Plasma cutting - what am I doing wrong?

[dragoneggs]

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.

 

[All In A Days Work]

I'm not an expert but I'm with you on the extension cord being the problem. 1/2" stuff is pretty thick, I would think you would need full amps with your cutter to make a clean cut.

 

[sweettractors]

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.

I have the same problem with my Hypertherm 45. It is almost a waste of time to try to cut painted/rusty farm equipment metal at 1/2 thickness without excessive prep work. By the time, I prep a piece for the Hypertherm 45 to cut, I can have the job completed with the reliable oxy/acetylene torch. Ken Sweet

 

[ovrszd]

Mark,

I use a Miller 625 Spectrum. It's rated capacity is 5/8" at 12 ipm. The manual says it requires 30 amp and minimum wire size of 10 gauge. At a glance it appears your cutter is similarly rated. I don't consider a Plasma Cutter as having a high demand of input current. I've used mine at several locations because it's so easily transported. I've ran it on 100ft of 10 gauge cord with no noticeable difference in performance.

Air quality on the other hand is critical. Consumable's lifespan can be greatly changed by air quality. Takes a good air compressor to keep up with a Plasma Cutter. After a minute or two of cutting if your compressor is running non-stop it heats up. So it's pumping hot air into your distribution system where it cools as it goes to the Cutter. Now you have condensation in the air supply. A Cutter does not like moisture and again eats your consumables.

If I'm cutting 5/8" I clean the metal. I also calm myself and go slow. I've cut several grader cutter edges 58" thick. I go slower than 12 ipm. I watch the ejected sparks. If they begin to "lean" rearward and not go straight thru the metal, I'm going too fast. That's where very clean metal helps. Takes the jerkiness out of the tip movement.

Like Ken, if it's a dirty/rusty project that I'm not concerned about beauty on I fire up the torch.

Also I learned early on you can ruin a tip in a very short time. Especially if going too fast and not letting the heat blow out the backside. If at any time you aren't cutting all the way thru, all of the heat is coming back to your tip.

The normal indication of tip damage is the cut not being straight thru, might be cutting to the right or left even though the gun is held correctly against the metal. I'll use a damaged tip if I'm not needing a pretty cut. But if building something precise or wanting a finished cut I change tips.

Read the manual concerning the tip and electrode. My manual clearly describes how to inspect them and when they should be replaced. Again, this is all in regards to quality of cut desired.

I have a "spare consumable parts" kit with several electrodes and tips as well as one of each of the other parts such a Drag Shield, Swirl Ring, etc. I'm 90 minute drive from the nearest supplier. Not in the mood to spend 3 hours going after a part when I'm all wound up in a project.....

 

[ovrszd]

Crappy, rainy day outside so I'll dig thru my iron pile for examples of cuts.

Here's the first I found. 1/2" mild steel. Excuse the quality of a couple of these, for some reason I couldn't get my phone camera to focus on the subject....

This first pic is an example of a bad tip. Notice how it didn't cut thru the flatbar at a 90 degree angle. The cut is "leaning". That's a typical result of a worn tip and/or electrode. Also notice the amount of slag. That's caused by going too fast.

These two pics are perfect examples of a bad operator (me)......

This pic better illustrates the speed problem. Notice how my cut is leaning and curved rather than straight thru the metal. I was in a hurry, obviously.

 

[ovrszd]

Here's a couple more examples.

First is 1/8". Using a guide. Probably not a new tip but at least a good one. Notice cut angles and minimal slag. Better speed control. Have no idea how fast I was going, but moving right along, faster than cutting with a torch.

This pic is 1/4" metal. Again, speed control was pretty good. Minimal work required to have a finished edge. What this cut displays is the result of cutting metal that's not smooth. Look closely at the cut and you'll see imperfections. These were caused by the roughness of the metal. Caused the tip to not travel smoothly. If this had been a new, smooth piece of metal, those imperfections wouldn't have been there.

 

[k0ua]

Good pix, and good tutorial Richard.. Thanks..

 

[ovrszd]

Good pix, and good tutorial Richard.. Thanks..

I show my inadequacies without reserve.....

 

[sd455dan]

Dug out some of mine, the cut quality does have a lot to do with how steady of rate you can keep the torch moving- obviously I had some problems with the controlling movement.


One thing that has helped me improve ( lately ) is to watch the sparks exiting the bottom of the cut, there is a sweet spot that the plasma exits that seems to correspond with a good cut.
A really smooth straight edge with enough side height has been helpful to and also keeping the torch body as square as possible while moving along the cut line.

below the ugliest cut I have ever made:laughing:

 

[ovrszd]

Several years ago when I first got a Plasma Cutter I was involved in a discussion here on TBN about their use. A member, can't remember who, said "Every time your heart beats a Plasma Cutter has a wiggle in the cut". He was joking but not by much. Try making a cut without a guide.