What size vacuum pump?

General Composites Discussions Products Talk
#1

I’m looking at a Robinair 6cfm or 10 cfm vacuum pump. Both pull to 20 microns, but I’m wondering if I should invest in the pump with more cfm. All of my molds are 6"x12" or smaller and I wanted to run 5 at a time- possibly more in the future.

Is 4 cfm really that big of a difference when you are pulling vacuum on more than a couple of molds? Will the 10 cfm pump simply pull the air out of the bag faster, but in turn pull the same amount of vacuum because it is still rated at 20 microns?

Any help would be greatly appreciated.

Thanks!!

#2

You are correct, the higher CFM means it pulls air out faster but they all reach the same ultimate vacuum. What you should do is hook the pump up to a resevour and tap lines into that instead. Have a kill switch to turn the pump on at anything below 27" and turn it off at 30" The best way to build the resevour is by using 4" thick PVC pipes. If your parts are small like you have described then you should be fine. You can always add another pump to the cluster once your need increases.

#3

I was going to run a larger peice of PVC to a reducer, into 1" PVC, with 5 valves installed along my workbench. I’m interested as to how the resevoir type system will be more eficient.

I’ve got a couple of questions and I already really appreciate the assistance.

How big should the resevoir be? Could you supply a quick diagram of how the whole system should look?

What kind of guage would measure vacuum? Where would this guage go (on the resevoir?) and do you have the guage available for sale?

What kind of kill switch would coincide with the “vacuum guage” to turn the pump on and off?

Right now I’m using my air compressor with the vacuum attachment tool. In another forum you mentioned a device that would lock the vacuum in the bag and you could actually disconnect the air line. Where can I find this product? Simply an on/off valve?

Thank you so much for your help,
Danny

#4

I’ll see if I can draw up a diagram for you with photoshop. Been so busy.

#5

Thanks Evan!!

Oh, and I’m looking forward to getting my first order from you. Kinda tired of spraying release agent before each process!!!

Also, gonna try the clear gel coat. I’ve been using clear automotive paint.

-Danny

#6

Ok here’s a basic diagram. You can set yours up however you want I guess.

If you’re not doing infusion then you can just ignore the pressure pots.

#7

I set my system up similar to that but I am doing infusion and I have never used a pressure pot. What is this used for and where can I get them?

I’m still looking for a vacuum switch and gauge that will turn the pump on and off to maintain a set vacuum. Any ideas?

Thanks again!!

Danny

#8

Oh, and I’m also still looking for the quick disconnect type system that you were talking about in another forum. I have brass ball type valves on each line, but they do seep the vacuum when I close them.

Thanks!!

#9

I can order the quick disconnects for you. They’re about $20 for the set of couplings. The pressure pot is primarily used to catch excess resin. So the resin will run into the pot instead of into the resevour and even your pump. Resin + pump = broken pump :frowning:

Pressure pots can be had for very little if you look hard enough. I don’t sell them YET because I haven’t found any decent deal on them.

#10

For the switch, try a place in Anaheim, CA called AVAC. I’ll get you more info on them tomorrow when I get back to the shop.

Evan

#11

Evan – do you think this would work for infusion?

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=37515

Jim

#12

Jim,

It might not work. You want the ports to be separated and not all together like that. You’ll 4 separate ports

  1. inlet - to pump
  2. outet - to layup
  3. vacuum gauge
  4. bleed off valve
#13

i use that pressure pot and works fine for me. I have found better ones before but it does work

#14

Thanks EMI – I looked at the exploded diagram and figured that I could take all the fittings off and modify it easily with a dremel to get what I need.

My other thought was simply to use some pvc and throw it out after each use. Since I’ll be using pretty small volumes of fiber and resin, this might actually be the more economical way to go.

Jim

#15

word of wisdom, make sure to wax the pressure pot