Plasma cutting vs Oxy/Acetylene

   #1  

nomad

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Why are they still using this?
Plasma cutters mo better no?

 
   #2  

hagrid

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Plasma is restricted in material thickness and the technology is much more complex. And it consumes vast quantities of electricity which restricts portability.

With a $400 oxy/acetylene torch kit you can cut 6" thick mild steel. You're looking at $20K to do that with plasma.
 
   #3  
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Plasma is restricted in material thickness and the technology is much more complex. And it consumes vast quantities of electricity which restricts portability.

With a $400 oxy/acetylene torch kit you can cut 6" thick mild steel. You're looking at $20K to do that with plasma.
Good information. I learned something new today :up:
 
   #4  

maui

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both are good tools, both have their advantages/disadvantages. Hagrid is spot on. I would ad that there are other things you can't really do with a plasma cutter. Also depending on where you are they have very different source requirements. Plasma you need a good power supply and good dry air. A torch has the added benefit of rolling a highly condensed fuel and oxygen source which can make an epic black mark on the ground. I've cut nuts and bolts off of machinery with a torch leaving behind the part I wanted to save. Not sure I could have done that with a plasma cutter.
 
   #5  

hagrid

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both are good tools, both have their advantages/disadvantages. Hagrid is spot on. I would ad that there are other things you can't really do with a plasma cutter. Also depending on where you are they have very different source requirements. Plasma you need a good power supply and good dry air. A torch has the added benefit of rolling a highly condensed fuel and oxygen source which can make an epic black mark on the ground. I've cut nuts and bolts off of machinery with a torch leaving behind the part I wanted to save. Not sure I could have done that with a plasma cutter.
Mah pappy has torch tips for his Harris acetylene torch that are just for scarfing the hades off of rivets.
 
   #6  

hagrid

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Good information. I learned something new today :up:
Too kind!

Another tidbit: oxy/fuel (not just acetylene) requires some skill from the operator to set the proper flame and to keep the torch "in the kerf".

Plasma has one push button (apart from some settings on the power source). Once it jumps the starting arc you have a plasma jet. Move slow enough to blow through the other side.
 
   #7  
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nomad

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Thx Hagrid
So cutting 8 -12 mm plate would take about a 60A plasma cutter?
How big is that compared to two of those heavy bottles?
 
   #8  

Stetson

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I think a set of torches will be my next "big" garage related purchase. I always used to have jobs, or side jobs where I had access to them, but I don't anymore. Primary purpose would be working on old, rusty cars and farm stuff.

I don't know the first thing about plasma cutters, but it sounds like a good way for me to wreck nearby, unrelated parts as I taught myself...
 
   #9  

hagrid

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Thx Hagrid
So cutting 8 -12 mm plate would take about a 60A plasma cutter?
How big is that compared to two of those heavy bottles?
That depends: do you want to cut half inch mild steel with authority or just make it through with enough to spare?

A stout, all-around system that can handle half inch mild steel will probably require three phase current and a pure compressed gas... argon is common.

Three phase current: if we are talking a residential installation then you're fucked. The best you'll do is 220 single phase. That limits you big time.

Compressed gas: pure gasses, particularly the noble variety, transition to the plasma state of matter more efficiently than all other gasses. That means more energy is transferred to the work rather than being consumed just to maintain a state of plasma. Compressed, dry, oil-free air will work but it impacts the cutting thickness of your power source.

Bottom line: household plasma systems are restricted to gauge thickness materials. There isn't enough available input power. On the upside you will be able to cut virtually any metal including stainless steel. Oxy fuel can can cut and weld virtually any thickness of ferritic steel you would encounter as a hobbyist. The down side is you will not cut stainless or any other metal that is non-combustible. Titanium is non-ferritic but cuts readily with oxy/fuel.
 
   #10  

BilletMan

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No shit, hagrid finally contributes what he KNOWS! Fuckin aye, about fucking time. Not ragging on pushrods, just educating the masses...hell yeah!
That depends: do you want to cut half inch mild steel with authority or just make it through with enough to spare?

A stout, all-around system that can handle half inch mild steel will probably require three phase current and a pure compressed gas... argon is common.

