Air Source Questions: Spectrum 625 and 375 Extreme.

[Bly]

I have decided on a Miller Spectrum 625 Extreme or 375 Extreme but have a few air source questions. I would rather get the 625 Extreme as it's only $300-$400 more but don't want to have to buy an $800 compressor right now. I plan to only cut up to 1/4" steel in 6" lengths and probably alot of 1/8" steel in 2-3 foot lenghts at the time.

1. How long will an 80 cf tank of nitrogen last? Is there a way to calculate this?I have decided on a Miller Spectrum 625 Extreme or 375 Extreme but have a few air source questions. I would rather get the 625 Extreme as it's only $300-$400 more but don't want to have to buy an $800 compressor right now. I plan to only cut up to 1/4" steel in 6" lengths and probably a lot of 1/8" steel in 2-3 foot lengths at the time.

1. How long will an 80 cf tank of nitrogen last? Is there a way to calculate this?

2. Are there any disadvantages to nitrogen other than the cost?

3. Can I get by with a smaller cfm compressor on the 625... say 4 or 5 cfm? I'm assuming that you would need 6 cfm + 20% for to get the maximum rated cuts (5/8) right but not with the cutting I'll be doing. I have a 2.9 cfm compressor now.

Thanks for the help.

[davedarragh]

Do The Math

I have decided on a Miller Spectrum 625 Extreme or 375 Extreme but have a few air source questions. I would rather get the 625 Extreme as it's only $300-$400 more but don't want to have to buy an $800 compressor right now. I plan to only cut up to 1/4" steel in 6" lengths and probably alot of 1/8" steel in 2-3 foot lenghts at the time.

1. How long will an 80 cf tank of nitrogen last? Is there a way to calculate this?I have decided on a Miller Spectrum 625 Extreme or 375 Extreme but have a few air source questions. I would rather get the 625 Extreme as it's only $300-$400 more but don't want to have to buy an $800 compressor right now. I plan to only cut up to 1/4" steel in 6" lengths and probably a lot of 1/8" steel in 2-3 foot lengths at the time.

1. How long will an 80 cf tank of nitrogen last? Is there a way to calculate this?

2. Are there any disadvantages to nitrogen other than the cost?

3. Can I get by with a smaller cfm compressor on the 625... say 4 or 5 cfm? I'm assuming that you would need 6 cfm + 20% for to get the maximum rated cuts (5/8) right but not with the cutting I'll be doing. I have a 2.9 cfm compressor now.

Thanks for the help.


2. Are there any disadvantages to nitrogen other than the cost?

3. Can I get by with a smaller cfm compressor on the 625... say 4 or 5 cfm? I'm assuming that you would need 6 cfm + 20% for to get the maximum rated cuts (5/8) right but not with the cutting I'll be doing. I have a 2.9 cfm compressor now.

Thanks for the help.

An 80 Cu ftank of N2 or air will provide you with about 13 minutes of "cut" time, with the 625. (80 cu ft divided by 6 CFM).

You need a compressor with a minimum of 1.5 times the input requirements of the plasma. 6 CFM x 1.5 = 9.0.

Hope this answers your questions.

Dave

[Desertrider33]

My Powermax 380 has a minimum compressor cfm rating of 6 cfm @ 90 psi, if I remember right. That number, however, is completely bogus. In my experience, it needs a minimum 12 cfm to be happy with it at all and even then I'm waiting on air and it makes rough cuts on 1/2". It runs great on 15 cfm, no complaints at that level. To get the most from your machine, you'll want 15 cfm or more.

Don't even bother with your 2.9 cfm compressor, the poor thing will be running constantly and the plasma will make rough cuts and keep shutting down for lack of air. That was my experience running mine on my little Porter Cable pancake compressor and I had the high output model of it too, which if I remember right was over 4 cfm. Those little compressors are just not made to supply high demand tools like plasma cutters and sanders/grinders. They do fine with nail guns, staple guns, small impact wrench or hammer, etc that only use a short burst of air at a time. Even impact wrenches and chisel/hammers will give out for lack of air if you run them for longer than a few seconds.

