If space isn't a concern which it sounds like it's not from your comments, then I'd say get the bigger one. Unless you need the portability of the smaller one (versus just a long air hose from the larger one) you'll be happier with the larger compressor because you don't have to listen to it cycling on and off constantly like the smaller one will. Unless you're using the plasma for just really short bursts of time, it's likely to drive you insane listening to the smaller compressor cycling on to keep up with you every few minutes.

The one regret I have with my compressor is not getting an oil model. The oil-less motor one I have is so loud I can't stand to be in the garage with it unless I have the main garage door open. I only use it if I absolutely have to with tools that run constantly (sanders, impact wrench, etc) and the rest of the time I use my little senco hotdog compressor when I'm using a nailer or something else that doesn't require a large volume of air.

So in my opinion, I'd get something that will be cycling on as little as possible, and for that you need the bigger tank.

 

My buddy has a compressor that looks quite similar to the smaller one you posted. I tried doing some cutting at his place using his compressor. After maybe a second of cut the compressor came on. After another second the plasma machine turned off because of the low air sensor. I don't know if they offer different CFMs in that same package, but I would steer clear of that little one.

 

That compressor will run pretty much continuously while you are cutting with the Miller unit. That type of operation is tough on the compressor as it is not built for high duty cycle. If your cuts are short and you are just using the plasma for occasional use....it will likely work fine. Make sure you use a filter that absorbs moisture....like a Motorgard brand.

Actually.....take a look at the Hypertherm Powermax30, it has more power output than the Miller, longer consumable life, and usually can be found for $100 or so less......then you can buy a bigger compressor! Hypertherm builds the torches for Miller, but the new Hypertherm 30 amp torch is a great new design, a generation newer than Millers torch.

Jim

 

Go with the biggest (cfm) one you can afford if buying new. Check around at your local craigsllist for used compressors. Go for a compressor that has oil not oil less. Oil Less tend to make alot of noise and have a much shorter compressor life. Plasma cutters like lots of clean dry air so be sure you also get a "GOOD" water/oil/particle filter.

 

Good information guys! Thank you all. I've narrowed it down now to the bigger unit. As far as buying an "oil" compressor, I am just doing short runs with the plasma cutter.

Also, I'll have to look at the Hypertherm 30 now that it was brought up......tough descisions.....

 

Tank size doesn't matter, it's all about air flow. With enough air flow, you don't even need a tank.

I have essentially the same plasma here, a Hypertherm Powermax 380. I've run it on a few compressors and this is what I've found...

6 cfm or less will make you pull your hair out and throw the compressor as far as you can throw it before you go to the store to buy a bigger one.
8 cfm will make you bored waiting for the compressor to catch up.
10 cfm will 'get you by' but won't make you happy.
12 cfm will make you happy.
15 cfm or more will make you exstatic and jump for joy.

The more air the better!

 

What advantage does a higher cfm compressor provide?

I have a Thomas T-2820ST Compressor and I find it works well for supplying a thermal dynamics 82 plasma cutter. It is an oil less design rated at 5.0 CFM / 100 PSI and seems quieter than most other models I've seen.

http://www.thomasairpac.com/products/airpac/airpac_electric/T-2820ST/t-2820st.jsp

A larger tank will allow the compressor to cycle less frequently.

 

Buying a compressor is like buying marijuana. They are both gateways leading to other possibilities and with that you should consider getting a larger compressor. I think Lowe's and Home Depot sell compressors priced in the low to mid $400 range that would be oil/belt driven with either a 26 gal or 60 gal tank. I bought a Campbell hausfeld comp 20 years ago and its still in my garage running.

 

My thought on this is a matter of useage and CFM/duty cycle.
I had a campbell compressor 1st, died in about a year, moved into a speedair, didn't actually die but couldn't ever keep up. After my frustrations I built a Curtis e-57 head up with a 10 hp three phase motor pulleyed to run as a 7.5. Had it about 18 years now and was one of the best additions ever to my shop. It served all my my needs until I got portable in my brain, which my curtis was certainly not, and I ending up building a portable unit.

