Miller Spectrum 375 Plasma Cutter

[Pat]

Hi Again,

I have a chance to buy a barely used Miller Spectrum 375 plasma cutter for $750.00. I would really like to have the Spectrum 625 because of the higher duty cycle, but I since I will be on sick leave for another month and actually have time to use the plasma cutter, and don,t have the funds for the 625, I think I will get the 375. I have all the needed wiring to run the cutter but I am not sure about the compressed air. I have an older Sears 2hp air compressor that has a 12 gallon tank on it. I can not find any information (or part number for that matter) that states the capabilities of this compressor. I do use this compressor for my impact wrench and it gives me enough torque for lug nuts. On the other hand when using my air cutoff tool it will draw the air from the tank in a hurry, and the compressor is constantly running. Judging from these examples I have no idea if this compressor is capable of supplying enough air for the plasma cutter. The manual states the the plasma cutter needs the following: Plasma Gas Flow/Pressure 4.5cfm (129 L/min) at 60 PSI (414 kPa). Can someone tell by the examples I provided, or is there any way I can test the output on this compressor. I am hoping for good news because I can't afford a new compressor at this time.....thanks

[Paul B]

I think the cutmate 375 needs 4.5 CFM.

Time your compressor to charge up your tank from empty... note the cutoff pressure and then plug those results into the formula on this website. It should give you an indication. note that the calcuation appears to be linked to the calc above it, so you have to fill it all out to get it to calc properly.

http://www.aircompeq.com/formulas.html

[Fla Jim]

I have a spectrum 375 I use mostly for aluminum. I'm very happy with it. Aluminum looks like it was sheared. If your Sears compressor is the older one with the cast iron compressor, it should be around 6.4 CFM @90 psi And will work with the Spectrum.
I would recommend that you get a "Motor Guard air filter". Moisture is very bad for the consumables. Miller lists it in their calalog, but you can get it cheaper direct. There was some posts previously on the subject. Do a search for motor guard. I run mine on 240 Volts. One of these days when I have time I'm going to make a "plasma buggy stand" for it.

Jim

[grocery_getter]

plasma cutting aluminum

How thick of an aluminum can you cut and still maintain the sheared look with your 375? I work with mainly 1/8 aluminum sheet and wonder if the 375 has enough capacity for this thickness in aluminum. Also when cutting pieces that will be tiged together on the cut edges, do you need to dress up the edge of the cut to get a good strong weld?

I heard that aluminum that is cut using processes involving heat has to have their edges cut or dress up before final welding can be done to maintain their strength. I was reading up on that subject while comparing laser cutting and water jet cutting. Touted as one of the main benefit of cutting up aluminum using WJ process compared to LC.

I have a 625 in mind but was wondering if the 375 will do the job just fine.

[Sberry]

Is this a comp that runs on 120V or 240? If it is 120V Fla Jim is about right. Advertised HP is different than real HP. Aprox 12 amps per hp on 120V, 4 cfm per hp.

[Pat]

Thank you for the responses.

I found the owners manual which stated the following:

Maximum displacement....... 9.6 cfm (272Lm)

7.8 SCFM @ 40 psi (220 slm @ 276 kPa)

6.3 SCFM @ 90 psi (178 slm @ 621 kPa)


Sberry27,

It is 120V. Do you know if SCFM and CFM stand for the same thing, and what does slm and kPa stand for?

Fla Jim,

The compressor is aluminum. This last spring when I changed the compressor oil I noticed that it was about 1/3 low, and there is an oil build up on the outside bottom of the compressor and the outside top of the tank. Also when I drain the condensation from the tank there appears to be a small amount of oil in the water. I was wondering if the motor guard filter you mentioned will address this problem, and could you tell me what you mean by buying the filter direct.

If needed I could replace the compressor pump (unless it would be more cost effective to get a new compressor).

Thank you for your advice. Sorry about all the questions but I want to make sure I don't ruin the plasma cutter or create a safety hazard.

[Stoney]

SCFM=Standard Cubic Feet per Minute at Standard Temperature and Pressure (STP) 14.7 PSIA, 68ºF, 36% RH

SLM=Standard Liters per Minute, divide CFM by .035

kPA=KiloPascals, which is the metric form of measuring pressure.

Stoney

[Fla Jim]

Pat
Sounds like your compressor is getting tired. The motor guard will remove oil, but at the cost of shortened filter life.
You want a M-30 filter or the M-45 kit with two extra spare elements. Go to motorguard.com, they list three dealers in Wisconson.
I live in Florida so humidity is a problem for me, specially in the summer (90 degrees+90% humidity=feels like 180). I have a filter on the output of my compressor, I also put a pre filter ahead of the Motor guard on my plasma cutter.
Go to Harbor freight and get one of their 10 dollar automatic tank drains. It replaces the drain valve on your air tank, T's into the tubing going to the unloader. Everytime the compressor starts or stops the valve bleads a shot from the drain works real slick for 10 bucks. If you get one replace the plastic tubing that comes with it with 1/4" copper and new fittings. If the tank stays drained that should also increase filter life.

Jim

[Sberry]

I have been using Royal Purple compressor oil from my Auto Value auto parts store for my compressors. Synthetic and should make a difference in the life of cheaper comps.

[Pat]

Fla Jim,

Yes the compressor is about 15 years old, and I have gotten quite a bit of use out of it. Thanks for the Motor guard filter and automatic drain guard information. I will be buying and installing these items..................thanks again

[Hobart Expert Kevin]

Pat,
Just to confirm the answer to your question, the Spectrum 375 will have no trouble cutting 1/8" aluminum.

I also don't think you will have a duty cycle problem on the 1/8" material unless you really do alot of cutting. I have done alot of cutting with the 375 on many different materials and thicknesses and have never had a duty cycle issue.

Kevin



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[Fla Jim]

If you get the spectrum, I would also recommend you get the stand off roller guide, (Miller #194-883). Look on page 76 of the 2003 Miller catalog. I can't cut straight worth a hoot. The wheels on the guide are 1.5" from the center of the tip. when you want to make a straight cut, just add 1.5" to your measurement, clamp a straightedge to your stock and follow the guide. Be sure to keep the wheel riding next to the guide. I was so proud of my first cut, I didn't pay enough attention on my next cut, and allowed the roller to curve a nice scallop in the stock. .But life is a learning experience.
You will wonder how you got along without one.
Search the past posts for "plasma Buggy" that is the best cart I've seen, both were excellent jobs. When I get some slack, Im going to bulid one. I have the materials ready.

Jim

[deere_x475guy]

Wait....you also better add for the width of the kerf which gets wider as the tip wears....or you will come up short....

Bob

Originally posted by Fla Jim
If you get the spectrum, I would also recommend you get the stand off roller guide, (Miller #194-883). Look on page 76 of the 2003 Miller catalog. I can't cut straight worth a hoot. The wheels on the guide are 1.5" from the center of the tip. when you want to make a straight cut, just add 1.5" to your measurement, clamp a straightedge to your stock and follow the guide. Be sure to keep the wheel riding next to the guide. I was so proud of my first cut, I didn't pay enough attention on my next cut, and allowed the roller to curve a nice scallop in the stock. .But life is a learning experience.
You will wonder how you got along without one.
Search the past posts for "plasma Buggy" that is the best cart I've seen, both were excellent jobs. When I get some slack, Im going to bulid one. I have the materials ready.

Jim

[Pat]

The 375 should be dropped off later this evening. I can hardly wait to get the sparks flying. I will have to wait until I get the Motor Guard Filter that Fla Jim mentioned, and I already ordered the automatic tank drain from Harbor Freight. Thanks to all who provided help and information.