Use the force Luke....

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ultramegabob

ultramegabob

Senior Member
Location
Indiana
I went on an interesting service call today where the customer is running a small business making Storm Trooper suits for high end Star Wars fans, a customer was having problems with thier vacuum forming machine tripping a breaker, I got the issue taken care of for them easy enough, but then they mentioned in passing how it was hard to work all the valves on their contraption to keep the plastic hot and not set up before all the air is sucked out. I figgure I could install some solinoid valves and make them a control panel with switches and or relays for however they want it to work, but when I priced the solinoid valves at the supply house they were 200 bucks apiece, kind of out of thier budget, I was hoping to find some suggestions for less expensive solinoid valves, I thought about using zone valves for lawn sprinklers, but I dont know if they would allow enough flow or even hold vaccum.... any input is appreciated.
 
TOOL_5150

TOOL_5150

Senior Member
Location
bay area, ca
Sprinkler valves wouldnt work using a vacuum. They work under pressure, using the pressure to push on the diaphram to close the valve.

~Matt
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Have you checked Grainger? They're not always cheap, but they have just about everything.

I can ask the fire-suppression guys I work with how much the electric gas valves cost.
 
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hardworkingstiff

Senior Member
Location
Wilmington, NC
ultramegabob said:
...but then they mentioned in passing how it was hard to work all the valves on their contraption to keep the plastic hot and not set up before all the air is sucked out. I figgure I could install some solinoid valves and make them a control panel with switches and or relays for however they want it to work, but when I priced the solinoid valves at the supply house they were 200 bucks apiece, kind of out of thier budget, I was hoping to find some suggestions for less expensive solinoid valves, I thought about using zone valves for lawn sprinklers, but I dont know if they would allow enough flow or even hold vaccum.... any input is appreciated.
Click to expand...

From your pictures, it appears only 2 valves really need to be controlled. If the plastic is cooling before the vacuum pulls it into place (I understand that is the problem) I would have to wonder if the problem is actually the vacuum pump may be undersized, the ball valves are reduced port (instead of full port), or the hose may be too small. There may also be very small vacuum leaks in the piping/hose assembly that may cause a longer duration for the pull down at the mold.

You might also check to see if there is too much voltage drop to the vacuum pump causing it to perform less work.

This looks like a home made rig and your involvement will probably become altruistic. Nothing wrong with that, just know that's where it's probably going.

As far as solenoid valves, Grainger has some general-purpose units that are less than what you were quoted.

Good luck, please let us know if you get involved and how it turns out.

Edit: If the pump stays running, get the valves as close to the mold as possible, that way the vacuum in the system is already pulled and the vacuum acting on the mold will be faster than if the valve is farther away and the vacuum has to work its way through the hose. Another thing that might help is if a tank is put in place between the pump and the control valves to store vacuum. Sort of like putting a pressure regulating tank on a well pump. This will help a lot if the vacuum pump is marginally sized for the work.
 
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hardworkingstiff

Senior Member
Location
Wilmington, NC
iwire said:
No it would not work.


The incoming pressue seals the valve.
Click to expand...

If vacuum is on the discharge side of a valve, then you have pressure differential on the valve with the inlet side being higher than the outlet side thereby acting just like you installed pressure on the inlet side.

Why won't this work? The pressure on the inlet side (created by the vacuum on the discharge side) would seal the valve.

I have installed solenoid valves on gas/diesel system lines that feed suction pumps (inlet side to the tank and discharge side to the suction pump) and if the valve is not energized, the pump will not pull through the valve.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
hardworkingstiff said:
If vacuum is on the discharge side of a valve, then you have pressure differential on the valve with the inlet side being higher than the outlet side thereby acting just like you installed pressure on the inlet side.
Click to expand...

I agree

Why won't this work? The pressure on the inlet side (created by the vacuum on the discharge side) would seal the valve.
Click to expand...

Maybe it would but I really don't think so. I seriously doubt the pilot passages and pilot valve would operate the diagram in this way.

Unless it is for my own use I prefer to use valves as the manufacturer intended.:smile:
 
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hardworkingstiff

Senior Member
Location
Wilmington, NC
iwire said:
Unless it is for my own use I prefer to use valves as the manufacturer intended.:smile:
Click to expand...

I believe it is. The valves are designed to block flow from a higher pressure to a lower pressure. The valve has no idea if the pressure differential is caused by introducing pressure on the inlet side or vacuum on the discharge side. Same same as far as the valve is concerned.:smile:
 
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