A few thoughts on 110-120 volts you are limiting yourself to a 3hp motor. Which will give you the 12 cfm, but no expansion or headroom later, especiaally if you size your pump to that. If you size the pump to 5 HP and run it as a 3hp, you will get better life, and have the option to upgrade the motor later, if you desire a few more cfm.

Not complete units but just the pump only but here is a ebay link to a schultz head :
http://www.ebay.com/itm/SCHULZ-SING...OMPRESSOR-PUMP-2-3-5-HP-/280828412003?pt=LH_DefaultDomain_0&hash=item4162ad8063

Price is right and includes shipping, and my portable is a Schultz and while not this model I am very satisfied with the brand in general. BTW mine is a MSV-30.

Smart move on your part asking questions first. I am not a fan of aluminum air compressor pumps.

 

If It were me I'd consider a large bottle of compressed air for plama chopping. Sure you have to get it filled, but no noise and DRY. Might be cheaper too.

I've not done this so I don't really know.

Cheers

 

If It were me I'd consider a large bottle of compressed air for plama chopping. Sure you have to get it filled, but no noise and DRY. Might be cheaper too.

My dad ran his nail guns off scuba tanks when working in office building where noise was a concern. Nice dry air but more expensive than a compressor.

A larger compressor will make more cfm. Two stage is a must. A large tank allows the air to cool dropping out more moisture. Hot air will carry moisture right through the chemical dryer. A refrigerated dryer works best... but that's another topic.

 

i bought hypertherm because you could drag the torch along your metal, even painted surfaces. You dont have to hold the torch off the surface like you do with the miller. Maybe things have changed now for miller.

Also, when choosing a compressor for my needs, I was able to email hyperthem's customer service and they helped me choose a compressor. I bought a 5.5hp honda gas powered air compressor so i could plug my plasma cutter into my bobcat.

 

Most guys that purchase plasma cutters have other compressed air needs as well. Die grinders, paint sprayers, impact wrenches, filling up pool toys(?). I'd consider not only what the plasma cutter needs but any future requirements.

I have a 5 hp 20 gal unit I bought about 15 years ago. It's OK for the light stuff and seems to run my 60 amp plasma cutter ok (cycles alot but still keeps up) but when I use a die grinder / cuttoff wheel it really bogs down. Thought about getting a sand blast cabinet but no way can I run one w/o a lot more cfm than I have now.

I'd recommend getting the biggest unit you can afford. My next compressor will be at least 15 cfm @ 90 psi.

You didn't mention it but does this compressor / plasma cutter need to be portable?

 

Get an Oil type compressor... DO NOT get an oiless compressor.... easy to tell the difference, oil compressors the motor and compressor pump are seperate units.. I stillis have my craftsman 20 gal, 6.5 HP unit i bought new and is going on 15+ yrs old and it gets plenty of use. I think now its part of the "professional" series however it is well worth the extra expense and get 220V ac if you have the hook up for it.... there was a big class action lawsuit a few years back about bogus CFM claims so now I believe the rated capacities are more accurate.. having just bought a plasma cutter I can't tell you what will be enough.. however I have mine adjusted so it fills to about 140 psi and comes back on at about 110 psi if you do this it will reduce the run time of the compressor if you have the plasma set at 90 psi for example

 

Oh one more thing, consider using 3/8" inch connectors instead of 1/4" connectors, if you have a standard 3/8 hose then the system is bottle necking at the connectors.

 

That 'little' Dewalt compressor is made more for pneumatic nailers and such. Not really for 'shop' use. Skip it for use with the plasma IMHO.

The bigger 15 gallon compressor works OK with a PM30 for 'small' usage. I have just those pieces of equipment. The compressor kicks on but the plasma keeps going just fine, at least for the small/short cuts I've made. Would I want such a set-up for all day long 'industrial' usage? Nope. But the compressor is adequate for small/short cuts with the PM30.

