Spindle purge air - dedicated small compressor

Mike RzMachine · Jun 8, 2020

Im setting up my new to me robodrill and was wondering if anyone has set up a small 1hp quiet compressor to provide spindle purge air at the 50-70psi required at the machine.

My thought is that my bigger compressed cycles on and off to pump up to 125psi and then regulates down to 50 psi so lots of wasted energy and some extra wear and tear on the bigger compressor.

My first thought was a rotary vane pump like a vacuum pump as they are so quiet but I don't think they can provide the volume required. Second thought is one of the newer quiet compressors. The 1/2hp-1hp units are fairly quiet and look to all be the same or similar, California air tools/hf/senco.

Has anyone tried this?

Mike

ChipSplitter · Jun 8, 2020

Just put in a massive tank. Like a 1000 gallon propane pig.

13engines · Jun 8, 2020

I'll second the idea of adding another tank to the large compressor. That little compressor, if it can keep up at all, will likely run for long periods if not nearly constantly. No reciprocating type air compressor is designed to do either of those things. Only the screw types are.

Mike RzMachine · Jun 8, 2020

I completely agree that a low end compressor wouldn't last long running continuously at 125psi, I was wondering how long one would last if kept at around 50 psi and maybe add a small cooling fan.

Or maybe I just need to build an outside shed for the compressor.

norb · Jun 8, 2020

Been there, done that. No way a little compressor will keep up. It will beat itself to death. Take my advice and spend the money for a small screw compressor. They are quiet and will last. When I started my shop about 15 years ago,money was tight so I tried using a cheap($350.00 dewalt from a big box store). I burned up 5 of them in a couple of years just using them for the air purge on a machine. The noise was maddening. I learned my lesson and bought a 5 hp kaiser with a seperate huge air tank and an air dryer and never looked back. I need to add a jig grinder to my shop and the 5hp kaiser will not be enough but I can add another Kaiser into the system and just change the set point when it comes on.

Cole2534 · Jun 8, 2020

ChipSplitter said:
Just put in a massive tank. Like a 1000 gallon propane pig.

It'll cycle less frequently, but for a much longer duration. Compressors (recip especially) tend to be sized on a duty cycle and adding 15x storage is definitely going to jack up that calc.

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Robert R · Jun 9, 2020

Mike RzMachine;3564000 My first thought was a rotary vane pump like a vacuum pump as they are so quiet but I don't think they can provide the volume required. Second thought is one of the newer quiet compressors. The 1/2hp-1hp units are fairly quiet and look to all be the same or similar said:
The carbon vane rotary air compressors are designed for continuous duty. The only wear parts are the vanes which are inexpensive and easy to replace. The compressors made by Gast have a maximum output pressure of 10 PSI. There may be other manufacturers which make multiple stage vane compressors.

There are also small diaphragm air compressors that are designed to run continuously. The only wear part is the rubber diaphrgam.
The Gast compressor has a maximum output pressure of 60 psi at 2. CFM. These models could also be used as vacuum pumps by connecting to the inlet port.

A rocking piston pump is similar in design to the diaphragm pump. They use a short stroke piston with a fixed rubber seal to the cylinder wall. There is a 4. cfm 100 psi 3/4 HP model shown in the catalog.

In humid weather you will also need a air dryer. If the required CFM is small a desiccant air dryer would work, The desiccant is inexpensive to replace or you can reuse it by baking it in a oven. The color change of the desiccant will signal when it is time to bake or replace.

trochoidalpath · Jun 9, 2020

I have a 1 hp CAT 10010LFDC. It cannot keep up with a Speedio doing anything even remotely intensive, but it's fairly quiet for a piston compressor and is low maintenance.

That compressor makes 3.0 CFM at 90 PSI. If your spindle air purge draws 1 CFM, you'll draw the 10 gallon tank from 90 PSI to 70 PSI in a touch under 2 minutes. The compressor will run for 55 seconds to refill the tank to 90 PSI. That is a 35% duty cycle, so you would probably be okay.

