Air assist using refrigerator compressor

[Graham Symns]

I have been doing some searching regarding the above.
Bill Cunningham (12-30-07) made mention of testing one to 300lbs !
My question is :
Has anybody trialled a unit like this and if so would they like to give an update on their experiences.ie longevity etc
What I'm looking for is quietness of operation and the usual fun of organising a nice ,quiet and technically appropriate level of functionality out of what is usually scrapped.In a word re-cycling.
Any input would be appreciated.

Regards Graham

[Gary Bernat]

I worked in the A/C and refrigeraton business for 16 years. These compressors have oil that will get pumped through out the system for lubing and also the referants also cool the compressor down. So if you use a ref compressor you may burn up the compressor motor or over heat it as well. Hope this helps out little bit!

[Lee DeRaud]

I worked in the A/C and refrigeraton business for 16 years. These compressors have oil that will get pumped through out the system for lubing and also the referants also cool the compressor down. So if you use a ref compressor you may burn up the compressor motor or over heat it as well.I was wondering about that when this subject came up. Dunno about the ones used in refrigerators/freezers, but automotive A/C compressors really don't like running "dry".

[paul mott]

Hi Graham,

I use a refrigerator compressor for the air assist on a small milling machine that I have (it blows the chips out of the way, clears the cutting path and provides some cooling to the work). It does have an internal oil bath and some oil mist is always present in the expelled air (not a bad thing here).

I certainly would not want oil mist anywhere near my laser focus lens and so use an aquarium oil less pump for the air assist on the laser machine. These pumps come in various sizes and are quiet in operation they are also extremely cheap (made in China). Incidentally, it cost less than my focus lens which is precious.

Paul.

http://www.cooperman.talktalk.net/files/27_files/image624.jpg

[Graham Symns]

Hello Paul,

Thanks for the reply.
I've seen this pump of yours before and I would be very interested in having the contact details for this unit.

Hello Gary,

I've had a look on the internet and you certainly make me wonder about my re-cycling zeal.
It's the same old story this DIY stuff isn't it?
But you have to keep on trying!

Regards

[paul mott]

Hi Graham,

I can't post a link (without upsetting Mike) but if you ebay search for 'piston air pump' you will turn up a shed full.

Paul.

[James Terry]

This seems like an interesting choice of description: Magnetic piston air pump (http://webglider.com/link/?id=v). This has got to be nothing more than a diaphragm style right?

And then the question: why would one choose diaphragm over piston?

I think what you want is an oil-less piston pump (http://webglider.com/link/?id=w); perhaps dual piston. You can do a search for second-hand medical air pumps which can be a good choice. The one I have is dual piston and labeled as medical.

http://www.sawmillcreek.org/showpost.php?p=1456594&postcount=5

Sound levels: http://www.youtube.com/watch?v=cBAKFx9QDcg

[Dan Hintz]

Diaphragms are used over piston when you don't want to contaminate the airstream...

[Mike Null]

Paul

Don't worry about upsetting me. But forum rules prohibit ebay links so I just follow orders.

[Bill Cunningham]

The Refridge compressor I used was actually out of a home chest type freezer. This was also close to 40 years ago, so available compressors now may or may not be similar to what I used. The one I had was round, and seemed to be incased in a metal dome (upper and lower part) that was spot welded together all around the horizontal seam so I was not able to pull it apart to see what was in it.. As for quiet? Perhaps when it was a sealed unit pumping freon, it was a lot quieter, but thinking back, it probably had the same noise level as a 1hp blower/vaccume (sawdust type).. I think I killed it when I wondered if it needed lubrication of some kind, and I pumped some HP compressor oil into the intake line.. It lost a lot of life right after that, and I just turfed it out.. I've worked on all types of High pressure compressors from the little Cornelius 3000 psi to the Ingersol Rand 5000 psi 6R51 And many in between, but never knew how this one worked..Piston/Diaphram/Vane??? Who knows...

[Gary Bernat]

Most all new ref compressor have pistons. Bigger compressor have screw style. All older comressor I am positive are piston.