The compressor is also adequate to run an IR 1/2 inch impact wrench to remove lug nuts (air is being used in short bursts), but is NOT adequate to run a die grinder (more sustained air usage and the compressor can't keep up) or any other medium-to-high air demand sustained usage air tool. Believe it or not, a 3/8 inch air ratchet seems to use 'more' air than the 1/2 inch impact does because it runs slower RPM and for a longer period of time. The impact just 'zips' the lug nuts off, where the air ratchet is certainly faster than turning a socket by hand it is sure not as fast as that impact! Something to do with the 10,000 RPM free speed on the impact versus like 150 RPM on the ratchet.

The 15 gallon machine also works OK for filling tires too.

And although DesertRider's comment about the 'true' measure of compressors is the sustained airflow from the compressor pump -is- true as far as sustained usage, more air storage (bigger tank size -and- the pump sized to refill it in a reasonable time frame) does matter. Unless you have a big screw compressor and so much excess air capacity that it is being dumped back to atmosphere, a bigger tank gives you several advantages. It gives you a bigger 'reserve' of air for a tool that uses air in short duration but big 'gulps'. Like an impact wrench. IIRC, the actual airflow through a 'decent' 1/2 inch impact wrench during usage is something like 20-30 CFM. So if you are using an impact pretty much non-stop, you would need at least that much airflow capacity. But if you are just zipping off or on a fastener here and there, you can 'get by' with a much lower CFM compressor by having enough air tank capacity to do the zip-on or zip-off and then the tank refills (the pump comes on) while you move over to the next wheel or object, etc.

A tank is also important because it gives the pump and the compressed air a chance to cool off! Most air compressor pumps and motors are -not- made or rated to run non-stop (big industrial screw compressors not withstanding). They have a duty-cycle where they need to cool-off in between being used. The compressed air also should have a chance to cool off, so that the atmospheric moisture that was IN the air when it was compressed can have a chance to cool off and condense out of the compressed air before the air gets used in the tool/machine. Because when the compressed air expands back to atmospheric pressure in the tool/machine, it WILL cool off and then condense any moisture in the air back into liquid water. And air tools run much better on AIR and not globs of water mashing through them. Not to mention the rust/corrosion that water does to the inside of the tools. Or the mess that water does to say a paint job from a spray gun. Or how fast a plasma tip gets used up when water or wet/damp air is going through it instead of clean dry air.

And DesertRider's comment about "The more air the better" is sooooo true!

Small shop use, one person, intermittent use of air tools IMHO pretty much calls for 10-12 CFM as a -minimum-, and that might need to be higher if you get or want to use any higher air demand tools. Very limited use ( no high demand tools) or 'short' duration use (brief usage of an impact wrench for instance) and you can maybe get by with about 5 CFM and some combination of pressure/tank-size to give you 'burst' capabilty.

As Gayle mentioned, trying to run a tool or application (filling tires to 90 psi when the compressor only goes to 120 psi for instance) that needs a certain psi and a certain flow rate can be futile or frustrating unless you have enough 'overhead' for the compressor to drive the tool. Running a 90 psi app when the compressor only goes to 120 psi is tough, unless you have sooo much pump or a huge tank that the pressure never really drops down much even when the tool/app is sucking down the air. A bigger tank and/or more psi -in- the tank (which are the only two ways to get more air in the tank) give you that 'overhead'.

And skywest, although one -can- use a compressed gas cylinder to feed a plasma, it is usually not cheaper than a compressor. Certainly dry though! And quiet.

