Author Topic: Vacuum pump  (Read 8228 times)

Offline Brass_Machine

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Vacuum pump
« on: May 26, 2008, 12:39:48 AM »
I am considering building a vacuum pump system to do some vacuum bagging for some composite work. I have been thinking about this Guys plans. I already have most of the stuff in his plans including a decent vacuum pump. Just need to get off my @ss and do it. He has some decent plans... check them out.


Eric
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Offline PTsideshow

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Re: Vacuum pump
« Reply #1 on: May 26, 2008, 06:32:00 AM »
They are very clean in design and build. ;D
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Offline Rog02

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Re: Vacuum pump
« Reply #2 on: May 28, 2008, 06:18:18 PM »
I am considering building a vacuum pump system to do some vacuum bagging for some composite work. I have been thinking about this Guys plans. I already have most of the stuff in his plans including a decent vacuum pump. Just need to get off my @ss and do it. He has some decent plans... check them out.
Eric

Hi Eric:

Those are some pretty nice looking vacuum set-ups for laminating veneers.  There really is no need for a reservoir for bagging composites however.  I have bagged my fair share of pre-preg at the helicopter company and never needed a vacuum reservoir for anything except the vacuum forming table.  A properly constructed reservoir will increase the volume of air that can be displaced in a hurry which may be nice when vacuum clamping furniture pieces, but may be too quick for composite work.  It is usually desirable to evacuate the bag slowly as it allows for last minute adjustments and prevents wrinkling which can in turn leave uneven resin dispersion in the matrix.  A properly constructed bag will have little volume to evacuate.

Should you decide to build the reservoir, remember vacuum can create some high crushing pressures.  We used to crush five gallon thinner cans by hooking them up to the shop vacuum supply.  I have however constructed resin traps from heavy pvc fittings and they have performed well.

A word of caution on vacuum pumps is in order as well.  Many people are using old AC service vacuum pumps for small projects.  Be advised that most of those pumps are "oil pumps" and can introduce oil into the bag once the seal has been established and the atmosphere has equalized. 

For some basic "How-To" on getting started with composites look at the Fibre-Glast Learning Center.  http://www.fibreglast.com/contentpages-main-Learning-Center-283.html

West Systems Epoxy also has some good information and articles available on their website.http://www.westsystem.com/

http://www.bertram31.com/proj/tips/vaccuum.htm Is a brief primer on the process and shows both the full sleeve bag and the surface seal bagging method.
Roger
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Offline Brass_Machine

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Re: Vacuum pump
« Reply #3 on: May 29, 2008, 01:37:33 AM »
Thanks Rog Thats some great DVD collection from fiberglast. I do own a decent vacuum pump. It is a decent one and not an old refrigerator unit. I am just not sure how to use it in a vacuum bagging situation... like what do I need?

A vacuum gauge? A shut off valve? How do I make a resin trap?

Eric
« Last Edit: May 29, 2008, 01:39:50 AM by Brass_Machine »
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Offline Rog02

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Re: Vacuum pump
« Reply #4 on: May 29, 2008, 01:14:25 PM »
Hi Eric:

Composite structure is deceptively simple.  It may look simple, but requires some pre-planning and knowledge.  My suggestion would be to read everything you can find on the topic, invest in some basic materials and experiment some before you begin a project.

Edit;

First let me encourage you to always wear safety glasses and an appropriately rated organic breathing mask whenever handling or in the presence of composite materials.  The solvents will blind you instantly and the effects of prolonged inhalation of the fumes are catastrophic.  I also strongly urge the use of nitride gloves when ever handling resins. 

In addition to the vacuum source you will need the following;

HARDWARE:
Vacuum gauge  Available from numerous sources.  Surplus Center, Mc-Carr, etc.  Over the years I have accumulated a few gauges and frequently install more than one on larger lay-ups to insure I am getting an even distribution of vacuum.
Ball Valves  Plain old ball valves.  Available from local sources and the usual mail order suppliers.  I have had good luck with the 1/2" ball valves that Harbor Freight runs on sale.
Reinforced hose  For plumbing the bag to the vacuum source.  Use the kind with the reinforcing ply as it tends not to be sucked shut.
Sucker fitting  This is a specialty item available from any of the resin suppliers.  While there are sources on the net that advocate the use of air hose fittings for quick disconnects it is worth considering that the quick disconnect fittings for air supply are designed to specifically hold pressure.  When vacuum is applied the seals may leak as the pressure differential is 180 degrees out of design parameters.
Scales  Used to measure resin and catalyst for mixing.