I feel like if I was in your shoes, I'd add more receiver capacity and let the bigger compressor do its work (assuming it's a decent industrial compressor with a high duty cycle).

Cole2534 · Jun 9, 2020

Robert R said:
The carbon vane rotary air compressors are designed for continuous duty. The only wear parts are the vanes which are inexpensive and easy to replace. The compressors made by Gast have a maximum output pressure of 10 PSI. There may be other manufacturers which make multiple stage vane compressors.

For $500, that may be a good option if 10psi would handle the needs.

aarongough · Jun 9, 2020

I use a small oil-less rotary vane pump as the air source for the air blast to clear chips when cutting dry in my VMC and have been very happy with it. It was an eBay score for around $300 (i think) and I have done zero maintenance on it so far. It runs close to 8 hours a day 5 days a week and has done for the last few years.

They don't have a huge ability to generate pressure, but if high pressure is not needed then they will certainly generate a large volume of air at a relatively low pressure for cheap. I'm sure I have saved more than $300 in electricity costs over the time I've been using it.

Mike RzMachine · Jun 13, 2020

Aaron,
Can you provide a manufacturer and model for the rotary vane pump you use? I'm interested to see what I can find in that realm. I got a refrigerated air dryer anticipating this purge flow but the compressor cycling (mainly the deafening blow off valve) is making me lose my mind.

Also looking at 5 hp rotary screws but that looks to be a future purchase.

Thanks,
Mike

aarongough · Jun 13, 2020

Mike RzMachine said:
Aaron,
Can you provide a manufacturer and model for the rotary vane pump you use? I'm interested to see what I can find in that realm. I got a refrigerated air dryer anticipating this purge flow but the compressor cycling (mainly the deafening blow off valve) is making me lose my mind.

Also looking at 5 hp rotary screws but that looks to be a future purchase.

Thanks,
Mike

Sure mate! Here are the photos of the nameplates on the rotary vane pump that I have:

I believe the 'Thomas' nameplate has the actual part number on it.

Honestly look into the scroll compressor that Eastwood has started selling. Price is much more realistic than what a new screw compressor goes for and at least one other member here seems to have had good experience with that unit so far.

-A

Cole2534 · Jun 14, 2020

aarongough said:
Honestly look into the scroll compressor that Eastwood has started selling. Price is much more realistic than what a new screw compressor goes for and at least one other member here seems to have had good experience with that unit so far.

-A

That'd be me, and I'm really liking the unit. It did have one hiccup recently, the pressure-trol didnt start the unit when it should have. I cycled the on/off switch and it's been great since.

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Mike RzMachine · Jun 16, 2020

Thanks for the info. I have a vacuum pump I'm going to try, as my spindle purge pressure is only 10-13psi. This points to the thought that a 1/3 hp pump can keep up continuously in place of a several hp compressor running at a duty cycle that averages 1 hp due to compressing air to 125psi just to regulate it down to ~12 again. I also found a spindle purge time out setting I'm going to try out. I'm thinking it won't bug me as much when I get cutting with this mill and spend less time setting up with the spindle off.

Mike

aarongough · Jun 16, 2020

Mike RzMachine said:
Thanks for the info. I have a vacuum pump I'm going to try, as my spindle purge pressure is only 10-13psi. This points to the thought that a 1/3 hp pump can keep up continuously in place of a several hp compressor running at a duty cycle that averages 1 hp due to compressing air to 125psi just to regulate it down to ~12 again. I also found a spindle purge time out setting I'm going to try out. I'm thinking it won't bug me as much when I get cutting with this mill and spend less time setting up with the spindle off.

Mike

Just make sure it's an oil-less pump... The reason being that oil type rotary vane vacuum pumps will blow an oil mist out of their exhaust/pressure port when operated near atmospheric pressure. Not sure if that oil mist would be bad for the interior of the spindle, but I imagine it has the potential to cause issues.

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