Dodge Posted August 8, 2006 Share Posted August 8, 2006 I am getting ready to buy a plasma cutter. I've never owned one myself but used one at work for years and took air supply requirements for granted. Now that I am going to have to be aware of it I realize I may need to get a bigger compressor. You guys and/ or gals that have a plasma machine; How big is you compressor?? The plasma machine I am looking at requires 270 scfh ;4.5 cfm @ 60 psi. I saw a compressor at HF that claims a rate of 6.0 scfm @ 40 psi - 4.2 scfm @ 115 psi. By doing the math, this seems to cover the range but it only has an 8 gallon tank. Do I need a bigger tank? Whats the difference between cfm and scfm? Same thing?? Pre-thanks for your input :) Quote Link to comment Share on other sites More sharing options...
RBrown Posted August 8, 2006 Share Posted August 8, 2006 Befor i got my plasma cutter i got my compresor first i got a delta from sams club 80 gal 2 stage. it was the bigest at the best price when i got it. you will be better off with a bigger tank and 2 stage that way when the air preshur drops it kicks on and fills back up without you having to stop and wate on it. if you can afford it i would actualy recomend an ingersoll but i have no complants with my delta. also get a air cleaner water seperator not an inline oiler you want as clean of air going through your plasma cutter as possible. Quote Link to comment Share on other sites More sharing options...
plain ol Bill Posted August 8, 2006 Share Posted August 8, 2006 My compressor is putting out 17 CFM @ 90 PSI so I have not run into any air problems. Unless you know for a fact that your air is DRY - DRY - DRY put a coalescing (toilet paper type) filter in line just before you enter the plasma. It will be money well spent as a tiny (itty bitty little thing) water droplet will ruin consumables in a hurry. I have an Esab 550I and love it! Quote Link to comment Share on other sites More sharing options...
Chris Pook Posted August 8, 2006 Share Posted August 8, 2006 X10 on the airdryer. Wet air will make your life miserable and go through lots of tips. Quote Link to comment Share on other sites More sharing options...
Dodge Posted August 9, 2006 Author Share Posted August 9, 2006 Let me rephrase the question. What would be the smallest compressor I could get away with? Would a smaller one, say a 30 gallon tank, just limit the cutting time or would it limit the cutting capacity etc?? Quote Link to comment Share on other sites More sharing options...
J W Bennett Posted August 9, 2006 Share Posted August 9, 2006 Dodge, I have a Hypertherm 380 and I run a 5hp compressor with a 27 Gal tank. As long as I am not running anything else in the shop I have no problems. However if I have a small leak of any kind I will have to wait for it to catch up. It's pretty safe to say it is maxed out. One of these days I'll get a bigger compressor but I get by with this one for now. Being a Jarhead you should be used to getting by on the minimum.LOL Take heed to the filters and dryers, they will save you alot of headaches. JWB Quote Link to comment Share on other sites More sharing options...
Dodge Posted August 9, 2006 Author Share Posted August 9, 2006 JWB, LOL! My cover has been compromised. Improvise, adapt, and overcome!! Yup, Fully aware of moisture and dirt problems and am planning accordingly. Thanks :) Quote Link to comment Share on other sites More sharing options...
Glenn Posted August 9, 2006 Share Posted August 9, 2006 Check on the duty cycle of the air compressor you look at purchasing. You can always use more air for other things. Quote Link to comment Share on other sites More sharing options...