Let's say you have an 80 ft3 tank. At a flow rate of 5 CFM, that gives you about 16 minutes of use. Then your cylinder is empty. Then you have to swap out to the next cylinder. Another 16 minutes of use. And so on. So -each- 16 minutes of use would cost you a complete refill at about $30-$40 or so at the LWS. Plain air might be less, that's the approx cost around here for 'welding' gas like argon or nitrogen which is mostly the cost of handling to refill/swap the cylinders and not so much the cost of the gas itself. Not including the purchase cost of the cylinder in the first place. For $30 in electricity you could run that 15 gallon Dewalt compressor for about 66 hours of 'on' time at an electricity rate of $0.25 / kw-hr . That would be about 20,000 ft3 of air from the compressor in that time.

15 amps x 120 v = 1800 watts

$30 / $0.25/kw-hr = 120 kw-hr electricity used

120 kw-hr / 1.8 kw = 66.6667 hours of run time

66.6667 hr x 60 min/hr x 5 ft3/min = 20,000 ft3

Running the air compressor is waaaay less expensive than some compressed gas cylinders.

YMMV based on electricity rates and so forth, but you get the idea.

MHO? Get the biggest air compressor you can fit and afford. More air lets you do, well, more. A 'decent' 60-80 gallon 3-5 HP (real motor HP, not marketing-speak HP. Grrr.) is usually about right for a small/home shop. Mobile use or space or electric power limitations may shift trade-offs around somewhat.

And a decent oil-lube air compressor is usually more durable and quieter than an oil-less air compressor. Just have to make sure the oil is there and clean (change it as recommended in the manual) and the compressor can't be run tipped on its side and run a decent air filter system to keep any oil out of things like the plasma or a spray gun.

And remember that one -can- often manifold multiple compressors as an air source. Not always the desired way to go compared to just having one 'decent' compressor, but sometimes a possible way to run things.

 

That 'little' Dewalt compressor is made more for pneumatic nailers and such. Not really for 'shop' use. Skip it for use with the plasma IMHO.

The bigger 15 gallon compressor works OK with a PM30 for 'small' usage. I have just those pieces of equipment. The compressor kicks on but the plasma keeps going just fine, at least for the small/short cuts I've made. Would I want such a set-up for all day long 'industrial' usage? Nope. But the compressor is adequate for small/short cuts with the PM30.

MoonRise,

Thanks for all your input, as well as everyone else. I DO NOT have a "shop" that I'm using this plasma/compressor combination. Again, I'm just doing "lawn art" for me and the wife. I'm making a wrought iron gate for each side of the house but I'm not on any time constraints.

As far as area in my garage, I'm full! I have very limited space and although I'd like the biggest compressor I could squeeze in there, I'm afraid i'll have to stick with the DeWalt model with the 15 gallon tank and 5.4scfm as I listed above. I won't use the plasma cutter all that much and when I do, it will be for small cuts etc... Again, I'm not welding up Dana axel housings or fabricating ATV trailers.

Also, I've run out of room as far as electrical outlets and amperage goes. I'm getting one 240VAC outlet so trying to run both plasma and a compressor on 220V might be difficult. I have to stick with a 120v compressor. I know the DeWalt will probably kick on more frequently, but when I'm done cutting with the cutter, the compressor shouldn't be that hot (yet.).

Thanks again for everyone's input.

 

A friend of mine owns a compressor shop. And I walk in on him a few times a day. Just to bother him or make him laugh. While I am there, I would say one out of five times, someone walks in, that bought a compressor at Home depot, was told it was the right compressor. But the pressure switch points are burned out.

The reason is the duty cycle. They use it too often for to long a time. As the motor gets warm it draws more amps. Causing bigger break ARC's to be created in the pressure switch points. Burning up the points.

It is that $300.00 price tag that does it for them. They really need a $900.00 compressor as a minimum. The bigger the better.

Then over the years you can add on the automatic tank drain solenoids. And automatic draining regulators and filters. Or even a refrigerated dryer for spray guns or plasma cutters.

Sincerely,


William McCormick

 

If it's just the contacts on the air pressure switch wearing out, you could add a relay that would take the wear and tear off the air pressure switch. And add a suppressor (an MOV or a resistor and capacitor in series across the contacts) if contact arcing is a problem.

