simpler way would be a shorter cord with multiple outlets on your cart, then maybe later just a 1 in/1 out extension cord to add in for longer reach.

My reason for the shorter cord is twofold - one, less crap to trip over - two, a bit less voltage drop to add to your already questionable drop for test purposes. But since the NEW cords will hopefully NOT be #10, I would NOT make the multi-outlet cord so short it isn't gonna be usable for your proposed changes in the shop area...

Of course you would STILL have to wire your expanded shop area with enough juice for your needs - I currently (pun intended ) have a 60 amp circuit to the front of my garage, and both "local" area POWER strips run off that - my 5 horse/80 gallon compressor pulls 23 amps running, and I've often been welding at around 200 amps while the compressor's running (same circuit) with no problems at all - 21 CFM at full pressure, then a pre-regulator(my compressor shuts off at 175 psi, pre-regulator set for 110psi)/prefilter/Motorgard - tips last a looooong time with this setup.

Just something to think about... Steve

 

[dragoneggs]

"it sounded like a two man job and not sure I want to involve my better half if possible." I can identify; my wife's the "beta tester" in the family - if ANYONE on the planet can find a "bug" in ANYTHING, it's her :laughing:

But, if you were to FIRST build the SHORTEST version of a "power strip" for your cart that you would use, you would have a way to insert meter probes in ONE of the receptacles and your PM45xp in the other - then, any normal DMM could be used for voltage - just check first with NO load, then push the RANGE button to lock it in that range (otherwise it will drive you NUTS trying to read it) - then, take a thicker piece of scrap, set it up for a cut, and with the drag tips it would be easy to start a cut, look away from the torch long enough to read the voltage and you're DONE...

All the cords I mentioned before give me multiple outlets at the 2 locations I normally use for welding stuff so I can plug 2 welders AND the plasma in (at either location) without further extension cords, or in extreme cases I can add the 85 footer with TWO plugs - a simpler way would be a shorter cord with multiple outlets on your cart, then maybe later just a 1 in/1 out extension cord to add in for longer reach.

My reason for the shorter cord is twofold - one, less crap to trip over - two, a bit less voltage drop to add to your already questionable drop for test purposes. But since the NEW cords will hopefully NOT be #10, I would NOT make the multi-outlet cord so short it isn't gonna be usable for your proposed changes in the shop area...

Of course you would STILL have to wire your expanded shop area with enough juice for your needs - I currently (pun intended ) have a 60 amp circuit to the front of my garage, and both "local" area POWER strips run off that - my 5 horse/80 gallon compressor pulls 23 amps running, and I've often been welding at around 200 amps while the compressor's running (same circuit) with no problems at all - 21 CFM at full pressure, then a pre-regulator(my compressor shuts off at 175 psi, pre-regulator set for 110psi)/prefilter/Motorgard - tips last a looooong time with this setup.

Just something to think about... Steve

Wow Steve! Thank you... I think you have launched me into the right direction going forward and not having to step backward. A whole lot of great info for my situation. A short double outlet extension is now on my 'proyect' list and moving up fast! :drink:

As long as I don't have to use my sandblast cabinet and my plasma cutter at the same time I think I will suffice! :laughing: Thanks again. :thumbsup: