Plasma cutting - push or pull??

[londonsean69]

Evening all.

I have just got myself a plasma cutter, and was merrily melting bits of metal about 10 mins after getting it out of the box.

I then managed to do a couple of nice, decent cuts, using a bit of 25.3 flat as a guide.

That was on 3mm plate.

My question is, when cutting, do you push or pull?

I found everything a lot nicer when pulling, but on 6mm plate it started to get a bit 'spurty'. Big globs of metal flying around.

Do I need to push forward to get some heat into the next bit of metal, like MIG?

1mm was fun, cutting out silly shapes freehand as fast as I could move the torch!!

Cheers

Sean

 

[Paul.]

It shouldn't matter, the torch should be at 90deg to the work, unlike a mig torch or electrode which slopes, automated plasma profilers change direction all the time, with a manual machine just do what is most comfortable.

 

[londonsean69]

Cheers.

I think what I am doing is not holding it at 90 degress on the thicker stuff, as I get a bit of splashback and clog the tip.

Must get a few of those castle tips, or that little springy bit of wire that keeps the tip off the work

Sean

 

[astro_al]

The crud blowing back at the torch might be related to speed not angle. If your speed increases slightly so that the machine doesn't have time to fully penetrate the bit of metal you are on at that time, then molten metal will be sent (reflected) upwards by the joined metal at the bottom of the cut 'valley'.

You are aiming for a consistent speed at a consistent angle (torch to work angle), and to never rise above the full-penetration speed for a given machine setting / depth of material.

Pull / push - more important is being comfortable and staying consistent for a good finish.

Cheers, Al.

 

[londonsean69]

Right, that makes perfect sense about the crub being blown back up. Basically, it hits the bottom of the channel, rather than flying out the back.

More practice this evening then

Sean

 

[chunkolini]

Make sure you wear eye protection, I have a tiny burn scar on my eyelid from a tiny speck of spatter. Idiot, but a lucky idiot.

Another tip, try and work sat down and have your arm resting on a rail or similar so that you dont get exaggerated wobbles whe cutting freehand. Going freehand I usually push so I can follow a line easily, working to an edge I usually pull. Sometimes.

Chunko'/.

 

[wyn]

Some plasma cutters are not very good when you use a piece of steel as a straight line guide. It may be trying to arc across to it. I have used a thin bit of timber...until it starts to burn.

 

[londonsean69]

Make sure you wear eye protection, I have a tiny burn scar on my eyelid from a tiny speck of spatter. Idiot, but a lucky idiot.

I have an old auto darkening mask that doesn't auto darken anymore. It's Shade 5 and full face, so perfect. Also wear my gauntlets, overalls and steel toecaps.
I value my digits after nearly losing one before!

Another tip, try and work sat down and have your arm resting on a rail or similar so that you dont get exaggerated wobbles whe cutting freehand. Going freehand I usually push so I can follow a line easily, working to an edge I usually pull. Sometimes.

I have shaky hands at the best of times (nerve damage from a diving accident) so tend to wobble a bit anyway. I always brace off of something where possible when welding, this is no different

Some plasma cutters are not very good when you use a piece of steel as a straight line guide. It may be trying to arc across to it. I have used a thin bit of timber...until it starts to burn.

Yeah, I found that out!!
I will probably just use hardboard for templates. I only really have limited use for a plasma, it is a nicety rather than a necessity.
The hardboar will only ever have to last 4 goes at most, currently

I'm building a kit car, and wish I had bought a plasma at the start of the project for cutting out all of the chassis plates!

Cheers for the answers guys

Sean

 

[rtbcomp]

Also you may need a bit more airflow for thicker material.

 

[Hitch]

Can add much more. As already mentioned keep the tip upright. Speed will probably be the problem on 6mm, more so if its close to the machines capacity.If thats the case, the lines in the cut will be quite angled, and sweeping away in the lower few mm of plate.
I use chunko's method. Push on intricate freehand work, more for the ease of seeing round the tip to be able to follow the line. For straight edges, i use a bit of sheet as a guide, it needs to be smooth so the tip doesnt snag, and draw it towards me.

Another thing to do, is do a test cut quickly moving the torch along the intended route to make sure you are in a comfortable position from start to finish.

 

[londonsean69]

Another thing to do, is do a test cut quickly moving the torch along the intended route to make sure you are in a comfortable position from start to finish.

I assume you mean trace out the intended route, without pulling the trigger??

Cheers

Sean

 

[chunkolini]

Good point Hitch, I do that as well, it is really anoying to have to stop mid cut to move your arm, the same applies when laying a long bead of weld. A mate once compared me to the old Geezer in the Tv series Kung Fu, when I was telling him to practice his move without the torch switched on, and started woffling on about the flow of movement etc.

But it does help to make simple flowing movements when doing this stuff, just done set your robes on fire. Also remember to breathe, that used to annoy me, seeing a long cut get wobbly as I ran out of breath then have a spike when I exhaled.

An interesting thing to try is photocopy an outline, stick it on the metal with spraymount and run around it with the torch, great for lettering etc.

Chunko'.

 

[londonsean69]

Also remember to breathe, that used to annoy me, seeing a long cut get wobbly as I ran out of breath then have a spike when I exhaled.

I have to force myself to breathe, it is so easy to just hold your breath, and like you said, get wobbly.

Cheers for all the tips guys

Sean

 

[chunkolini]

Quote an old thread.

''Us welders are we the new mystics?
Spaced out in our own little world, lost from view' watching a tiny spark with a bucket on our head, and no other reference points. A 'safe' world, no worries no hassles that cant be controlled.

I remember a posting on A N other site where one of the old gang described it as ''chasing that elusive blue lady spark''

I was talking to wifey about it, she is all spiritual and into yoga etc.
between us we realised that it is much the same, totally focused, breath slows down, a ritual to escape in, and world can just bog off while you are doing it.

It always amazes me how much disomfort or even pain I can ignore when laying a long weld, 'a spark, on the leg, ow, Ow Ow OW OW carry on as it has stopped'' or Ow Ow OW OW OW yipes *************** that hurt but still finished the weld'' or how much of a distraction I can ignore before the spell gets broken ' Hmm smoky weld, very smoky, hey SMOKEY!! ohmygodI'monfire''.

Or on a really big weld, just how hot it gets, gloves smoking, head cooking, feeling gassed and just get to the end of the line before stopping. Some of my sculpture stuff is gruesome to do, a child sized torso covered in mig weld, cant stop the run or it ruins the effect.

I had a weird moment a few weeks back. My best mate had died horribly, I was waiting for the kick in the guts to come. Laying a series of long welds, and playing the Flaming 'Lips Waiting for Superman' a sad sad song. I cracked up, blubbering like a baby, and didn't even stop what I was doing, just finished the weld. Made a lovely job of it as well.

I can also remember when I first started, it was such a ntense thing that I could not even breath and weld together. You could even see where I had to breath, a tremble in the line as I ran out of oxygen and stop/start.

Bonkers the lot of us.

Chunko'.
http://www.mig-welding.co.uk/forum/showthread.php?t=10037&page=3
If the link works. If it makes any sense.

Chunko'.

 

[mac1]

Hi Sean

Not all plasma's hand torches are designed to "drag cut", some you have to hold off the surface using your own skill, others have a spring or guide that does this & a few have a shield.

If you drag cut unshielded the consumable life is shocking!!

Finally, its always easier if you drag the torch towards you.

Good luck