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Best way to plumb a platten (to the tanks and vac)?

 
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knightshade
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Joined: 19 Jun 2005
Posts: 123
Location: Rochester NY

PostPosted: Sun Feb 27, 2011 10:13 am    Post subject: Best way to plumb a platten (to the tanks and vac)? Reply with quote

Starting to plan what I want to do for my vac table when I get to upgrading it this summer.


I've been looking over the proto-form plans, and will be going down a similar path - but I'm looking to use my existing tanks/pump.

The pump is a Gast 1023, and I've got two old hot water tanks (30 and 40 gallon).

With my first table (functional for pulling ABS), I used 1/2 inch pipe, as well as some hefty hoses to connect the tank (4' in length).

Well - after watching some Mythbusters episodes about air cannons, I've come to realize that wider pipes, and shorter distances would likely help with vac forming too. (Who said that TV can't be educational?)
(The quicker the air is evacuated, the more detail that should transfer)


So - that brings me to thinking:
What is the best way to move forward?

I'm leaning toward plumbing it with two master valves.

Forgive the ascii art:

Code:

            Platten
   ===============
            ||
            0 Dump Valve
            ||
            | =======  Vac Pump
            ||
            0 Tank Shutoff Valve
            ||
            ||
            ||
           Tank(s)




For Operation:
- Close dump valve, Open Tank Valve - turn on pump
- Heat & lower plastic
- Pull the dump valve
- After Equalization - close the tank valve
(and let the pump do it's thing with the minimum possible volume)


the open questions are:
How much does distance play a part? (additional volume being obvious)
What width piping are folks using?
(Limiting factors: 1/2" connector on the pump, multiple 3/4" connectors on the tanks)

Assuming that I build an aluminum platen -
What connector us used (glued/siliconed PVC seems to be common)...
Will that attach to other pipe (such as black iron?)
Or would all of the plumbing be PVC?
(Any drawbacks to using PVC for vac plumbing?)

For the main dump valve - what is the largest size that is going to be reasonable to find/use? (1" inner diameter? Bigger?)

Thanks for any input?
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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Mon Feb 28, 2011 8:40 am    Post subject: Reply with quote

Seems like a lot of our vac formers are in a constant state of upgrade as we do bigger & better things!

A couple questions to start determining what you want to do.

What size is your vac former?

How large is the biggest mold you plan on using? In other words, how much air needs evacuated. You may not need the two stage system if you've got 70 gallons of vacuum. My tank is only 30 gllns on a 2'x4' sytem. On a large pull that's around 6" near vertical (lots of trapped air space) I seldom if ever need the two stage.

Concerning the platen, are you doing mostly one-off type pulls or production forming? If you're doing production consider mounting the mold/s to the platen to make release of the formed ABS faster & simple. That will dictate what type of platen you make and if it is as complex as the Proto-Form. The Proto-Form is excellent for prototype work but that's a lot different than production forming.

hth, DougN
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knightshade
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Joined: 19 Jun 2005
Posts: 123
Location: Rochester NY

PostPosted: Mon Feb 28, 2011 4:21 pm    Post subject: Reply with quote

jdougn wrote:
Seems like a lot of our vac formers are in a constant state of upgrade as we do bigger & better things!

Mine has been on hold for a while.
Last year I built a armor building workshop (12'x16' shed) so that I had a place for vacforming. LOL - the kids and wife don't like the noise levels of the pump running.

jdougn wrote:

A couple questions to start determining what you want to do.

What size is your vac former?


Currently 2'x2' - pretty closely followed tk560's plans a few years back.

When I rebuild, I'll likely build a larger machine - but stick with a 2'x2' platen & plastic frame for now. (All of my plastic stock is 24" squares)

jdougn wrote:

How large is the biggest mold you plan on using? In other words, how much air needs evacuated. You may not need the two stage system if you've got 70 gallons of vacuum. My tank is only 30 gllns on a 2'x4' sytem. On a large pull that's around 6" near vertical (lots of trapped air space) I seldom if ever need the two stage.


Mostly pulling armor parts for costuming...
chest armor or a Navy Talker helmet are some of the larger molds.
(That helmet is probably 10" tall.)

Long story short - my current table has a platten that leaks.
It was MDF... initially unsealed (worked for HIPS).
I sealed it - but it still has a small leak somewhere.
The second tank fell into my lap, and the added vac was very helpful when I tried to pull ABS.

I'm doubtful that I'll need the two stage - I don't use it today, and I'm not unhappy with the detail that I can pull. Most of my complaints with my current system are with my oven.
That said - I can see that I can make improvements - and the right time to re-plumb everything is when I move it and rebuild the platen.

I'm hopeful that wider plumbing will make for quicker evacuation (and more detail).


jdougn wrote:

Concerning the platen, are you doing mostly one-off type pulls or production forming? If you're doing production consider mounting the mold/s to the platen to make release of the formed ABS faster & simple. That will dictate what type of platen you make and if it is as complex as the Proto-Form. The Proto-Form is excellent for prototype work but that's a lot different than production forming.


I think that it is safe to call what I do one-off.
Basically just making parts for myself or friends with a costuming addiction.
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knightshade
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Joined: 19 Jun 2005
Posts: 123
Location: Rochester NY

PostPosted: Mon Feb 28, 2011 11:24 pm    Post subject: Reply with quote

In talking with another tonight - it was mentioned that having the air evacuated too fast would lead to an increase in webbing....

Not something that I had considered...

Anyone have experiences?
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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Wed Mar 02, 2011 1:59 pm    Post subject: Reply with quote

If you're do the two stage you can always leave the handle to the tank partially closed to control air flow. On the molds I work with, there are many other areas that seem to cause webbing before rapid air flow becomes an issue. However, being able to control the rate of air movement is important and could lead to webbing.
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