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plasma cutters - anyone know much?


Mark
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Mark, I'll have a bash at answering. Take it with a pinch of salt.

1. There are, as far as I know, 2 starting methods for the arc - much like tig welding. The 'better' method is HF (high frequency) start, which effecively automatically creates a pilotarc for you when you press the button, so you don't need to manually strike an arc between torch and workpiece and then lift off (like an arc welder or scratch-start tig).

In theory, the tip of a plasma shouldn't contact the work piece (like a tig, again). But in order to let the user just lean it on the material and not worry about 'hovering' above the surface, most plasmas have insulated 'drag gun' type heads which mean you can just plonk it on the metal and go, without maintaining manually a stand-off distance for the duration of the cut. Much easier.

I'm kinda guessing that the push start is a combination of having a non-HF machine and a drag tip. I *think* the 'push start' is a sprung contact tip which can be pushed into contact with the metal to start the arc, then by releasing pressure on the torch, the spring will retract the tip sufficiently that it will act as a drag gun and you can just do you cut leaning on the material. This is a guess.

There are no real standards for plasma guns, but lots seem to fit the same spares. My old Portamig (copper transformer, external compressor) has the same torch (pretty much) as my much newer Sureweld inverter/internal compressor jobby.

2. I'm not sure about the sprung bit itself - never encountered one, but I've not doubt at all you can find spares for this one. If not, its only a matter of connecting the air line, power and switch cables to chuck on a new torch. All easily done as you'll see when you take the sides off to give it a clean ;) .

Hope it helps, Al. :) (Hope its right, too! :ph34r: )

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Mark,

I would agree with Al.

We have had both types of plasma cutter at work. IMHO the press button start is the better one, and appears to give fewer problems with tips burning out. you will gain some experience of this type over the weekend :)

As far as costs are concerned, the portable one which we use cost just over £700. It will cut upto 6mm thich mild steel and stainless, so should tackle most Landrover stuff, unless you are building a bomb proof winch cradle :D

You will also need to budget for a small compressor, one of the £60 machine mart jobies would be more than ample.

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Adrian,

I am looking forward to having a go this weekend with your one :D

I have to admit that I won this on eBlag last night, and hence the questions :o

Am pretty certain it won't be operational by the weekend though, but if I have collected it by then, I will bring it over anyway!

Mmmmm plasma... :D

Mark

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Mark I'd expect more than a 4mm cut from 35 amp output. So thats a bonus.

Stumpy - HF start does wear the parts considerably, which explains why your press start torches last longer. Good practice - as I'm sure you know is to minimise HF arc time by getting to the cutting as soon as you can after pressing the GO button!

One point though - I'd honestly be wary of buy too small a compressor. Especially if the capacity is indeed more than 4mm. Not having enough air will severely limit your performance - especially on larger machines (if it is a small cut capacity, you could be ok). Air supply is the single limiting factor on my small unit with the built in compressor.

My larger machine is a 1/2 inch cut, and I'm a bit worried about my large-but-not-huge compressor keeping up...

Cheers, Al.

:)

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Thanks Al, very useful information.

To date my little 7cfm compressor has managed to keep up, but I tend to limit the cutting to relatively short runs.

I do have a compressor upgrade in the pipeline ( no pun intended ), as the little unit will not run my air tools.

Adrian.

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:huh: Are there any bits on your car that you can practice on, rather than starting out on mine??? :huh: GULP!!!

Judging by the info on the project thus far, i'm not sure that there is a great deal of car left to practice on :)

I have some bits of metal you Mark can play with to get your hand in.

How about a convertable ? :D :D

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I found the sevicing and repair costs on inverter type plasmas can be very hard to live with.

The only inverter plasmas i could recomend are sureweld or hypertherm, and even those don't last that long.

After spending nearly 2K in 3 years on my 30A butters inverter plasma i've now given up on it, and am now trying to find a decent solid state one.

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Dan, the inverter type plasmas are the much newer type, right? Just checking, as I don't think the one I have bought is even close to state of the art - basically it's a big transformer as far as I can tell, so i shouldn't come accross the same issues as you have had ... :o

Anyone got a recomendation of what shade goggles to use with plasma? was looking at something around shade 5 - my speedglas helmet only goes down to 9...

just checking ;)

Mark

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Don't worry Mark, yours is a transformer, not an inverter.

Since its not huge Mark, look at the goggles you can get between 3 & 5. Some people even plasma without goggles, but I wouldn't recommend it...

Get the flip up ones with clear lenses behind to save yourself time. ;)

Al.

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Hmm, not sure. You could maybe find some shade 3/4/5 glass and chuck it in a crappy old welding mask for cheapo plasma fun?

