Vacuum Pump, continuous run vs on and off

[Anthony Webb]

We have been playing around with alternative pumps to save some money for people looking at building our DIY PNP machine.  Currently we use a really nice (and expensive) GAST vacuum pump, on ebay used ones are over $100.  We brought in a couple others to evaluate that are in more the $10-$30 range.  The one we really like is this:

http://www.robotdigg.com/product/599/Diaphragm+pump+4+desktop+PNP+Machine

It is extremely quiet and seems to have great vacuum as well.  We have been debating whether it is better to start the pump when we connect to the smoothieboard and let the pump run continuously, or, if we should turn on and off the pump with each pick and place operation?  The question becomes it is harder on a pump to start and stop a whole bunch, or hard to have it sucking against the solenoids for most of its life?

Can anyone offer some advice or perspective?

[Jason von Nieda]

Hi Anthony,

I'm not sure one way or the other, but I thought I'd offer up a third option. Instead of switching the pump on and off, wire it to main power so it's always on and then use that spare output to drive an inline solenoid that vents the pump to atmosphere when it's not needed.

Jason

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[Anthony Webb]

Good point Jason, that just might be the best option.

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[Alexander]

There is also one more option: use timeout. When the machine receives pick command it starts the pump for say 10-20 seconds. If this time ends then the pump is turned off. If another pick operation occurs it resets timeout back to 10-20 seconds. So the pump is off when it's really not needed but you don't have to turn it on and off hundreds of times at each pick.

среда, 17 февраля 2016 г., 5:26:54 UTC+3 пользователь Anthony Webb написал:

[Rich Obermeyer]

The spec I saw on that pump showed nearly 2amps of drive current which was surprising since others have been around 400-500mA.  Also the MTBF of that pump was only ~500 hours.  Seems very low to me.

60db noise does not sound extremely quiet either.  I was looking for something in the 45db range.

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[Jason Parmenter]

Rich,  I'm not sure I would classify it as extremely quite either.  It is a nice smooth, low-level hum however.  I did measure the current today from 380mA to 550 mA (no load --> full load) @ 24 V. 

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[Anthony Webb]

Extremely quiet would be relative I guess. I've had 5 or 6 pumps including the cheap ones like the one used on the firepick delta (which was the noisiest of them all) and the more expensive gast pumps and this is the quietest I have tried. If there are others you'd like to have us try send over a link. 

Sent from my iPhone

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[Rich Obermeyer]

Just going by the spec on robotdigg and 2Amps@12volts loaded is a lot.

I did not see the MTBF specified but for that design it will be short.

How much vacuum is required for this application? 

I could not quickly find a better solution.  I will continue to search.

My wife will not allow a 60 db pump to run in our DIY house 😏

I tried with FPD and I was rejected.

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[Daniel Dumitru]

One ideea for pump would be hotair station pump .  (Search on google) 

IT's not that silent but it least a considerable period of time.  More than that with a single triac you can modify debit .

Br,

DAniel

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[Malte R.]

Hi,

please excuse the X-post. I wrote about 1he pump I use and noise insulation here:
https://groups.google.com/d/msg/openpnp/w46THEk0Mjc/ax7yq5IrDwAJ

Pump is about EUR 20-30, it draws about 3amps at 12V. I've used it for > 100 hours now without a problem.

I would like to reiterate how much adding a "storage tank" for low pressure / "vacuum" and high pressure (blow off) has improved the quality of my PnP's pneumatic system.

I basically use steel bottles (similar to swiss-made SIGG drinking bottles) which happen to have an R3/4 thread so I could easily connect the lines to them.

Think of it as a pneumatic capacitor... Similar to the caps in your electronic circuit, it will smoothen out air flow and pressure spikes caused by the compressors cylinders. Look at any household or industrial air compressor - it will also have a tank for sure...

I use a small circuit to monitor the pressure in both the "vacuum" and the "pressure" bottle. The pump is connected via 2/3 valves. Whenever the pressure is above / below threshold + hysteresis, the pump runs. It is rather noisy, that's why I put it into the box. With this insulation its barely audible - the PnP movement is much louder.

When pressure is OK, pump stays silent :-)

Regards
Malte

[Anthony Webb]

Thanks for the suggestion Malte!  I'm going to dig a little deeper into this idea and may hit you up for some advice.

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[Michael Anton]

Has anyone tried putting a vacuum pump inside a vacuum reservoir?  This would also do a good job of isolating the noise, since sound doesn't conduct at all in a total vacuum, and poorly in a partial vacuum.  Then mostly one would just have to worry about conducted noise.  You would just need a hose to the outside of the tank to allow ambient air pressure into the pump.  The only thing I would worry about is heat dissipation, as that will be poor in a vacuum.

Mike