Three phase current: if we are talking a residential installation then you're fucked. The best you'll do is 220 single phase. That limits you big time.

Compressed gas: pure gasses, particularly the noble variety, transition to the plasma state of matter more efficiently than all other gasses. That means more energy is transferred to the work rather than being consumed just to maintain a state of plasma. Compressed, dry, oil-free air will work but it impacts the cutting thickness of your power source.

Bottom line: household plasma systems are restricted to gauge thickness materials. There isn't enough available input power. On the upside you will be able to cut virtually any metal including stainless steel. Oxy fuel can can cut and weld virtually any thickness of ferritic steel you would encounter as a hobbyist. The down side is you will not cut stainless or any other metal that is non-combustible. Titanium is non-ferritic but cuts readily with oxy/fuel.
 
   #11  

hagrid

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I lived that technology from 1990 to today. Plasma is very handy and I like it but you need a cherry rig with plenty of input power.

Oxy/acetylene is still my weapon of choice for steels. A deft hand can cut plate and get 99% of the slag from the kerf to blow off with the cutting oxygen for $500 up front. Oxygen and acetylene refills are economical.


If any of yinz go the acetylene route please say something here. Acetylene is terrific but dangerous if mishandled and some of the safety rules are not intuitive.
 
   #12  

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My CNC plasma has a Hypertherm Powermax 85 will cut 1” steel with a wiggle start. Biggest I have cut to date is 1/2 mild and it did a dam good job with a ridiculously clean edge.

That said our company is know for our programming ability and being able to turn just about any logo into metal art. I have found the limitations of the machine and it’s not in the thickness it can cut it’s how fine of detail it can cut.

For that and several other reasons we are considering a laser system. Laser will do stupid fine detail and will cut most metals with a nice tight tolerance of about .002 where as the plasma can be .01 but as much as .02 depending on the material and thickness.
 
   #13  
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Yes. A nice clean edge is important. Thats why I was looking at plasma. It will require 3 phase input but a generator is to hand for that. The gas is the thing thats more of a problem cos delivery and suppliers want accounts and dont like DIY guys
 
   #16  

BilletMan

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I think where hagrid is coming from is a metallurgist's use of said process. I'd imagine that the oxygen and maybe nitrogen in the air you use is a whole lot dirtier/oxidizing than the inert gases....normal folks can't in any way do the inert gas deal....hagrid, tell it...
 
   #17  

BilletMan

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hagrid, don't be a pussy. Twice now, I've asked specific questions and you bail...
 
   #18  

simon520

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I have a Hypertherm 45; the biggest pain in the ass is clean dry air as Hagrid stated. I cheat and use grade E filtered breathing air that my Bauer Junior pumps into scooba tanks. So I drag around a 105 CF steel tank with a regulator. Just a minute’s worth of cutting NOTICEABLY drops tank pressure. iIRC you need 20 CFM which is a huge industrial compressor to run continuously. I can go 5 mins before swapping tNks and I have never needed to have more than 5 mins of cutting time. The 3/16 aluminum I was cutting- I mean it’s almost like it’s curting through a couple inches a second; it is ridiculous.

So plasma cutters will do non-ferrous materials which you can’t do with oxy-fuel.

I have oxygen and propane. Look I’m pretty stupid; I keep gun powder in large quantities in my garage but I just won’t keep an acetylene tank. They fucking acetylene tank it’s just too goddamn unstable I just don’t like it.

Oxy peopane isn’t as hot And uses a shit load more oxygen. You’ll get it I forget the ratio but I think it three times more oxygen to get a neutral flame with propane than acetylene. so your oxygen consumption for a given amount of cutting goes way up but shit that’s it if you start the cut you’re basically blasting oxygen in the kerf and cutting with oxygen alone so for the very few times I’ve ever had to pull out my oxy fuel regulator which I bought super cheap on CL propane has worked just fine.

Btw the concern about The price of consumables with plasma cutting- you will eventually erode the tips which are replaceable/consumable. Apparently if you plunge cut or pierced metal thats harder on the tips that if you just cut from an edge I don’t know I’ve had the machine for three years but don’t detect any noticeable wear so when I bought the machine they gave me three sets of consumables which is probably a lifetime supply for me.