Bagging Supplies: (Mostly expendable items and may not be re-used)
Peel Ply  This is a release layer placed over the matrix before subsequent layers to eliminate the bonding of the bagging materials to the structure.  Peel Ply also promotes a smoother finish in the finished structure.  The type of peel Ply used will be dictated by resin type used.
Breather Cloth  A polyester blanket of non woven material that allows the air to flow out of the bag evenly.
Bag Tape  For sealing the bag and plugging holes and tears.
Bagging Material The actual membrane material used to construct the atmospheric barrier.  Again your choice of resins will dictate the bag material type used.

Resin and Catalyst  OK this is up to you and will be determined by many factors such as type of structure, temperature in the shop, ultra violet exposure, end use temperature, and many other factors.  Best advice is to read the suppliers material and ask questions.  Do Not! mix suppliers.  Resins and catalyst are formulated to work together and less than desirable results may occur should products from different suppliers are intermingled.
Reinforcement Material  E-glass, Bi weave, Roving, Mat, Kevlar, Carbon fiber?  This is another choice that will be dictated by the engineering of the part. 
Fillers  Micro-Balloons, Cabasil, Talcs, etc.  These are materials often added to the resin mix to thicken it.  Useful when building up fillets, etc.

This just the short list of materials and hardware.  Also to be considered, shop environment, ventilation, and Personal safety equipment.  There have been text books written on this topic and I personally endured a 4 credit hour course on Non Metallic Structure while working on my Engineering degree. 

The schematics shown at http://www.bertram31.com/proj/tips/vaccuum.htm will give a good overview of the basic process.
« Last Edit: May 29, 2008, 04:56:37 PM by Rog02 »
Roger
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Offline Brass_Machine

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Re: Vacuum pump
« Reply #5 on: May 29, 2008, 03:37:55 PM »
Hey Rog,

I have done some composite work before, both CF and glassfiber. I have made molds etc.. But I have never done vacuum bagging though. I own a bunch of books and videos  on the subject. I just haven't attempted it yet.

Thats a great link, thanks!
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Offline SPiN Racing

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Re: Vacuum pump
« Reply #6 on: January 07, 2009, 10:37:50 PM »
Hi all,

I work at a race shop that makes small Formula 500 cars. A Class of small foruma cars powered by a small Roatax snowmobile engine, with a CVT from a snowmobile. I could go on and on about the performance but thats not the point. :)

We make a variety of composite parts, as well as very light bodywork. A lot of parts we make are "bagged"

The owner of the shop has made a very very nice.. and simple design that was incredibly cheap.

CHEAP being the prime word to hear there.

He used a vacuum pump from a old Freezer AC system. (Used appliance place anyone?)
Then he used 6 old FREON metal containers.. that look a little smaller than a standard Propane tank.
Each of these is connected together with a simple wooden frame.. and the outlets are connected with some PVC plumbing from the sprinkler department.
He has a ball valve that leads to the tanks.
THe ball valve leads to a manifold he made with a DOZEN ball valves leading to small 1/4" clearish plastic water lines.. like those used in refrigerator water feeds.
ONE valve leads to the vacuum pump.

He simply closes everything BUT the vacuum pump valve.. and the tanks.
Runs the vacuum pump while he sets up the run of parts he is gonna make.

The parts are laid out in thier spots on a big sheet of glass he got cheap at a window place. (It was cut huge.. but incorrectly)
He lays out the cotton like bleeder cloth, and then lays a VERY small 1/8 or smaller snake of clay around the outline of the part he is laying up.
Once the vacuum pump is done, he mixes up the resin.

We LIGHTLY goo the parts.. in this case they are all flat parts for chassis reinforcement.. but they could be on a mold.. simply put the clay around the preimeter.
Lay the lightly resined parts up.. be they carbon, kevlar, or simple glass.
Lay a bleeder cloth over the part (cut slightly oversize to the shape)
Lay the peel ply (Clear plastic) over the part, and tuck a hose end fromt eh vacuum manifold under it with a snall snake of clay around the hose.
Finger along the clay lightly.. and move to the next part.

After 20 or 30 minutes they are all layed out.

Flip of each of the ball valves that are hooked up, and then SLURPPPP.. he throws the main valve.

Instantly the whole thing sucks down real good.. and the bleeder cloth picks up the spare resin from the parts.
He then throws on the vacuum pump again and lets it slowly chug for the next half hour or so while the resin kicks off.
SPiN Racing

Offline PTsideshow

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Re: Vacuum pump
« Reply #7 on: January 22, 2009, 11:57:09 AM »
In the latest HF flyer they have two new real style vacuum pumps for fridge systems. a 1.2cfm $69.99 98074http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=98074
And a 2.5CFM $89.99 98076 http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=98076
Could be a low cost pump for the occasional user.
 :thumbup:
"The internet just a figment, of my imagination!' 
 
 There are only 3 things I can't do!"
Raise the Dead!
        Walk on water!
                 Fix a broken heart!
and I'm working on the first two!
glen