[TheForge] air compressors revisited.

Sun Apr 26 19:13:45 EDT 2009

Terry-
I have an automated plasma cutter.
It is not, strictly speaking, CNC, but its similar enough in every way  
that counts.
Mine is a 4' x 8' C&G Systems machine, which is optical trace, which  
means it follows a drawing, rather than using a computer to generate  
its path.
However, in terms of electrical and compressed air usage, its the same  
as a CNC model.

I currently run a Thermal Dynamics Pak 75 power supply (thats the  
actual plasma cutter, as opposed to the table and control electronics).
This is a medium sized, commercial plasma cutter- it will "pierce"  
3/4" steel, and reasonably cut 1/2".
I think this machine cost me about $2500 (plasma power supply and  
torch only, not table) about ten years ago. Prices may have fallen a  
bit now, so you get more bang for your buck.

Anyway- when cutting metal with this plasma cutter, my 7 1/2hp,  
3phase, 90 gallon tank compressor can barely keep up. I would estimate  
it is running more than 50% of the time.  I used to have a small, 2 hp  
or so portable compressor, and it will run all the time trying to keep  
up with the plasma cutter.

So for a cnc plasma, I would go with at minimum a 5 hp, if you dont  
mind it running all the time, and, better, a 7 1/2hp or 10 hp.

I also frequently use a cabinet model sandblaster. This requires my  
big compressor to run ALL the time, when using it.
If you plan on doing much blasting, be it soda, glass bead, sand, or  
grit, you want 10hp.

Air grinders and sanders also suck up the air.
I use a 5" DA sander a fair amount- and it probably causes the big  
compressor to run at least 50% to keep up.

These are all single user at a time results- if you are trying to do  
two things at once with air, you definitely need more compressor.

One thing I would look at is the new, smaller, rotary compressors.
Big Blu Air Hammers have been using em lately, as demo machines when  
they are showing off their air hammers.
They are small, powerful, and very cool, but more expensive than  
piston compressors.

Actually, if I were you, I would call up Steve at Big Blu, and talk to  
him in person about compressors. Yes, he sells compressors, but he is  
honest, a real blacksmith, and a very good guy- if he doesnt have the  
right machine for you, he would steer you to who does.
But my guess is, he has a much better handle on what you need  than  
most do.
He sells Ingersoll Rand compressors- high quality, commercial grade,  
made in america.

http://www.bigbluhammer.com/products/air_compressors.htm

Ries

On Apr 26, 2009, at 3:47 PM, terry l. ridder wrote:

Hello mike;

On Sun, 26 Apr 2009, GRAF wrote:

> terry,
> What do YOU intend to run off of the compressor(s)
>

the list of tools that would require compressed air is as follows:

cnc plasma cutter
cnc wood router

spray painting
soda blasting
parts cleaning
various sizes of nail guns
die grinders
air drills
air rachett wrenches
air nibblers
air angle grinders
air hoists

>
> Which are likely to be in use at the same time?
>
> A start off point would be your largest consumption machine at  
> 100%plus
> enough capacity to allow it to cycle within its duty range.
> Build up from there until the pricing gets out of hand. Leave enough
> room and service ports ready to accept another compressor if you  
> need one.
>

i have been reading up on air systems and pneumatic tools. perhaps two
duplex units would be the way to go. the duplex are mainly for
reliability. the chances of both electrical motors or compressor pump
failing at the same time is relatively low. two 20 hp duplex units is
really like having 4, 10 hp air compressors on two air reservoirs that
are piped together. at that point it is the piping size that becomes
critical. my friend paul has suggested that i find an old towed
industrial air compressor and rebuild the diesel engine and the
compressor. he figures it would out last him and i both. one unit that
is on the auction block has an air dryer option installed on it all
ready. the diesel has 650 hours on it. the compressor has 384 hrs since
last rebuild. it is an old ingersoll-rand unit. i really do not like
purchasing ingersoll-rand because they are an offshore company
headquartered in bermuda.  bermuda, had a large role in the 12 yr long
legal nightmare.

do i want to rebuild equipment to be used eventually or do i want to
just have equipment that is ready to use? that is a very good question
which i have not reached an answer yet.

there are times when i think i need to just stop for a while and think
about everything that is going on right now and perhaps rethink just how
i am doing some things. it seems like it is going to take much longer to
get to a usable shop than i ever first imagined. part of that is that
the purpose of the shop has expanded. going back to just being a
whitesmith and blacksmith shop strikes me as the right thing to do. i
can not do everything. i will turn out be a jack-of-all-trades and a
master of none. i would rather be bending metal be it tin or mild steel
than repairing a lift truck for the upteenth time.

>
> Mike Graf
>

-- 
terry l. ridder ><>
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Ries Niemi
Industrial Artist
http://www.riesniemi.com/