[Graham Symns]

Hello all,
I have experienced some difficulty in tracing out the refrigerator disposal chain in an effort to acquire the compressor.
I spoke to the manager at our Super Shed which is part of the city council's waste re-cycling retailer.
She is interested in getting more refrigerator components into the re-cyling system ....won't be happening for a couple of months.
Tried ringing the local servicing companies with little effect.
Rang a major appliance manufacturer and got a price for a new non CFC compressor..NZ$168 + GST (= sales tax)..not bad for a new item I suppose.
I intend to keep on with my enquiries in this side.
I also have thought of using a car air-conditioning compressor from the local car wrecker...seems that this might be a good idea in respect of being able to run it at the lowest RPM which will provide the most useful PSI and flow rate.
Compared to a refigerator compressor it is a quite compact item and probably is very sturdy in its design and quiet.
Has any any comments on the viability of the car air conditioner compressor?
I look forward to your ,as usual, useful comments.

Regards Graham

[Martin Boekers]

It might take a little searching this forum, but I believed that a while back
someone posted about success with small, quiet and cheap pump
that was used in nail salons for and airbrushing nails.

Maybe someone can shed more light on this.

Marty

[Lee DeRaud]

Has any any comments on the viability of the car air conditioner compressor?The compressor might be compact and quiet, but the engine that normally drives it...er, not so much.:eek::p

On a more serious note, as I mentioned before, these widgets really don't like running dry. And yes, I realize they're starting to use electric A/C compressors on some cars, particularly hybrids, running off some non-standard high-voltage DC supply (43V?). I shudder to think how much one of those costs.

[Dan Hintz]

Marty,

I believe Dee is who you are thinking of... she uses a compressor marketed to nail salons.

[Joe De Medeiros]

Marty,

I believe Dee is who you are thinking of... she uses a compressor marketed to nail salons.

I've seen those, they are just standard air brush compressors, like the iwata, or the badger branded ones.

[Graham Symns]

Hi Lee,

I apologise for not having absorbed what you said about car a/c compressors requiring lubrication.
I went back to re-read all the posts to check.
For all that would an oil filter not remove all the oil and if not what percentage would one remove?
As to the enegy to drive one wouldn't a 1/4 HP electric motor say with a 2:1 speed reduction pulley provide enough power?
By the by I have had a look at all the air brush type compressors and they do look to be quite suitable but getting my hands on one let alone
trying to get it by "she who must be obeyed" could be interesting.http://www.sawmillcreek.org/images/icons/icon12.gif

Regards all

[Lee DeRaud]

I apologise for not having absorbed what you said about car a/c compressors requiring lubrication.
I went back to re-read all the posts to check.
For all that would an oil filter not remove all the oil and if not what percentage would one remove?As I understand it, in a car A/C system (and possibly other sorts of refrigeration equipment), the lubricant is carried through the system by the coolant: it's a closed system. When using this as a air-assist compressor, it's an open system: room air in, compressed air out. So the problem isn't so much removing the oil, it's getting it in there in the first place.

As to the enegy to drive one wouldn't a 1/4 HP electric motor say with a 2:1 speed reduction pulley provide enough power?I'm under the impression that a typical A/C compressor uses several horsepower from the car's engine under normal operation. How much you would end up needing for this application, I certainly don't have a definitive answer, but I'd think 1HP+ would be a reasonable minimum starting point. As far as the speed is concerned, on every car A/C I've ever looked at, the compressor pulley is smaller than the crankshaft pulley...do the math.

Far be it from me to discourage anyone's MacGyver fantasies, but this sounds like a whole lot more trouble than it's worth.

[Mike Null]

Lee is correct. These are all sealed systems. The liklihood of them working for any reasonable period of time as an air compressor is very doubtful.

There a federal regulations regarding the disposal of freon (hfc) which was used in the older compressors. You must be licensed. The old refrigerant which, if I recall correctly, was Freon 34, was banned some time back.

Lee is also right that this is more trouble than it's worth.

[Richard Rumancik]

I agree with James Terry's comment regarding the use of a compressor used in medical equipment for air assist. If you want an inexpensive option on the surplus market look for a used or scrap oxygen concentrator. These units are designed for home oxygen therapy. They often have dual piston oil-less compressors which are quiet, as they are used in residences. You can strip out the compressor and re-package it or keep it in the original housing. It will need rewiring, and re-plumbing of the pneumatics. I would suggest adding a pressure control switch and a small tank but I suppose it could be run continuously if you had a relief valve. I have modified one to turn-on at 20 psi and turn-off at 40 psi; it feeds a tank which then goes to a desiccator, filter, regulator etc. I have it beside my laser and it is quiet. (There might be some quiet airbrush compressors available, but my airbrush compressor is much noiser than this unit.)

If you call a local company that sells oxygen concentrators they may have some obsolete units that are being scrapped that could be picked up for a low price. (Google "oxygen concentrator" images if you wish to see what an oxygen concentrator looks like.)

[Joe De Medeiros]

I agree with James Terry's comment regarding the use of a compressor used in medical equipment for air assist. If you want an inexpensive option on the surplus market look for a used or scrap oxygen concentrator. These units are designed for home oxygen therapy. They often have dual piston oil-less compressors which are quiet, as they are used in residences. You can strip out the compressor and re-package it or keep it in the original housing. It will need rewiring, and re-plumbing of the pneumatics. I would suggest adding a pressure control switch and a small tank but I suppose it could be run continuously if you had a relief valve. I have modified one to turn-on at 20 psi and turn-off at 40 psi; it feeds a tank which then goes to a desiccator, filter, regulator etc. I have it beside my laser and it is quiet. (There might be some quiet airbrush compressors available, but my airbrush compressor is much noiser than this unit.)

If you call a local company that sells oxygen concentrators they may have some obsolete units that are being scrapped that could be picked up for a low price. (Google "oxygen concentrator" images if you wish to see what an oxygen concentrator looks like.)

That's what I use to power my glass torches, and they are very quite.

[Graham Symns]

This post is directed at Paul Mott.

In your post of 08-18-2010 you showed a picture of an air pump showing 25W on the carton for its power consumption.

Are you able to tell me its flow rate?

Is the air pump you show adequate for your laser and if so what is the laser you are running ie make and type?

Would you in hindsight now go for a higher flow rate?

I have since my last post located, in New Zealand, a source of this sort of pump.

The ones available have the following specs:

25 litres/min ...16W
100 " ....90W
115 " ....160W

By the way my laser is an Epilog 32EX 75W and I cannot find out the flow-rate recommended for this machine...Can anyone tell me?

I would welcome any advice you can give.

I should also say that based on the advice given I have abandoned the idea of using a refrigerator compressor and would like to thank all who have given freely of their advice.

Regards Graham

[paul mott]

Graham,

The pump is rated at 45 ltr/min but my tubing and reduction at the lens nozzle (1.5mm dia) will reduce this considerably. I cut a lot of acrylic and the flowrate has to be reduced so this is more than adequate for my purposes (the airflow is only there to protect the focus lens and not to cool the work).

I would suggest that if you are cutting wood then a larger size of this type of pump may be more useful (you can, after all, always reduce the flowrate if necessary).

Paul.

[Graham Symns]

Hi Paul,

Thanks for your information...most helpful.

I take from your comments that the flow rate of your pump is satisfactory for your purposes.

Just for interest sake the prices for the pumps I mentioned are:
25 l/min........NZ$45
100l/min.........NZ$95
115l/min........NZ$135
which all look reasonable to me in terms of pricing.

So taking your advice it would appear that the 100l/min would have the most useful flow rate ,and best pricing as well, for my purposes.

The work I do ranges from mylar film to 8mm acrylic to 12mm MDF.

Would you let me know what the power of your laser is?
Have you a manufacturers recommended flow rate?

Regards Graham

[paul mott]

Hi Graham,

The Mylar film and 8mm Acrylic is no problem.

I have never tried to cut 12mm MDF but I would think that a lot of power would be required and probably a lot of air assist as well.
I think you perhaps need to find the air requirements from someone that actually cuts this stuff before choosing the pump.

(It probably depends on the glue/resin used to make the MDF but I would have thought that Nitrogen would be far more productive than high volumes of air but, as I said, I have not tried it).

Paul.

nb. My machine is homebuilt so I have no manufacturers information.

[Robert Walters]

When I hit Harbor Freight yesterday, I picked up one of these air brush compressors #93657 (on sale for $59.99)...

http://www.harborfreight.com/1-8-eighth-hp-40-psi-oilless-airbrush-compressor-93657.html

It's rated at 0.5 CFM, but when I just place my finger over the hose, I can immediately build up the pressure to 60 PSI then it shuts off.

I need to play with it a bit more, but I seriously doubt that it has enough CFM to be used for air assist, but it is VERY quiet.

What make/models of air assist compressors is everyone else using and what do you think of it? Be sure to include details so we can build a nice little comparison list.