 

in so cal you can find 60 gallon compressors that will work with your plasma cutter for less then 500$ used. I went though 3 compressors (5 gallon, 30 gallon, another 30 gallon) before i went and got the 60 gallon. once you have a big *** air compressor, you can also use it to power air tools.

 

I would go with the biggest compressor you can fit and have the money for. i ended up upgrading to a 220 compressor that will catch up to the the use of the plasma.

 

I believe it's Ingersol Rand that dubs compressed air as "The fourth utility". I've had a handful of compressors over the years and my experiences are already presented by desertrider33. When I added a sandblast cabinet to my shop I had to yet again upgrade my compressor. This time I went with an IR rotary screw, 30cfm @90psi all day long, which should last me through to the end
If I were compressor-less today and looking to buy my first, I would head the advice given to me back then which is the same that's being given in this thread, go with the biggest you can afford, else you'll regret it later. I suggest shopping around the net for a quality brand like an IR unit, everyone offers free shipping and if you have a Tractor Supply nearby they keep them in stock. Click here for an example. Also, plan on running a dedicated 220V circuit for the compressor.

Good luck.

 

I use a Lowe's Kobalt air compressor with a 30 gallon tank, twin cylinder cast iron construction.

Its 110V as well with wheels. But its quite heavy compared to the DeWalt products. Its a happy compromise and I use it for my plasma needs and it works just fine. I use it to paint and with impact wrenches. Painting will keep it runny about 70% of the time. But for plasma use, it seems to be just fine, even for larger plasmas unless you are running a CNC.

Check it out here:http://www.lowes.com/pd_221495-14989-LLA1683066_0_?productId=3115861&Ntt=kobalt%20air%20compressor&Ntk=i_products&pl=1&currentURL=/pl__0__s?newSearch=true$Ntt=kobalt%20air%20compressor$y=0$x=0

Did I mention its A LOT quieter than those other ones?

 

These are decent little units for what you would like to do.

http://www.chpower.com/webapp/wcs/stores/servlet/chPrd3_10051_10001_93983_-1_10646_10692_

This is a cast iron sleeved compressor, that is rated at 5,000 hours of life. Eight hours a day for two years approximately.


Sincerely,


William McCormick

 

>>>" I'm getting one 240VAC outlet so trying to run both plasma and a compressor on 220V might be difficult. I have to stick with a 120v compressor. "

Just Fyi - dont be scared away from adding 220V outlets - there is no magic about 220. Same wire as normal - just uses a different breaker and a different outlet is all (2 hots and no common wire). Any electrician or yourself should be able to add a dedicated 220v outlet very cheaply. If the run from the panel is long, 220 is recommended.

 

Might want to check this out

 

Did some digging and Jim Colt has commented on this in the past:

http://weldingweb.com/showthread.php?t=52622

I am math bored and stupid today but a 2500 psi air cylinder would last how long?

 

I am math bored and stupid today but a 2500 psi air cylinder would last how long?

My Dad used scuba tanks because we dove a lot and the dive shop had free air for life. Remember those days. A 3000 psi scuba tank at 80 cf will last 15 to 20 minutes assuming 4 to 5 cfm. DSW runs stuff off scuba tanks so he might chime in. A 250 at 2500 psi with nitrogen would last 50 to 62 minutes.

Is a two stage a must or nice to have?

If you can make 90 psi efficiently on a single stage than your likely ahead. The second stage really heats the air. Generally your better machines are two stage. A two cylinder single stage can make a lot of air.

The real issue is a lot of smaller compressors aren't designed to run non-stop. Beware that aluminum pumps will melt down unless they are given sufficient rest (cool off) time. Same goes for lubrication free units with composite pistons. Most the box store units have splash oil sumps, the better units have pressure lubrication.

Yikes... I just realized this is an OLD thread brought back to life. Beating a dead horse. :laugh: