Vacuum switch dilema...

General Composites Discussions Composites Talk
#1

A friend of mine is slowly thinking about getting into composite infusion and asked me a question that I wasn’t exactly sure of the correct answer to give him… I am hoping you guys can help me out with this…

He is currently keeping his vacuum pumps on throughout his entire cure cycles, but wants to start using a vacuum pressure switch so they turn off at full Vac and kick the pumps on at pressure loss.

His problems…
Problem 1 is that the torque of the pumps won’t spin the pump back on if the Vac is more than 15hg. So in his set up the vacuum pressure would have to drop significantly before the pumps would kick on again.

Problem 2 is that the switch he is looking at getting would switch back on at a pressure loss of 4hg, so the pumps would be sitting there with power going to them until the pressure dropped enough for the to be able to spin again.

I told him to ebay his pumps and get one that will be able to kick back on regardless of the current pressure and to run the switch that he wants… but I don’t think he is too keen on having to sell his current pumps.

What are your thoughts?

-C

#2

Take a look at this site for Ideas onn your problems
http://joewoodworker.com/veneering/EVS/concept.htm

#3

Ditch the pumps.

although it is perfectly possible to use these pumps, you need some extra plumbing (non return valve, bleed valve) which operate electrically, which turn up the cost such that it makes more sense to buy another pump.

As for the switch: if the hysteresis is 4 Hg, then this is way too much as well. I bought one of the ultra cheap switches of Joe Woodworker, out of curiosity, but it is totally useless for composites.

Either get a good quality mechanical switch (Danfoss RT 121) or an electronical one (SMC, one is advertised on this forum) which needs at least a power supply and a relais (preferably solid state, but electro-mechanical can do the job as well)
I rig the RT121 with a relais as well, by the way. Mostly because I use them with 3 phase pumps.

#4

Dshowalt,

Thank you for the link… that is a good read and a pretty cool idea. I forwarded the link onto my friend, I’m sure I’ll hear back from him within the week.

Herman,
My thoughts exactly. The best answer I could give him when he first approached me about it all was that he should just get a new pump. I didn’t consider however that the 4Hg was too large of a dwell span.

I know he isn’t doing anything production, but little hobby bits and pieces… I think he was just concerned about leaving his pump running through the entire length of the cure.

I’ll pass on your answer to him as well and allow him to bounce thoughts off me as he considers his options.

Thanks guys for your input, it is always valued!

-C

#5

Hi Herman
Can you please tell a little more about this danfoss Rt 121
I’m looking to choose a switch and this one look like an easy to use and to connect
Can you tell the right way to connect this to an Edwards E2M8 pump
And to connect the relay for it
Also does it need a damper?
The pump is rated 10amps during working and 30 at startup I think
It a 110 volt USA
Maybe you have an instruction manual …I look all around the web but couldn’t find
Thank you Phdledge

#6

Professional or hobby. It does not matter. If you want a good result, use good tools.

It is hard to get a good result using good tools
It is even harder to get a good result using bad tools

Do you think Michelangelo only used a hammer and chisel to make his sculptures? No way, I am sure this guy just had a 5 axis CNC router, just like all professionals… :slight_smile:

I will look for the schedule to connect an RT121 to a pump, using a relais. It is really simple: The RT121 is a purely mechanical switch. Connect 1 phase to the RT121, and the other side to the A1 of the relais. A2 goes to neutral. This should allow the switch to operate the relais. The L1 to L3 of the relais can be used to connect the pump.

#7

Herman,

I love your little joke comments you add into some of your posts, it keeps everything very entertaining!

-C

#8

Is this http://www.idealvac.com/files/ManualsII/Edwards_E2M2_to_E2M12_Users_Instruction_Manual.pdf what you’re looking for ?

#9

Thank you but I have the pump manual
It was nice from you but what I’m looking for is how to connect the vacuum switch and relay If needed to the pump
No company who make this switches have an install graphic to show how to connect it for the composites application

#10

I somewhere have a scan of what my father once put on paper. If I cannot find it I will try something in paint or so. (am not a graphic artist, so beware…)

Will be late, however.

#11

A vaccum advance unit with a micro switch attached to it is what I use. I have a spring rigged to the vaccum advance to make it adjustable so I can set it from 29- 20 inHG