Vacuum pump?

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Ms Wolffie
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Vacuum pump?

Post by Ms Wolffie »

So I have bought this one
Image
It says this:
With Oil Anti - flowback Design, the air passage is specially designed to prevent oil from flowing back to contaminate chamber through Electromagnetic Valve(not included)and pipeline after pump stopped.
Are they talking about a venturi valve or what is it actually?
TIA
Wolffie
Ps Guess I now need to work out how to make the plenum :P
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Wolffie

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Re: Vacuum pump?

Post by PaulRowntree »

Hi Wolffie
No, what they are referring to is an 'anti-suck-back' valve. if you empty out a chamber, then shut off the pump, the vacuum in the chamber can 'suck' the oil from the pump towards the working chamber. Not nice, for most applications. So an electric valve between the pump and the chamber that closes without power isolates the two parts. Apparently this pump's internal channels try to reduce the oil movement, but a valve is best (or just vent the chamber back up to atmosphere).
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Ms Wolffie
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Re: Vacuum pump?

Post by Ms Wolffie »

Thanks Paul.
I shall try to find one.
Is this pump overkill for my Shark?
It used to be Shark now it has been extensively modified and is called "Jaws"
SharkDiner.png
I thought that if I buy a bigger one that is absolutely necessary it could be useful if I decide to get a bigger machine.
On to researching plenums and electric valve.
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Wolffie
Cheers
Wolffie

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Re: Vacuum pump?

Post by PaulRowntree »

I haven't built a vac hold-down, so others should judge suitability; 9 cfm seems small to me, but it depends on your hold-down design : pod or plenum? I was going to try exactly your route, with a direct hose from the mechanical pump to the table, and some simple isolation valves near the work. This needs an air-tight plenum, since mdf would leak too much for these small-volume pumps. I was going to try pods made of plastic decking.

If there is no vacuum tank between the pump and the table (and the pump is going all the time that you are working) then there is no need for a valve since you are going to bleed it up to atmospheric pressure when you are done anyway. The isolation valves I have bought for my lab are expensive since they should have as large a clear bore as possible to maintain throughput, so I was not planning on buying one.
Cheers!
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Re: Vacuum pump?

Post by rscrawford »

Wolfie, that pump will not work for the typical plenum/spoilboard set-up, but it will work great for vacuum jigs.

Having a plenum with spoilboard, you need about 150-400cfm (depending on size of your spoilboard). These pumps are usually in the 12-40hp, and 3phase.

But for vacuum jigs or pods with a really good seal, that pump will be excellent. You can make a little plenum and use a gasket to seal around the edge for holding different sized flat pieces (just loop the gasket material around the grooves in the plenum for the size you need). Or you can make little jigs out of HDPE or Corian, etc. I like to create my seal around the perimeter of my workpiece with 1/8" thick closed cell weather stripping. I cut a groove .08" deep, and stick the weather seal down in that groove. It sits slightly proud (about .045"). When you turn the vacuum on your workpiece will compress the foam and sit flush against the jig. You should be able to pull 25"hg with that pump and a good seal on your vacuum jig.
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Re: Vacuum pump?

Post by fretsman68 »

rscrawford wrote:Wolfie, that pump will not work for the typical plenum/spoilboard set-up, but it will work great for vacuum jigs.

Having a plenum with spoilboard, you need about 150-400cfm (depending on size of your spoilboard). These pumps are usually in the 12-40hp, and 3phase.

But for vacuum jigs or pods with a really good seal, that pump will be excellent. You can make a little plenum and use a gasket to seal around the edge for holding different sized flat pieces (just loop the gasket material around the grooves in the plenum for the size you need). Or you can make little jigs out of HDPE or Corian, etc. I like to create my seal around the perimeter of my workpiece with 1/8" thick closed cell weather stripping. I cut a groove .08" deep, and stick the weather seal down in that groove. It sits slightly proud (about .045"). When you turn the vacuum on your workpiece will compress the foam and sit flush against the jig. You should be able to pull 25"hg with that pump and a good seal on your vacuum jig.
Russell, thanks for sharing your info, can you point to a link that shows the actual close cell weatherstripping that you use?

Thanks again,
Dave
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Re: Vacuum pump?

Post by Leo »

Wolfie - THANK YOU greatly for this tread.

I will be following your progress on this with great interest.

Even is the pump is small and can only work for a jig - WOW - this will be a great learning experience.
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Re: Vacuum pump?

Post by rscrawford »

fretsman68 wrote:
Russell, thanks for sharing your info, can you point to a link that shows the actual close cell weatherstripping that you use?

Thanks again,
Dave
Here is what I use.
http://www.homedepot.ca/product/closed- ... ape/947895 Cheap and easy to find. I bought some expensive vacuum gasket material and this stuff is pretty much the same. Be sure its closed cell foam, and 1/8" thick seems to work the best (but you need to set it into a groove, so your workpiece will be able compress it and sit flat against the jig).

Here is an example of a jig I've posted before for cutting chair seats. The foam gasket sits inside the vacuum pocket, and creates a good enough seal that my venturi vacuum source will pull 25"hg. These jigs are a little more complex, because they index onto my aluminum vacuum plenum and have removable indexing blocks for 2 sided cutting of the seat joints, but you get the picture. That pump Wolffie bought would be perfect for my jig system. My venturi works fine, but uses a lot of air.
chair seat 1.JPG
chair seat 4.JPG
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Re: Vacuum pump?

Post by fretsman68 »

Thank you sir!

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Re: Vacuum pump?

Post by spinningwood »

The vacuum pump pictured looks like an A/C type pump that is generally intended to be used outdoors. It will likely emit a lot of oil mist while working. Something you might want to check before spending a lot of time on jig building.

Ed

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Re: Vacuum pump?

Post by Norb »

Wolffie

If you can't find that weather stripping tape rscrawford suggests, you might check your hardware stores for mosquito screen spline. I would get 6mm dia if you can but 5mm will do the job too......something like this http://www.bunnings.com.au/products_pro ... spx?page=3
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Re: Vacuum pump?

Post by Greolt »

This is an old thread but the first couple of posts show the plenum I have been using for years. (and others similar)

Use 1/4" round closed cell sponge rubber as gasket. Cheap and easy to get.

I have one of those vacuum pumps. Works great but puts out an oil mist which must be dealt with.

http://www.cnczone.com/forums/cnc_wood_ ... mping.html

Greolt

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Re: Vacuum pump?

Post by Ms Wolffie »

spinningwood wrote:The vacuum pump pictured looks like an A/C type pump that is generally intended to be used outdoors. It will likely emit a lot of oil mist while working. Something you might want to check before spending a lot of time on jig building.

Ed
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Wolffie
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Ms Wolffie
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Re: Vacuum pump?

Post by Ms Wolffie »

Leo wrote:Wolfie - THANK YOU greatly for this tread.

I will be following your progress on this with great interest.

Even is the pump is small and can only work for a jig - WOW - this will be a great learning experience.
I sure hope so and the price was right as well
Cheers
Wolffie
Cheers
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Ms Wolffie
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Re: Vacuum pump?

Post by Ms Wolffie »

Norb wrote:Wolffie

If you can't find that weather stripping tape rscrawford suggests, you might check your hardware stores for mosquito screen spline. I would get 6mm dia if you can but 5mm will do the job too......something like this http://www.bunnings.com.au/products_pro ... spx?page=3
Thank you Norb.
We are going to Cairns on Wednesday, I will try Bunnies and Masters.
Cheers
Wolffie
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