Vac-Forming Machine Vac Options??

monoman527911

monoman527911

New Member
First off let me say hello! Iv been here a while but this is my first post on the RPF so here we go!
Ok so after many months of work and research my Vacuum table is all ready to start pulling :)
but...

All I have got to make the vacuum is a 3.5 hp shop vac and I'm concerned at the amount of detail I'm guna be able to get with it..

I still haven't really got a grasp on the option of getting a vac pump and tank set up so can anyone help me out with where to start with that or throw some more options out there?

appreciate it :thumbsup


-Steve
 
Been pulling for 9 years on home built systems and in my experience I've found:

The shop vac (8" mercury on a good day) will pull plastic (up to .060") with decent detail.
A Dental Vac (14" mercury) will pull (up to .125) with good detail.
A High Vac Pump (22-29" mercury) will pull with excellent detail and crush a mold that isn't built right.

The tank is for building up volume of negative pressure and should be at least equal in volume as the volume size of the table (figure height as that of your tallest mold). For High Vac Pumps, narrow your options by first determining how much pressure (" mercury) you want. Then choose it's cubic feet/minute rate by how fast you need it to recover between cycles (1/4 hp and a 2 hp pump pulling 26" mercury will do the same thing, but the 2 hp will do it faster)

I run a 1/2 hp Gast pump (110v) on a 30 gallon tank to draw down a 24"x 48" table at 23" mercury with a cycle time of 3 min. on ABS .090". It's also worth noting that the pump alone is able to draw down the plastic, but at a much slower rate. The tank gives you INSTANT vacuum and allows for a more even stretch of material across the mold.

hope this helps,
-K
 
Superkrates said:
Been pulling for 9 years on home built systems and in my experience I've found:

The shop vac (8" mercury on a good day) will pull plastic (up to .060") with decent detail.
A Dental Vac (14" mercury) will pull (up to .125) with good detail.
A High Vac Pump (22-29" mercury) will pull with excellent detail and crush a mold that isn't built right.

The tank is for building up volume of negative pressure and should be at least equal in volume as the volume size of the table (figure height as that of your tallest mold). For High Vac Pumps, narrow your options by first determining how much pressure (" mercury) you want. Then choose it's cubic feet/minute rate by how fast you need it to recover between cycles (1/4 hp and a 2 hp pump pulling 26" mercury will do the same thing, but the 2 hp will do it faster)

I run a 1/2 hp Gast pump (110v) on a 30 gallon tank to draw down a 24"x 48" table at 23" mercury with a cycle time of 3 min. on ABS .090". It's also worth noting that the pump alone is able to draw down the plastic, but at a much slower rate. The tank gives you INSTANT vacuum and allows for a more even stretch of material across the mold.

hope this helps,
-K
Click to expand...

wow ..i love it when they talk techy....I need a cigarette.
 
Thanks for all the info!
It seems like all the vacuums i find do not show the mercury number..
not sure why..
Id like to find a middle point between the shop vac and like a 700 dollars and up pump kind of thing

any suggested models?


-Steve
 
I've used both a 3.5 and a 5 hp shop vac for years and years, and never had a problem. I don't expect super detail in vacuforming... I'd pull stormtrooper parts or a proton pack base with either, and get great results. I use the 3.5 for about 90 percent of the time, using the 5 hp for really thick plastic. And I got both vacs at Sears.
 
Just ran a search on ebay with the search parameter of 'Gast Vacuum Pump' and found MODEL#72R634-P130-D303X. It pulls 25hg with 1/3 hp 115v motor and has a buy it now for $55.00 (US). couple that with a portable air pressure tank from Home Depot and you're in business.
 
AWW! Great find!
Thanks so much for the help guys..I'm guna go head and order it asap
Ill snap some pictures and post them soon as i can to show what I'm working with..
So let me make sure iv got this figured out:
-connect the vac pump to the tank
-have a pipe going up to a valve and connecting to the forming table
sound about right?


-Steve
 
monoman527911 said:
...-connect the vac pump to the tank
-have a pipe going up to a valve and connecting to the forming table
sound about right?


-Steve
Click to expand...

Yes, and unless your pump has a backflow check-valve, you may want to place a valve between the pump & tank - this will allow the tank to hold pressure when the pump is not running.
 
I've just finished building my machine and have a ton of pics up, including the plumbing:

http://www.flickr.com/photos/tk7602/sets/72157623135056391/

This pic is a bit outdated... I've flipped around the vacuum gauge and valve, so that the gauge isn't on the OUTSIDE of the system. That was an "oops" on my part:



I don't think you'll find inches on any sort of home/shop vac, since that's not the sort of thing people tend to care about.

I picked up a Gast 0823 from Craigslist for $100. It pulls 20 gallons down to 26" in about a minute, so I'm happy.
 
really cool set up ya got there man..
Any reason you are using two tanks as opposed to one larger one?

What are you guys using for your heating unit?

Iv built the design tk560 has up on his site with the Nichrome wire coils and cement board oven..I'm still working out the kinks tho..its tough getting it to heat evenly
but overall it should do just fine i think
 
monoman527911 said:
Thanks for all the info!
It seems like all the vacuums i find do not show the mercury number..
not sure why..
Id like to find a middle point between the shop vac and like a 700 dollars and up pump kind of thing

any suggested models?


-Steve
Click to expand...

Once you see a vacuum gauge working and test suction on different materials, you get a better understanding about the difference between a vacuum pump and vacuum cleaner.
Full vacuum is 29.5"Hg. Most vacuum forming only ever needs 20 - 25"Hg.

Vacuum cleaners including shop vacs may be able to evacuate the air quicker, but they max out their suction at about 6"Hg. This is where a surge vacuum pump connected to a tank comes in. You can take a surge tank right up to full vacuum and store it, ready for the pull and the pump is turned on to charge that again.

Something I found by experimentation is that MDF (a material commonly used in home made vacuum formers) is really only good for 6"Hg. After that, the pump pulls air through the material. So you need laminated materials, plastics or even metal to reach high levels of suction to get better details.

My first vacuum pump was a single stage 3cfm unit that I bought new off eBay for $103.
My current pump is a 2 stage 9cfm pump and I paid $217 for that. At retail, this pump is $1100 and the guy selling on eBay had 20 of them listed at $1100 each. Everytime he sold one, the price of the remaining pumps dropped. There was 2 left when I bought mine and now I wish I had bought both.

Good vacuum cleaners cost more than what I paid in total for my pumps.
 
Last edited:
Hi, I am a newbie at vacuum forming so I was just wondering why do you have to use air tanks that are attached to the air pump?
 
yoman503 said:
Hi, I am a newbie at vacuum forming so I was just wondering why do you have to use air tanks that are attached to the air pump?
Click to expand...

They are storing a vacuum in reserve. So you pull suction and when you open the valve, you have instant max suction that is almost 4x that of any vacuum cleaner and that rush is fast.
 
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