Ten Hammers Posted August 10, 2006 Share Posted August 10, 2006 Scott, will see if this posts. I have a 16 cfm single stage ( 60 gallon). Local farm store it was about $ 500- 8-9 years ago. Keeps up ok for me but sometimes you have to be patient with die grinder. Of course this won't do tractor tires very fast but that wasn't the question. I can shop locally for a price if you wish. Even with gas prices it ain't THAT far and we can compare. Good luck. BTW we can always use some more ships company crew for security ( )..... ALSO, I'd beware of marketing techniques of compressor mfgrs. What I do know is that when a pump is rated at 22 cfm @ 150 psi it means just that. On a 2 stage pump this will suit most die gringer etc needs + plasma and whatever else my shop might need plus. When a mfgr claims that their compressor is rated at 12 cfm at 90 psi and 24 cfm at 45 psi it is my humble opinion that this is a marketing ploy to confuse people into thinking they can have a big cfm rig, just use lower pressure. Somebody please correct me if I'm wrong. I really don't know the difference between Cubic feet ( per ) minute and ( unknown "S ") cfm. sorry. Quote Link to comment Share on other sites More sharing options...
Ellen Posted August 10, 2006 Share Posted August 10, 2006 Definition SCFM -- The term SCFM stands for Standard Cubic Feet Per Minute, referenced to a pre-specified pressure, temperature, and relative humidity. In most cases, SCFM is referenced to 14.7 PSIA, 68°F, and 0% relative humidity. By specifying these parameters, the mass flow of compressed air and gas systems is clearly defined. Quote Link to comment Share on other sites More sharing options...
Dodge Posted August 10, 2006 Author Share Posted August 10, 2006 Ellen, Thanks for clarifiying the scfm / cfm difference. If I understand it correctly then scfm would denote perfect texbook conditions and cfm would denote actual average shop conditions? I know thats probably grossly over simplified;) Quote Link to comment Share on other sites More sharing options...
Ellen Posted August 10, 2006 Share Posted August 10, 2006 Dodge, I think you've got it! Quote Link to comment Share on other sites More sharing options...
Ten Hammers Posted August 11, 2006 Share Posted August 11, 2006 OK I guess my ignorance shows. Can you tell me the reason for posting 2 different cfm ratings ( at different pressures ) ?Northern Industrial Electric Twin-Stack Air Compressor 4.3 Gallon, 2 HP | Electric Powered Air Compressors | Northern Tool + Equipment Quote Link to comment Share on other sites More sharing options...
Ellen Posted August 12, 2006 Share Posted August 12, 2006 Ten Hammers, long time since I studied physics but as I recall, Boyle's Law(s) which cover the behavior of gasses show that volume is inversely related to pressure; i.e. pressure goes up, volume goes down. A practical example of this is a coal forge blower which moves a larger volume of air at a low pressure and works well, vs. trying to manage a coal fire with an air compressor which produces a higher pressure and a lower volume. Sorry if my explanation is not clear, perhaps others can be more lucid on the topic. Quote Link to comment Share on other sites More sharing options...
Dodge Posted August 12, 2006 Author Share Posted August 12, 2006 Steve, Another oversimplified explanation, (kiss;)) might be that they are advertising the high and low end of typical useage. 40 psi being the minimum that most paint sprayers woul require and 90 psi being the highest working pressure that OSHA will allow in the workplace. Just a guess, uneducated at that :) Quote Link to comment Share on other sites More sharing options...
frogvalley Posted August 13, 2006 Share Posted August 13, 2006 Dodge- What plasma cutter are you considering? That would help with the advice. I have a Thermal dynamics CutMaster 38. Its their small unit and will cut up to 1/2or so but works great on 1/4 and 1/8 which are more common sizes to work here in my shop. It runs great off of our painting compressor which is a three horse with a twenty gallon tank. We rarely have to wait for recovery but sometimes do. Not a big problem though. To answer your question more directly, the compressor will make you wait if its too small, we first tested this unit on a smaller one horse and it worked for a minute at a time and then we had to wait. The tank size is important but secondary in my opinion, the recovery time relating to the actual output of the compressor is more important. Quote Link to comment Share on other sites More sharing options...
Dodge Posted August 13, 2006 Author Share Posted August 13, 2006 I bought the Hypertherm powermax 380. Quote Link to comment Share on other sites More sharing options...
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