Building a vacuum table.

[satdaveuk]

Another place a good compressor can be found is the old industrial freezers, I built my first garage compressor with one of those together with a car gas conversion tank for the reservoir which you would also need to implement.
I mounted the whole thing Incl motor drive on the old bottom half of a super market shopping trolley and welded a metal plinth to it.
The pot size on some of those compressors from the old freezers are around 50cc bore so connecting one of those into a reservoir which a medium/large camper gas cylinder would do nicely for what you need together with a Gauge and PSI Limiter valve to switch motor off when required pressure is in the tank.
All I ever bought for that project was a good quality spray gun and Gauge the rest was from scrap
It will work and if I can spray a car with two charges which takes 20mins per charge, the only difference was you will be creating a vacuum so all you will need to do with those cylinder type pumps is drive in the opposite direction, which is easy because the motor is separate from pump using a pulleys and belt like on car fan belts.
The pumps themselves go on for ever so pretty sure if you get one apart from strip down and servicing which isn't rocket science, normally a degreasing and cleaning around the valve inlets/outlets plus piston cylinder head, very much like a small motor bike engine construction.
I personally think Don you should try and get away from vacuum cleaners and think more on the lines of industrial type compressors because that way you will get the optimum compression your after and allot quieter on the ears when in use.
Anyway all the best
Dave
Do a ring around Don you may be lucky, if you got to buy new it will cost a arm and a leg

[ppodg]

Hi,

Try to find:
Douglas E. Walsh: Do It Yourself - Vacuum Forming for the Hobbyist, Workshop Publishing, 1990..2005 - the best one
Vincent Gingery: Secrets Of Building - A Plastic Vacuum Forming Machine, David J. Gingery Publishing, 1999 - much worse

Have a look at the semi-automatic vacuum source valve (fig. 17 & 31) in the Walsh book.

Btw, your vacuum table is excellent - almost no dead space, but some holes seem to be blind.

[SVEN1]

Don,
Harbor Freight has a 20% off coupon in the latest sale flyer good to the 24th.

[dfbowers]

I need to take the next step in vacuum forming. Two stage! I have been contemplating this for some time now. While I can make endless variations of shells, and sometimes some nearly flawless ones, my yield is not all that great due to poor temperature control and incomplete pull downs. My goal is to make these efficiently enough to be able to help supply these to other Geotech hobbyist (Sven keeps me busy sometimes). My general idea is not original, but I am looking for details on vacuum tanks. Particularly, tank and plumbing size as well as where to find a cheap vacuum pump.

The general idea is to use a shop vac for the initial evacuation and to hold a 1/16" thick sheet of ABS to the platen and when it's still hot engage a second stage to make a complete draw. As it is, I always have a 1/4" or so near the bottom of my forms that never draws down tight to the platen. Any suggestions appreciated.

Don

Project successful! I finished my 2-Stage setup and made 11 coils yesterday for Sven (about 2 hours worth of work). The differences are dramatic over a single stage vacuum table.
I never read the book but it was pretty easy to figure out, so I will share here what I did.
I added a vacuum gauge (from Harbour Freight) just to get an idea of vacuum draw involved.

Items I used:
Vacuum table (posted elsewhere in this thread).
1 1/2 and 1/2" Schedule 40 PVC.
Three 90 degree elbows 1/2"
Ball valve with 1/2" fittings.
11 Gallon tank from Harbour Freight ($35.00). It can be connected to PVC with 1/2" NPT fittings.
Sump Pump check valve.
Craftsman 1.5 HP 2 Gallon air compressor.
Length of 1/4" rubber tubing.
One 1/4" tee with barbed fittings.
Misc 2" wood for a frame.

The general idea is to use a shopvac (through a check valve) to pull and hold a hot sheet of ABS. Then a ball valve can be opened to allow a hard draw from
the 11 Gallon airtank which has been previously evacuated. The check valve will slam shut when the ball valve is opened preventing back flow from the shop vac.

Interestingly enough, a plain old air compressor can be used to evacuate a tank simply by hooking to the input of the compressor via a 1/4" barb fitting.
My air compressor can draw a tank down to about 26" Hg in 2 minutes. In contrast, my shop vac can only pull 4" Hg!!!! Still, a shop vac can be used
for a lot of forming, provided that the ABS sheets have been heated sufficiently, but the Vacuum tank really draws the plastic into every little corner.
Don..

[Carl-NC]

Nicely done!

[Baterista]

Hello Don, excellent, very good work.

[Thomas]

Now that is slick.

[SVEN1]

That's really nice Don.
The oven problem gave me an idea. I used to do t-shirt screen printing in the 90's, small quantity orders. Because I did not need a full blown drying oven. I used a Flash Dryer. Cured the ink in about 30 seconds. Take a look at the flash dryer. You may even find a used one at a screen print shop. Might be adaptable for vac forming and other applications.
http://www.mrprint.com/en/Textile%20...20Cure%20Units

http://www.flashdryer.net/heat_element_comparison.htm

[dfbowers]

Hello, I wanted to share my latest project with everyone. Hopefully someone can use this design as well!
Don

Vacuum table plans, part II.

[Jerry]

Drat, I just threw out a tank about that size last year

I did build a clone of the table when you posted the first part. Will have to see if I can find a tank and pump.

Very clear diagrams and instructions as usual.

Thanks for posting it Don.

Jerry

[golfnut]

Unstoppable! A treat as ever

[sinclairuser]

does anyone in the uk know a supplier of these sheets?, and i'm talking at least 10 at a time(£2.50 a sheet at a craft shop).
thats for the nice thicker black stuff that don uses, i have found clear or white in model suppliers but its way too thin for our needs.
thanks ally