So for a production welding shop or a busy Machine ship yeah you’re going to use Oxy-acetylene and you’re going to need a quality torch the Harris torch with multiple tips and the rosebud tip et cetera . You’ll also need a plasma cutter which will do any metal ferrous or bob-ferrous but will need a pretty large amount of clean dry compressed air. You can get by with a small compressor with a large storage tank but you’ll have to stop frequently for it to recharge the tank. If you’re doing production cut you’ll need a much bigger much more expensive compressor. you can get by with a small compressor with a large storage tank but you’ll have to stop frequently for it to recharge the tank. If you’re doing production cuts you’ll need a much bigger much more expensive compressor
 
   #19  

simon520

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Fucking Siri. It’s not like I have a fucking accent or am a non-native speaker. Took me longer to attempt to clean up that post than if I just typed it out with my two thumbs and there still a shit load of typos and grammatical errors which bug the shit out of me .
 
   #20  

simon520

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No need for “inert gas” for plasma. Fuck, it would kill you dollar wise using argon for that purpose. Use plain compressed air which is near enough 80% nitrogen which is inert enough and cheap.
I just use my scuba compressor Because the majority of the huge cost of those scuba compressors is making them so that they will eventually generate grade E breathable air- the filter filtration and drying systems are way more than you need but will guarantee you get clean dry filtered air.
 
   #21  

simon520

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What you CANNOT have is water in the air. Will destroy tips. So figure out how you’re going to dry the air first. Depending on your application and needs that could be anything from radiators and expansion chambers and water taps to refrigeration units and air dryers which again are expensive.
 
   #22  

Stites

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We pierce all day long, sometimes thousands of times per day. We replace the consumables every few days
 
   #23  

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Serious question Stites. Not tryin to be a dick or anything but it you got a request to cut a 5 foot wide swastika would you do it ?
 
   #27  

maui

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I dunno, I think some of you guys are over thinking this a bit, I have a hypertherm 1000, I plug it into the 50amp 220 that I run my welder on. I run it right off my air compressor. I've cut 3/4" steel with ease.
 
   #30  

maui

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I love those things, way better than the old abrasive style wheels
 
   #31  

Stites

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I love those things, way better than the old abrasive style wheels
Yes I have one for aluminum and one for steel and my saw is also made by evolution.
 
   #35  

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How loud is that? What RPM do you run at? Ideal cutting depth and rate? Automated feed I would assume.
We mainly cut aluminum but I do love the carbide blades while cutting steel because there is virtually no sparks.

It is load, but no louder than cutting with a conventional abrasive blade. I don’t remember the rpm but it’s about 2500-3000.

All cuts are performed by humans, feed rate and depth determine by sound of saw
 
   #36  

maui

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We mainly cut aluminum but I do love the carbide blades while cutting steel because there is virtually no sparks.

It is load, but no louder than cutting with a conventional abrasive blade. I don’t remember the rpm but it’s about 2500-3000.

All cuts are performed by humans, feed rate and depth determine by sound of saw
I use anti wheelie control on mine. I tried traction control but that sucked

I think its actually a lot faster then the old style abrasive saws (3x?) and leaves a way cleaner cut.

Also it's a lot easier on the clean up side. chips instead of dust
 
   #37  

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Late '90s we were using 7 1/2 inch circular saws with carbide tipped blades to cut inch thick aluminum sheet into ~ 18 X 36 inch pieces to be made into door struts for helicopters. Finished part weighed about two ounces. Why it wasn't just a welded piece made from 3/4 X 3/4 x 1/8 angle pieces, who knows?
Coolant - lubricant used was kerosene.
 
   #39  

tinhead

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FWIW those struts were the last thing I ever made for The Defense Industry.
 
   #42  

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I lived that technology from 1990 to today. Plasma is very handy and I like it but you need a cherry rig with plenty of input power.

Oxy/acetylene is still my weapon of choice for steels. A deft hand can cut plate and get 99% of the slag from the kerf to blow off with the cutting oxygen for $500 up front. Oxygen and acetylene refills are economical.


