Plasma Cutters - what don't I know?

[Gecko]

So my well used 48kg 140A transformer stick welder has given way to a cheap chinese(?) 220A Stick/TIG/ Plasma inverter box (8kg).
I've only clocked an hour on plasma cutters, so don't really know what I don't know about them.
Apparently mine has been supplied with a PT-31 type plasma torch, but I don't know if this is a good thing or not.
Does anyone have an opinion of what I have or should replace it with?

 

[V8Druid]

So my well used 48kg 140A transformer stick welder has given way to a cheap chinese(?) 220A Stick/TIG/ Plasma inverter box (8kg).
I've only clocked an hour on plasma cutters, so don't really know what I don't know about them.
Apparently mine has been supplied with a PT-31 type plasma torch, but I don't know if this is a good thing or not.
Does anyone have an opinion of what I have or should replace it with?

looks pretty std for this sort of thing ... double ended electrode ... consumables're cheap enough ..... same sort of torch as is on Alex's little unit i cut the swallows out with ... clean nozzle and it cuts sweet enough in 3mm S/steel .... 10mm MS is beyond it .... does 6mm just... ultra steady hand required for anything fancy
PT-31 Air Plasma Cutting Torch Head Body 20072: Amazon.co.uk: Garden & Outdoors

 

[Bucket on wheels]

The nett and YouTube is your friend here, if you don't have any that can show and teach you

https://m.roadkillcustoms.com/plasma-cutting-101/
http://forum.weldingtipsandtricks.com/viewtopic.php?f=2&t=2898

https://beginnerweldingguide.com/how-to-use-a-plasma-cutter/
How to Use a Plasma Cutter
When you first get into metalworking it can be pretty overwhelming. There are tons of principles and practices to learn for you to actually become good at metalworking… there are a few machines and tools you will need to master.

The rest of this article you find in the link Above

 

[Gecko]

Thanks for the replies.

.. clean nozzle and it cuts sweet enough in 3mm S/steel .... 10mm MS is beyond it .... does 6mm just... ultra steady hand required for anything fancy

The instructions claim it'll cut 16mm, but I struggled cutting 10mm. Got through, but ahaf the cut was ragged (suspect that was me).
The torch shown has the "extended" nozzle which is what mine came with, but twice as long as the replacements I ordered before realising there is a difference!
These are the short/normal nozzles (the electrodes are also shorter, so presumably shorter life too)

Both work fine, but the trainer-wheels and circle guide seem to be setup to use the longer nozzle.

There are tons of principles and practices to learn for you to actually become good at metalworking…

Very true. I'm not a beginner (quite competent with oxy), but decided to swap the bottle rental for the plasma.
Just watched the first vid - after the oxy, dragging the tip doesn't come naturally!

The first job out of the box was to cut 20mm holes in the 10mm plate. I used a 25mm hole saw to make a template in a piece of 1/4" 3-ply. I got my four holes and was rather pleased with the result. The ply showed a fair amount of scaring, but would have lasted longer if I'd needed it.

 

[V8Druid]

Thanks for the replies.

The instructions claim it'll cut 16mm, but I struggled cutting 10mm. Got through, but ahaf the cut was ragged (suspect that was me).
The torch shown has the "extended" nozzle which is what mine came with, but twice as long as the replacements I ordered before realising there is a difference!
These are the short/normal nozzles (the electrodes are also shorter, so presumably shorter life too)
View attachment 20503
Both work fine, but the trainer-wheels and circle guide seem to be setup to use the longer nozzle.


Very true. I'm not a beginner (quite competent with oxy), but decided to swap the bottle rental for the plasma.
Just watched the first vid - after the oxy, dragging the tip doesn't come naturally!

The first job out of the box was to cut 20mm holes in the 10mm plate. I used a 25mm hole saw to make a template in a piece of 1/4" 3-ply. I got my four holes and was rather pleased with the result. The ply showed a fair amount of scaring, but would have lasted longer if I'd needed it.

my technique for 50mm services holes in UBs .... 'cept I found MDF lasts a lot longer and using a 130A torch, needed 20mm thick templates .... .... hardboard'd probably do a fair job with those little torch's tips

a clean cut in 16mm is gonna need a good 70+A

the centre of the inner electrode is hafnium from memory and is only a limited depth .. once it's become a semi-spherical hollow it'll not cut anywhere near as well as when it's fresh out the box, but'll continue to cut 'til it's almost exhausted

Plasma Cutting Consumables: What, Why, and How Long Do They Last? (espritautomation.com)

 

[Bucket on wheels]

These are the short/normal nozzles (the electrodes are also shorter, so presumably shorter life too)
View attachment 20503

The electrodes on the plasma cutter do not wear like that in the length you get a small crater in the front of the electrodes and when that crater has become deep enough about 0.8 - 1.2 mm then you have to replace the electrodes. How deep you can wear the electrode varies from manufacturer to manufacturer so my numbers are only approx

 

[Quattromike]

Also the cleaner you can get the parent metal for cutting the longer the consumables will last.