[piniongear]

My HTP 625 Microcut plasma machine is an inverter 40 amp. It requires 4.25 CFM air supply.
My compressor is a Quincy 325, 5 hp 2 stage putting out about 18 CFM at 90 psi, so I have no problem. I calculate the minimum I would need is a 10 CFM compressor to run my plasma.

You are going to have to get yourself a fairly decent compressor to use the plasma. It's just all part of the game.

You may also want to look at getting a really good air drier while you are at it, unless your intention is just make rough cuts, because moisture in the line is going to cause you problems.

The thing is this, although it is more money for the compressor, it is also a tool that you are going to use for other things too............ pg

[SundownIII]

Bly,

Bottom line is you don't have enough air compressor to run "any" plasma.

Nitrogen is an option, but not a really great one. Your question about using an 80 to feed a plasma leads me to question the logic of even buying a plasma at this time. Guys running plasma (mostly in the field) off a nitrogen bottle are using large bottles and it's because of practicality.

Plasma cutters are not "at their best" at doing the cuts you sorta described anyway. As a "cut off tool" there are better options. Those include a dry cut saw, a smaller bandsaw, or even a good chop saw. I would definitely recommend one of these options before you bought a plasma.

I have a large compressor and two plasma cutters (PM 600 & PM 1250) in the shop and they both get used quite a bit. However, I also have a DeWalt chop saw, a Porter-Cable dry cut saw, a Milwaukee portaband, a Milwaukee 8" metal cut saw, and a Wilton 7"x12" bandsaw. All these cutting tools get used about as much as the plasma. Oh yea, there's also the o/a torch.

When it comes to cutting out "shapes/non straight edges", the plasma is the tool of choice. As a "cut off tool", plasma is down the list.

What I'm basically saying is that there are a lot of options that will do the job you describe, for a lot less than a plasma. They may not be as "***y" as a plasma, but they do a good job.

[Bly]

Thanks for the help everyone. Let me clarify what I plan to do with the plasma cutter.

1. I mainly plan to cut up to 16 gauge sheet metal and 1/8 - 1/4 steel and aluminum plate (2-3 foot lengths) to make enclosures / boxes.

2. For making holes in up to 3/8 steel and aluminum for bolts.

3. This is mainly for hobby use.

So is a plasma what I need or are there better tools for this? I'm new to this. I have thought about using a torch but it seems that a plasma cutter would be much easier for a novice, plus I gain the ability to cut aluminum.

I read another forum where someone was using a Miller 375 extreme with a DEWALT 4.5-Gallon 200 PSI (Model: D55146) for $349. It does 5.2 SCFM @ 90 PS. If I choose the 375, would this compressor work for my needs? I'm trying to keep the compressor small as possible for portability. Thanks again for the help.

[davedarragh]

"We Need Plasma!"

For cutting aluminum, you won't do it with a torch. N2 works best for that, and stainless. Just get the biggest bottle of N2 you are able to buy/rent.

For 16 ga. sheet metal, it makes nice clean cuts.

Refills are not that expensive. I think I paid $30 or so for a big bottle.

As far as the unit, it's up to you, but no more than the 625 is over the 375, someday, you'll get a big compressor and you'll be glad you did. If the 625 would have been available when I bought my 375, I would have opted for the 625.

Dave

[Desertrider33]

For making clean holes, use a drill press or a mag drill. Drill press is by far more economical.

For cutting lengths of metal, use a 14" chop saw with abrasive blade for steel and use a wood cutting miter saw with carbide or diamond blade for cutting aluminum, or use a horizontal band saw for both steel and aluminum.

For making minor cuts on steel, use a 4.5" angle grinder with an abrasive cut-off disc, or use a sawzall with a bi-metal blade. Sawzall with bi-metal blade also works good for aluminum. For grinding aluminum to shape, use a 4.5" angle grinder with a sandpaper flap wheel.