If any of yinz go the acetylene route please say something here. Acetylene is terrific but dangerous if mishandled and some of the safety rules are not intuitive.

lots of great info on this thread!!!

all i can add is oxy-propane is hot enough for me to cast platinum...

acetylene is just so damn dirty... but it's nice and hot and works great on big dirty stuff...

too technical ...?

lasers are pretty clean...need to hook one up to a portable nuclear supply...

perhaps a big ol laser in one of these...
 
   #43  

BusaVeloce

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Serious question Stites. Not tryin to be a dick or anything but it you got a request to cut a 5 foot wide swastika would you do it ?


LOL... i have made a few, in gold ... the most recent one was kind of a fuck up...

since it was cast, i finished the ''better'' side and stamped the imperfect side with the karat stamp.

it was rectified but i am sure the customer was never really happy with it...

if i recall... it did find a happy home on someone else...

i love a happy ending...
 
   #44  

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I have a Makita dry cut saw for steel, it is so much better than the old abrasive cut off wheel. I did manage to knock a tooth off the blade on the saw, still works find. I use it for steel and aluminum. I could put a coolant mister on it if I used it a lot.

I started a cardboard box almost on fire at the junk yard using the abrasive saw. The box was a couple feet away but still started to smolder, burned a hole aboot the size of a softball in it. I let it sit there and cook until someone came back wondering what was burning. I pointed at the box and kept working. Wasn't my job to worry aboot a fire, my tools are insured. If left overnight, it probably would have burned the dump down.
 
   #45  

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We mainly cut aluminum but I do love the carbide blades while cutting steel because there is virtually no sparks.

It is load, but no louder than cutting with a conventional abrasive blade. I don’t remember the rpm but it’s about 2500-3000.

All cuts are performed by humans, feed rate and depth determine by sound of saw
Very interesting. I have used the Elu cutoff saws before, mainly for cutting aluminium extrusions. I forget the size of the blade I used, I still want one for myself, not that I need it much. I wouldn't have thought it would cut though steel. There has to be a limit to the steel hardness, not that I know much about it.

On the aluminium extrusions, using an hydraulic band saw worked just as well, although it did take longer. Just a lot quieter.
 
   #46  

Stites

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Very interesting. I have used the Elu cutoff saws before, mainly for cutting aluminium extrusions. I forget the size of the blade I used, I still want one for myself, not that I need it much. I wouldn't have thought it would cut though steel. There has to be a limit to the steel hardness, not that I know much about it.

On the aluminium extrusions, using an hydraulic band saw worked just as well, although it did take longer. Just a lot quieter.

Way quieter, but extremely slow. WE got rid of our band saw and use the Evolution saw exclusively. If the material is to big for the saw we just have the manufacture cut the material for a very small and reasonable fee. Totally worth it and they cut within .005 for our tight jobs at no additional charge.
 
   #47  

maui

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right tool right job, today I need to cut up some old steel to get rid of, The rusty shit will be tough with the plasma due to poor grounding, the odd shaped shit tough with the chop saw. The torch will be slower then either but not having to switch back and forth, or having to clamp shit down is worth it.
 
   #48  

Master-Cylinder

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Way quieter, but extremely slow. WE got rid of our band saw and use the Evolution saw exclusively. If the material is to big for the saw we just have the manufacture cut the material for a very small and reasonable fee. Totally worth it and they cut within .005 for our tight jobs at no additional charge.

Friend of mind had a good sized sign company, they used a huge radial arm saw to cut the big aluminum extrusions. That saw was a dangerous SOB! There ware a few holes in the wall behind it from stuff that didn't go as planned. I think OHSA made they get rid of it.
 
   #50  

hagrid

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acetylene is just so damn dirty... but it's nice and hot and works great on big dirty stuff...
Acetylene in air generates a prodigious amount of soot, the primary element of which is carbon.

Acetylene and pure oxygen is a zebra of a different stripe. Regardless of which fuel chosen an oxy/fuel torch can produce a neutral or oxidizing flame. But acetylene is the one (that is handy) that can also produce a carburizing and a reducing flame. While archaic these flames have their uses, particularly carburizing.
 
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