Vacuum Solenoid Valves

[dave]

Solenoid valves

Hi guys, I am after some solenoid valves. anyone know the part number of Liteplacers original part.

Anyone got any recommendations otherwise. Money is no problem really, we rather not budget, I need two I think. One to shut the line off when no object is picked so we dont lose pressure. Another to allow the vacuum to escape to drop parts.

I really want a good brand. I dont mind paying £50 each for them.

I am building a whole vacuum compressor. TZ712P pump will be stick to 3L airbrush tank I found on ebay. I use a SMC ZSE30AF digital pressure meter to control the tank pressure pump, hopefully my vacuum pump will automatically turn off some of the time like when not in use.

If this turns out to be to loud I might try this via a mains relay. .
http://www.ebay.co.uk/itm/Airbrush-Mini ... Sw9mFWF6X9


I am guessing everything will work. If anyone has input or thinks my idea is just stupid please help.

[mrandt]

Hi Dave,

instead of two separate valves you may also go for a so called 2/3 valve - which connects one input to either of two outputs (or one output to either one of two inputs).

Not all valves are suitable for vacuum so you better check the data sheet or ask manufacturer. The sealing material seems to play a role, I noticed that most vacuum compatible valves use "Viton" seals.

Also, the orrifice should be large enough to allow sufficient flow of air.

I use a bunch of the following valve types and am reasonably happy with those:
https://www.esska-tech.co.uk/esska_eng_ ... 52M1824V00
https://www.esska-tech.co.uk/esska_eng_ ... 13490.html

EDIT: Esska also has distribution centers in other countries, e.g. in Finland and Germany. Change the region before you order

Note: Even though these are labelled "for compressed air", they work fine with negative pressure (vacuum). Merchant seems to use that term to distinguish air valves from vapor or fluid types.

Brian Dorey also posted some helpful info here:
http://briandorey.com/post/smc-vacuum-a ... grade.aspx

Another hint: The farther away from the needle you mount the valve, the longer the tubing and the more "pneumatic capacitance" you add to your setup. You probably have to increases pickup and placement times then or take more complex counter-measures such as compressed air to quickly equalize the pressure level in the tube.

Regards
Malte

[JuKu]

SC0726G, 24V DC, from here: http://www.skoocom.com/. It is a three way valve, when the vacuum is released the needle is connected to outside, to drop the part. But I don't think It really fulfills your spec "I really want a good brand. I dont mind paying £50 each for them." Besides, last time I talked to them, the minimum order was 144 pieces; I got samples only after I told them about my intentions.

[dave]

Juku I wish you would sell every component individually. Or at least the ones that are tricky to get. I would have even payed a little more to support you guys.

I will go for the 2/3 way valve from esska. I guess when it releases vacuum it takes air from the top. There is no photo of it.

Do you know if the Software needs the NC or NO option. or is solenoid polarity reversible.

Sorry for my idiot questions. Almost everything other than the metals and feeders is ordered now, I will have a photo of my beast soon enough.

[mrandt]

Hey Dave,

here is a quick drawing of the valve operation - this is the 2/3 valve normally closed:

mrandt_esska_3-2_valve.png (62.3 KiB) Viewed 10567 times

The flow of air can be inversed (in case of vacuum instead of pressure).

As a general hint: Most industrial solenoid valves look similar to this. In most machines multiple of these will be screwed into a common base plate or rail which distributes pressure (or vacuum) to the valves. So the primary input will always be that outer thread connector (bottom left in picture above) opposite of the actuator coil while primary output is usually 90°to the side. Often, the output connector can be exchanged and rotated as needed.

If you connected the needle to the side (push connector) and vacuum to the outer thread at the base, it should work fine.

I think NC is the right switching type, so vacuum will only be applied if power is turned on for the valve. But you could always invert that by using a different MOSFET to drive the valve so it does not really matter.

Cheers
Malte

P.S.: The valve from ESSKA is also not a well reknown brand, however I found the quality to be good. It costs about 30 GBP I guess. If you want a brand name and more expensive (and probably also good quality), you should check SMC or similar manufacturer. The following shop has a great selection:
http://www.pneu-store.co.uk/index.php?o ... 7&Itemid=2

[dave]

Its very hard to find -100kpa rated valves so I will take your advise and let you know how I get on.

If anyone knows of SMC part let me know. I am tried of looking.

[mrandt]

Its very hard to find -100kpa rated valves

-100kpa??? That would almost equal total vacuum at sea level... Without *really* expensive equipment, you will never produce that kind of negative pressure

Also, you don't have to. I run my machine with about -60kPa and that is already more than necessary. Not sure how much suction the pump from Juha's kit produces.

[dave]

Hi

I mean any -kpa really. Nearly everything this is rated for + pressure.

I will just chuck it all together and hope for the best

[WayOutWest]

I think NC is the right switching type, so vacuum will only be applied if power is turned on for the valve.

My experience too.

I spent a bit of time thinking about this. Assuming the pump is on, the system is under the least stress when the solenoid has no current passing through it and the pickup head is not picking-up (i.e. vacuum is pulling air through the open port of the solenoid, not the tiny needle).

If you use high quality solenoids and pumps this probably doesn't matter.

But cheap solenoids generate heat when current is passing through them, so their lifetime is basically measured in hours-with-current-passing-through-them. There's an avalanche effect towards the end where the solenoid gets hotter, which causes the insulation to degrade faster, feeds off itself... my first solenoid died this way.

So I recommend setting things up so that in the "resting state" the pump isn't fighting against the tiny needle and there's no current passing through the solenoid.

[dmwahl]

I'm getting my kit ready to assemble, and have plugged the solenoid and vacuum pump into my bench supply to make sure they work properly. I noticed that the solenoid gets pretty hot at 24V, has anyone had trouble with it overheating?

I'm putting together a quick PCB to simplify wiring of the pump and solenoid, so figured I might as well put a basic economizer circuit on it for the solenoid to keep heat down. The idea would be to initially apply the full 24V to energize the coil, then drop it down to 12V to cut the coil power by 75%. Perhaps I'm solving a problem that doesn't exist, but if the solenoid is on half the time that's a fair amount of heat (assuming equal time placing a part and going to pick up a new one). PCB will also include some diodes to clamp the flyback from the coil and pump, although again maybe not a problem.

[EDIT] I read Adam's post before mine again, and apparently yes people have problems with the solenoid heat. Should have read the whole thread better