You can then wear your glasses underneath.

Al.

EDIT: P.S. I dunno if these are shaded properly, but something like this would be the way to go if you can't use goggles:

http://www.rapidwelding.com/item--Green-Co...ecs--E2SG1.html

Give 'em a ring and find out what shade it is?

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Dan, the inverter type plasmas are the much newer type, right? Just checking, as I don't think the one I have bought is even close to state of the art - basically it's a big transformer as far as I can tell, so i shouldn't come accross the same issues as you have had ... :o

Anyone got a recomendation of what shade goggles to use with plasma? was looking at something around shade 5 - my speedglas helmet only goes down to 9...

just checking ;)

Mark

If you are useing the plasma properly you shouldn't need any shade at all as the arc should be on the other side of the work piece.

Yours sounds like just what i'm after, if you have problems with consumeables you could allways change the gun for a newer type one.

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Hmm, not sure I agree completely. Look at a CNC plasma - you can hardly say its not being done 'properly', but it's not exactly dull on the upper surface.

I know what you mean, it can be that all the sparks / light is coming out the bottom during a cut, but it seems you'll always get flashed or see the light at some point - just enough to ruin your vision temporarily to follow a line. Personally, for this reason, I like to wear goggles.

Speaking of new guns. Does anyone know the difference between a machine torch and a manual one? Anything that can justify the 3x price multiplier...?

Al. :)

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Hmm, not sure I agree completely. Look at a CNC plasma - you can hardly say its not being done 'properly', but it's not exactly dull on the upper surface.

I know what you mean, it can be that all the sparks / light is coming out the bottom during a cut, but it seems you'll always get flashed or see the light at some point - just enough to ruin your vision temporarily to follow a line. Personally, for this reason, I like to wear goggles.

Speaking of new guns. Does anyone know the difference between a machine torch and a manual one? Anything that can justify the 3x price multiplier...?

Al. :)

I can only speak from experiance :)

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Fair enough! Me too.

:)

EDIT for investigation:

I know a plasma arc isn't as bright as a mig arc, or especially a tig arc, but don't you ever get flashed when starting a cut at the edge of a piece of material? I like to get my head pretty well in there (partly cos i can only ever find black marker pens in my garage which don't show up too well on steel...). Same goes for when you're cutting very rough (rusted) or painted steel - far more likely to see the arc in my experience?

Also, when piercing I guess you start with the torch angled and don't just fire up with it perpendicular to the material (correct way)? If so, how can you avoid being flashed? You've got to until the material is penetrated and the cutting proper can begin, no? Also on this point - aren't you afraid of getting molten steel blobs in your eyes? Especially when piercing as its blowing back up at an angle, and not through and out the bottom (yet). Do you just wear clear goggles?

I also wondered what the output amps of your plasma is - maybe if its not a very big one its not so bright? Dunno (not that mine is big - 6mm cut with the Sureweld, and 1/2" with the (new to me) Portamig).

Al :)

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  • 2 weeks later...

Picked up the Plasma cutter in the week, and finally got to play with it today. It seems to work well, apart from the fact that I don't have a suitably rated supply so it keeps blowing thr trips. According to the front panel it needs 21A so I need to get big feed out to the garage...

Some plasma porn:

post-92-1188673135_thumb.jpg

post-92-1188673170_thumb.jpg

post-92-1188673215_thumb.jpg

post-92-1188673258_thumb.jpg

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Fair enough! Me too.

:)

EDIT for investigation:

I know a plasma arc isn't as bright as a mig arc, or especially a tig arc, but don't you ever get flashed when starting a cut at the edge of a piece of material? I like to get my head pretty well in there (partly cos i can only ever find black marker pens in my garage which don't show up too well on steel...). Same goes for when you're cutting very rough (rusted) or painted steel - far more likely to see the arc in my experience?

Also, when piercing I guess you start with the torch angled and don't just fire up with it perpendicular to the material (correct way)? If so, how can you avoid being flashed? You've got to until the material is penetrated and the cutting proper can begin, no? Also on this point - aren't you afraid of getting molten steel blobs in your eyes? Especially when piercing as its blowing back up at an angle, and not through and out the bottom (yet). Do you just wear clear goggles?

I also wondered what the output amps of your plasma is - maybe if its not a very big one its not so bright? Dunno (not that mine is big - 6mm cut with the Sureweld, and 1/2" with the (new to me) Portamig).

Al :)

I use clear safety glasses, and i just position myself so as not to get flashed at the start of cut and when i'm breaking through i just close my eyes and wait for the change in pitch of the compressed air as it breaks through.

My old one is a 30A, and now use a 100A and have no probs with it.

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