Plasma cutting - what am I doing wrong?

[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: