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Kimmy Armstrong
03-07-2012, 1:03 PM
I have read through the threads on pumps etc. I now have a GAST DOA-P709-AA which came with my laser. It only puts out ~1.1 cfm, which is not enough. I called GAST and told them what I was looking for ~60 psi, 3.8cfm or 100-110 lpm. They suggested a DAA-P716-EB. When I asked the distributor about the price they said $630 and 4-6 weeks since it is not a stock item. Here's my question- I found this nice little Hakko pond pump

http://www.hakkoairpumps.com/subcat10.html

either the HK80L or the HK100L. Has anyone used pond pumps? Do they work well?

Dan Hintz
03-07-2012, 1:06 PM
From their spec sheet:

Normal Pressure Bar (psi): 0.15 (2.13psi)
You said you wanted 60 psi... that's not going to cut it ;)

Also, you don't need 60psi... that's a really high-pressure stream. My ULS is only spec'd to handle 30psi max, and I usually run it at 10psi for most items.

Kimmy Armstrong
03-07-2012, 1:25 PM
Epilog said it the machine can handle 40psi so maybe perhaps I don't want 60 (that's just what GAST suggested), but I want a quiet (relative) pump that puts out 3.5-4cfm without doing any damage. I don't have a lot of space, it's in my basement, and my husband is upstairs trying to watch TV. What do you think of these pond pumps? Many of the air brush pumps don't have the specs listed or are no larger than what I have.

Rich Harman
03-07-2012, 2:35 PM
I just picked up a brand new Gast 71R642 off eBay for $225. It has so much power that I am going to have to divert some of the air when I cut or engrave lighter items or else they will get blown around the table. Each time a hole is cut out there is a bang heard as the piece is blasted onto the table three inches below (I use a pin table).

Kimmy Armstrong
03-07-2012, 3:12 PM
That was a good deal! I'll keep a look out.

Dan Hintz
03-07-2012, 4:09 PM
What do you think of these pond pumps?
As I said, pumps like those are not designed with high-pressure airstreams in mind... they're meant to support air bubblers and the like. You won't find them with more than a few psi of pressure capability.

Mike Null
03-07-2012, 4:54 PM
do a search for air brush compressors. some of them are very quiet and put out all the air you need--besides you can disconnect it and use it for air brushing.

I love Gast products as they seem to have never ending life but they are pricey.

Neil Pabia
03-07-2012, 5:01 PM
Kimmy, I'm running the same pump that you are, what seems to be the problem with it? Is this something i should be looking out for?

Richard Rumancik
03-07-2012, 6:40 PM
Kimmy, I don't think you really need as much air as you have spec'd.

If you want a quiet compressor and can do a little plumbing and electrical, then a very inexpensive option is to use an old medical oxygen concentrator. (These are used in people's homes if they need oxygen.) They are designed to run 24/7 and are quiet. You can leave it in the cabinet if you have a few square feet of floor space - the cabinet is padded inside to reduce noise. Or if you want you can take it out of the box and use something smaller. You can probably pick up a retired unit at a low price from a medical equipment supplier. That is what I am running - it just purrs. You can bleed off excess air and run continuously, or add a small tank and pressure switch if you want to be fancier. I can get 40 psi - not sure of the flow but way more than I need, probably 2-3 cfm max. I usually run 5-10 psi. (Search images <oxygen concentrator compressor> to see what I mean.)

Mark Sipes
03-07-2012, 7:11 PM
Make sure that the hose running from the compressor is large enough for the distance to the outlet without noticible pressure loss. Hard to imagine but there is friction inside the hose..... My system has a control valve at the compressor exit to reduce the flow for those pesky lite jobs. 1.4psig ( 16psi ) puts out a good stream of air. Medo Linear Compressor Vacuum Air Pump AC0401A-A1110-E1-0511

Rudy Ress
03-08-2012, 8:53 AM
I'd be real concerned about using a medical oxygen concentrator. Normal air has ~20% oxygen, the concentrator will do as it is supposed to and concentrate it to a higher percentage. I would think there is more of a fire potential chance. Remember the fire triangle - oxygen - heat - fuel. Just my thoughts.

john banks
03-08-2012, 2:06 PM
I just picked up a brand new Gast 71R642 off eBay for $225. It has so much power that I am going to have to divert some of the air when I cut or engrave lighter items or else they will get blown around the table. Each time a hole is cut out there is a bang heard as the piece is blasted onto the table three inches below (I use a pin table).

Rich, I received a Sealey today which claimed "noise level 72.1dBa" in the manual but on the machine says "97db LWA" and you cannot hold a conversation next to it. At 3 feet, my iPhone (yes I know it isn't an accurate noise meter) shows 92dB and it is too loud. This noise level 72.1dBa must be at 30 feet with polar bears covering your ears or the noise meter!

Trying to find noise info on this Gast. Have you found any and how is it in your opinion for noise?

Rich Harman
03-08-2012, 4:14 PM
Turning on the air pump increases the SPL in my shop from 58dB to 83dB as reported by the JL Audio iPhone app. The CW5000 is 77dB when in cooling mode, the exhaust fan is 78dB and my DC is 88dB.

All measurement taken at a distance of around 3ft.

Thomas Baranowski
03-14-2012, 9:24 PM
I've used a air brush compressor for 2 years on mine, it has a foot pedal so on cuts I just clamp the pedal. It is quiet enough but who would notice with the blower running anyway :) I like that the blower pulls small pieces out of the laser and love hearing then zip down the vent tube

Richard Rumancik
03-15-2012, 2:51 PM
I'd be real concerned about using a medical oxygen concentrator. Normal air has ~20% oxygen, the concentrator will do as it is supposed to and concentrate it to a higher percentage. I would think there is more of a fire potential chance. Remember the fire triangle - oxygen - heat - fuel. Just my thoughts.

Gee, I guess I should have been more specific - I use the compressor from the oxygen concentrator, not the oxygen output itself. You have to rework the connections to make it suitable for use as an air compressor. An oxygen concentrator hardly has any pressure output at the delivery tube end as you don't need much pressure at all for medical use. I don't know for sure but I suspect it is only about 5 psi. This is probably too low for an air assist.

Anyone who attempts this conversion should have a good understanding of how a compressor system works and be sure to have an appropriate pressure relief value in the system (say 40 psi.) You could take out the Zeolite cannisters altogether. The pressure relief valve on the medical compressor itself might be set too low for use as an air compressor and may need to be changed.

Rudy Ress
03-16-2012, 1:21 PM
Gotcha Richard. Understand now what you were saying.

john banks
03-16-2012, 1:32 PM
Richard, do you think there is a way to alter the pressure relief valve on something like this? http://www.hailea.com/e-hailea/product3/ACO-500.htm

Richard Rumancik
03-17-2012, 12:00 PM
John, I don't see an existing pressure relief valve on this unit. It is rated .045 megapascals and 1 megapascal = 145 psi so it looks like this is a 6.5 psi compressor if I did the arithmetic correctly. Such a low psi compressor could probably be manufactured open-loop i.e. no protection as 6 psi is not likely to cause personal injury or an explosion.

If a compressor tank, hoses, filter etc are all rated at say 200 psi then you might install a pressure relief valve set to say 125 psi. That way if the pump did not switch off or there was some malfunction you would not over-pressure the tank and potentially cause an explosion. Even a hose failure can cause it to whip in someone's face.

If a compressor (like mine) is rated by the manufacturer to put out 50 psi safely, then it is prudent to install a 40 psi or lower value relief valve to protect the compressor and hoses and of course the operator. But if you put a 40 psi relief valve on a 6 psi compressor it would be redundant. It's like putting a 100 amp fuse in a 15 amp circuit. It will never blow - and it will never protect anything. But it won't make your 15 amp circuit more than it already is (or your pump generate more than 6.5 psi.)

My pump had a manufacturer's rating of 50 psi but was used at 20 psi in the oxygen concentrator. So they used a 25 psi relief valve. I bumped it up so I could get more of the pump's capacity.

You can install a relief valve in many locations - for a pump without a tank it is often just installed on a manifold or tee at the exhaust air port. When a tank is used it is sometimes installed on the tank or at the entrance to the tank.

Here is what a relief valve looks like. This is a 125 psi version. Lower ratings are a bit harder to find.

http://www.grainger.com/Grainger/CDI-CONTROL-DEVICES-Variable-Pressure-Relief-4TK26