Vacuum pump suggestions

[Keskin]

Hi all,

i need a suitable vacuum pump to hold down 3 separate pieces of hardwood with 36x4,5 inches each. Note that each part will have it`s own vacuum fixture and will be rubber sealed so the vacuum force would be more important than the max airflow.

Cutting depth will be around 1/2 inch max, bit diameter would be between 1/2 and 1 inch max, upcut 2 flute round nose.

So what kind of a vacuum pump (specs) would you suggest for such an application?

Thanks very much for any advice.

[Geof]

For that area and type of cut you are going to need the maximum holding power possible so your pump will need to be able to pull a vacuum as close to one atmosphere as possible. A good vane pump that can get down to 28 inches of mercury will probably be the best aaproach.

[Keskin]

Thanks Geof, could you give me some specific model recommendations? I´am still pretty unfamiliar with vacuum pumps.

[Geof]

Cannot suggest any particular models.

This link shows the type I think you should be able to find over there:

http://www.welchvacuum.com/welch_vac...igh/index.html

[samu]

if you just work ocasionally with vacuum fixture and have a good compressed air supply, a venturi could be a good option, look on Mcmaster, there is good venturi pulling out a vacuum about 28" Hg for less than 80$. But it takes a lot of CFM so it's not recommended for continuous use.

[Keskin]

I`ve been doing some calculations and it seems that having well sealed fixtures is more important than the Hg pull but feel free to correct me.

Formula: Hg x square inch x 0.5 = Overall Lbs

Part1 (2"x18.5"):
24Hg Pump: 24x37x0.5= 444Lbs
28Hg Pump: 28x37x0.5= 518Lbs

It looks like there isn`t that much of a difference but then again, i have no practical experience with vacuum.

In any case, i`am still trying to figure out which "cfm/Hg" class pump would be sufficient for my purposes, i don`t want to pay too much for a pump that would practically be overkill for me.
Just for some clarification, i`ll be cutting parts exclusively held by sealed and custom shaped fixtures, so no leaks during the whole process.
And the pump has to be able to endure daily usage.

I figured that 26Hg or more would be fine but what minimum "cfm" would be necessary to hold down 3 parts simulaneousely with 37 square inches each?
Since i`ll be cutting wood and the fixtures wont be a 100% airtight, the pump has to have a sufficient "cfm" to compensate.

Thanks again, any help is appreciated.

[samu]

I never test it but I know that you can achieve good result with a old fridge compressor. But dont't forget that wood is a porous material that let pass some air. Especialy if it is mdf.

[John J MURPHY]

Remember that if f you cut a channel for the rubber vacum seal, so the seal will recess and the part will be flush against the holding fixture, i.e., "spoilboard" you will then have to increase the "vacuum surface area" of the parts being held beyond that of the vacuum holes themselves.

If you peel and stick a thin and narrow gasket to the surface of your fixture you will have the max "VSA" and only have to adjust the Z axis (if even necessary).

Good Cutting!

John Murphy
www.allstaradhesives.com

[Keskin]

Thanks for the tips guys.
Thanks to the forum I learned a lot about vacuum so I won`t have to do a lot of experimenting.