 

[V8Druid]

Also the cleaner you can get the parent metal for cutting the longer the consumables will last.

absolutely .... powdery rust kills nozzles quick

 

[V8Druid]

I first used a Plasma in the mid 80's ... rented a unit for a S/steel job I got dropped in my lap - big curved dummy window lintels in a local shopping centre, that'd been made too wide and needed 40mm trimming off the 12mm brick carrying curved surface ... back then the cutting gas was nitrogen/CO2 and each bottle needed a heater in the line to pre-heat the 40ish PSI coming out the gauges .... was quite a performance to set it all up ........ we don't know we're born these days with simple compressed air as the cutting gas

also need to remember that the compressed air needs to be dry @Gecko so water separator is essential and air pressure needs to be right

 

[Rob65]

As Druid has mentioned dry air is essential. If your air has even the slightest hint of moisture in it the electrodes and tips don’t last long at all.

A water separator is a good start but follow that up with a desiccant filter if you can.

My desiccant filter is a 3ft long piece of 2 inch dia pipe filled with silica gel crystals with a couple of felt wads at each end.

I have a 40amp machine which can just about cut 3/8 inch plate which i think is about typical.

 

[V8Druid]

As Druid has mentioned dry air is essential. If your air has even the slightest hint of moisture in it the electrodes and tips don’t last long at all.

A water separator is a good start but follow that up with a desiccant filter if you can.

My desiccant filter is a 3ft long piece of 2 inch dia pipe filled with silica gel crystals with a couple of felt wads at each end.

I have a 40amp machine which can just about cut 3/8 inch plate which i think is about typical.

how do you dry the silica gel @Rob65 .... and yeh, 'bout the right level of expectations for a 40 amper for a clean severance IMHDO

 

[Rob65]

I find the gel at the inlet end gets wet very quickly but the gel at the outlet stays dry for quite a lot of hours cutting time. I nicked the design from a drier that Harbour Freight in the USA used to sell. They are the American equivalent of out Machine Mart.

When it needs drying, spread it on a metal tray, wait until ‘her wot must be obeyed’ goes out and get it in the oven for an hour or so. Simples.
Rob

 

[Bucket on wheels]

With my hypertherm 45xp I cut 20mm ok 30mm goes but it does not look nice

 

[V8Druid]

With my hypertherm 45xp I cut 20mm ok 30mm goes but it does not look nice

jeeeeeeezus that is slow ..... and i am amazed TBH Frank

 

[Gecko]

the inner electrode is hafnium from memory

I'd noticed the 'different' material on the tip of the electrode - now I understand, thanks.

Hafnium - the stuff Haflinger's are made from!

I'm just running the reg/separator supplied with the machine so far. Not expecting a big issue in an Oz summer, but I'll add a second separator at least for winter.

The machine will do 60A on the plasma.

As for the air pressure - I need to play with it to get a feel,

 

[CPS]

I have a 70amp SIP it cuts 20mm clean and will cut 30mm..... well butcher 30mm

 

[V8Druid]

I have a 70amp SIP it cuts 20mm clean and will cut 30mm..... well butcher 30mm

as I would expect Aiden ..... I've a 130A and that slices 32mm ... clean

I'd noticed the 'different' material on the tip of the electrode - now I understand, thanks.

Hafnium - the stuff Haflinger's are made from!
View attachment 20518

I'm just running the reg/separator supplied with the machine so far. Not expecting a big issue in an Oz summer, but I'll add a second separator at least for winter.

The machine will do 60A on the plasma.

As for the air pressure - I need to play with it to get a feel,

that explains their bomb proof rep.
60 A is a decent amount to play with
air pressure is usually circa 7.5 BAR on most I've encountered

 

[Gecko]

I've seen the nozzle and electrode are available either in plain copper or nickle plated. Any difference in life span?

 

[V8Druid]

I've seen the nozzle and electrode are available either in plain copper or nickle plated. Any difference in life span?

never used a nickel plated one Boyo ...... can't imagine the plating'll last long anyway

 

[Quattromike]

We’re looking at the possibility of getting a profile table next year with both plasma and oxy heads, probably up to 15mm on plasma and above with the oxy/fuel. Still not decided which one. There are a few to choose from, swift cut and kerf and the likes. Will need to do plenty research before hand.