Maybe you can find a used shear to cut your sheetmetal. There are lots of deals lately on that kind of metal working equipment as more and more shops go out of business and hobbiests try to cash in some of their seldom used garage toys.

[Bly]

Thanks Dave. Well now I'm back to the 625 extreme with a bottle! Like you said, for the small price difference I'd hate to pass up the 625. Although, the 110 volt option would be nice.

[SundownIII]

Bly,

What type welding machines do you currently have?

You are aware that a plasma cut piece of aluminum still has to be ground for welding (the oxides in the area of the cut have to be removed). This is not the case with a "saw cut".

If you do not have any of the aforementioned cutting equipment (previous post), you need to be thinking along those lines rather than worrying about a plasma. Yea, they're all the rage right now, but many welders/fabricators got by for years without one.

Have you ever used a plasma? If not, see if your LWS can set up a demo. They're great machines to have, but, based on what you've told us, there are better options out there.

[tom37]

Bly,

Before it died I had a Craftsman 6 hp 30 gal compressor. I had to run ALOT. Maybe on 3 minutes and off 45 seconds to a minute. Now I have a 80 gal 2 stage. It was $699.00 with 25% off at the old Cummings Tools. Now it says made in USA, I'm just not sure what parts are made here. I would have went with a big name brand if I was in business but I am hobby only. So it works fine.

I have been cutting quite a bit of light gauge sheet. If its under 1/8" I use my grinder with a metabo slicer cut off wheel always. Its fast and very clean. I have been making boxes and trays, I think somewhat like what you are describing doing. Also if its an edge that I want perfect with very little clean up I use the cut off wheel no matter the thickness, it is a little slower but it sure is pretty.

Just something to think about. You could get 5 HF 4.5" grinders for what you will spend on a decent air filter for the plasma. NOT the blue ones tho. The orange are decent for hobby.

I am not trying to talk you out of a way cool tool, just maybe rethink the whole deal and see what will actually work best.

Tom

[SundownIII]

Tom,

Doesn't seem that the OP wants to hear any counters to the plasma cutter. Oh well, his money.

Personally, I can't imagine having a metal/woodworking shop without a substantial air compressor. My air compressor gets used a whole lot more than either of the two plasmas.

Die grinders, impact wrenches, nailers, cut off tool, air saw, painting, sand blasting, etc, etc. All these would be a no go without the air compressor.

Personally, I'd get a good size compressor, a chop saw, and a grinder with a cut-off wheel long before I worried about a plasma.

Guess the old saying goes here. "You can lead a horse to water, but you can't make him drink".

[tom37]

Sundown, I think you may have left out the most important air compressor job of all.

On the 4th of July when you have ask the neighbor over and over to please stop sending rockets over your house, You simply must have a good compressor to supply the air to the potato cannon so you can adjust the sights against the said neighbors front door.

Sorry to get off topic but I couldn't resist.

Tom

[davedarragh]

Plasma Requirements

Bly: You mentioned "portability" regarding an air compressor, so one can only surmize you plan on doing mobile work. In echoing Sundown, you never stated what welding equipment you have. If you plan on being mobile, you'll need a good 10,000 watt generator (like a Bobcat or Trailblazer) to run the 625. 5000 watts will run the 375.

Not knowing your budget, just recommending the 625 and endless bottles of Nitrogen may be somewhat misleading. If portability is in your future, a power source also needs consideration as well as a viable source of transportation.

We answer questions based on the original poster's desire, regarding specific equipment, not knowing their end intentions, and ultimate goals.

Just trying to help you see the "Big Picture" as opposed to a page in a catalog.

Dave

[Desertrider33]

If you want to go mobile with the plasma, you'll need a substantial gasoline powered air compressor, and that's even more money than a substantial shop compressor, in addition to the substantial sized generator to run the plasma.

How do I know this? I use the plasma out on the welding truck when required and that is the equipment needed to operate it in the field.

You don't seem to be too interested in listening to the old hands here so I guess do what you want, all the best of luck to you.