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My 2 X 3 Design (pic heavy)
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felixx
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Joined: 21 Sep 2009
Posts: 68
Location: San Diego, CA

PostPosted: Mon Sep 21, 2009 2:49 pm    Post subject: My 2 X 3 Design (pic heavy) Reply with quote

First off I had a couple of questions on pulling strength.

I was at walmart yesterday and I happend to notice a 4.5 HP shop vac for 68 bucs. Would this be enough to pull a 2x3 table? I plan on using ABS for my first project so I was curious.

I have been a little busy designing my table.

Here is what i have so far:



click HERE for an animated version.

thanks for advice on suction

cheers
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spektr
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Joined: 07 Jan 2008
Posts: 415

PostPosted: Mon Sep 21, 2009 3:52 pm    Post subject: Opinions Reply with quote

You will find many opinions here. Some are better than others. I have been criticised by some for being overly conservative. However that also means my stuff works. It might not be the cheapest or simplest, but it is always functional.

I truly believe you dont know enough about the process yet. You are asking if a vacuum cleaner can pull ABS. Under ideal situations yes.. In practicality you haven't got a chance of geting it to work. There isnt enough Delta P (differential pressure) provided by the vacuum cleaner
to make the bulk of things happen. You probbly would be able to pull styrene in thin sheets.

Study some stuff, and get a feel for whats going on. When you come back, you'll be able to get your questions answered because you will have better questions..

I dont mean to seem blunt or rude, but studying the procewss a bit will pay huge dividends.....

Scott.
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felixx
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Joined: 21 Sep 2009
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Location: San Diego, CA

PostPosted: Mon Sep 21, 2009 4:00 pm    Post subject: Reply with quote

Just to let you know, I took no offense to your response.

I think it may have been my wording and lack of content that I left out.


I have been working on a 2' x 3' with a tank and pump at a friends place using abs. I know that abs tends to be a bit rubbery meaning it can try to force its way back to flat if it doesnt get hot enough or its not pulled right.

I felt that my question particularly regarding the "4.5" shop vac, versus lower grade ones, would do the job. I may have a pump, but still looking for a tank, I thought that I could use a shop vac as a temp set up until i was able to find a tank to use.

The table I worked on was the ideal setup in my opinion, the heat was above, and the pull lever right in front. I have pulled probably 15 to 20 sets of armor which in my opinion, give me the "feel" of how to operate and know the plastic a little.

Anyway, thanks again for your feedback Scott

cheers
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spektr
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PostPosted: Tue Sep 22, 2009 7:15 am    Post subject: Reply with quote

Outstanding..

Heres the problem with shop vacs. They flow a LOT of air at low vacuum levels. The HP designation on the vacuum cleaner has to do with the CFM it will flow. More HP means more CFM. The actual vacuum will be nearly identical between the 2 units because the impeller design used to generate the vacuum "stalls" at a much lower vallue than most plastics need to see, unless it is fairly soft thin plastic.

ABS at 1/8th inch will need to heat a fairly long time (compared to your past armor) to get the heat all the way thru the sheet without burning the first side. Dwell time is your friend. You will need to get the oven output controlled to a lower level or space the oven further away from the frame. Shielding the perimeter of the oven will be necessary as well as maybe screening the oven center to balance the heat load across the plastic surface. A 2 x 3 oven isnt too tough to get balanced, thankfully.

As far as pulling the plastic, there is merit to using a vacuum cleaner as part 1 of a 2 stage process, but I just dont mess around with it that way because I have enough tank and pump to make it easy on myself. The tank is important, it allows you to move a lot of air fast. It also allows you to get high vacuum on the part quickly. These are important things as I find most failures to mold are caused by inadequate vacuum/cfm not pulling tight ot the mold details.

ABS itself has a few quirks. It varys a lot from lot to lot. Toodays sheet will process a bit different than last months material. Sometimes better, sometimes worse. As a result of that, you wont be able to EXACTLY nail down the process, you'll need to get a feel for what the sheet is telling you. You;ll always stay close, BUT tuning the first couple pulls could be a small adventure..

TOOLING. Your molds need to withstabd a fair bit of heat transfer as ABS cools slower than styrene. I like cast urethanes, epoxys and cast aluminum. Your sheet carriers/frames will need teeth to prevent slippage out of the sheet carrier on prestretch.

These are just a few random thoughts, but maybe they help.....

Scott.
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jdougn
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Joined: 18 Mar 2009
Posts: 702
Location: Louisville KY area

PostPosted: Tue Sep 22, 2009 8:13 am    Post subject: Proto Form vac former Reply with quote

Hey Felixx, welcome to the boards!

What kind of projects do you anticipate? I noticed you've already done some work pulling armor. Are the picts in your signature work that you've done?

I run a shop built 2'x4' vac former pulling 1/8"-1/4" ABS. My suggestion would be to take a look at the Proto-Form vac former plans at Build-Stuff.com and the related builds posted on this forum such as the one by TD1035 2x4 Proto-form build...HERE WE GO!!!!

I built my own machine, using advice mainly from this forum, without plans. However, even though I spent hours & hours on research and design the machine still needed reworking & redesigning in many areas. I would've saved money & time getting the build-stuff plans and probably have a better vac former!

Scott may be blunt in his approach but he has extensive knowledge to back up his advice. His advice to use a real vac pump & storage tanks is correct. In my experience, if the vacuum drops below 15-20inHg (inches of mercury) then the ABS tends to not hold shape correctly and the pull fails. A shop vac is just not capable of getting to that level of vacuum. Harbor freight sells some inexpensive vac pumps. Harbor Freight Tools - 9cfm Vacuum Pump or you can always search eBay for a professional quality Gast Vacuum Pump. Used water heater tanks are also good & cheap. You might try using a shop vac on your machine to see how it works and then upgrading to a vacuum pump & tank/s as needed.

Post up some picts of your stuff when you get the chance! It's always good to see the progress and ideas that users are working on!

DougN
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jegner
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Joined: 30 May 2003
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Location: Texas, USA

PostPosted: Wed Sep 23, 2009 8:32 am    Post subject: Reply with quote

When I started I wanted to test my machine with some cheap plastic just to see what all it could pull. It's been my experience that a 6.5hp shop vac is good for thin HIPS, up to about .093. .060 and .080 is a good thickness upper limit for molds with a lot of detail.

For PETG or ABS or Lexan, a high-vac or at least a 2-stage is necessary to pull thicker materials.

IMHO

Jim
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felixx
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Joined: 21 Sep 2009
Posts: 68
Location: San Diego, CA

PostPosted: Wed Sep 23, 2009 12:35 pm    Post subject: Reply with quote

Good news!

I just scored a Gast Pump!

the 1023 series.

Just got off the phone with Gast to ask them specs on it, and I also grabbed the pdf file on it.

26.5 mercury, 10 cfm

now all i need is a 30 gallon tank Smile (or smaller)

jdougn wrote:


What kind of projects do you anticipate? I noticed you've already done some work pulling armor. Are the picts in your signature work that you've done?




Post up some picts of your stuff when you get the chance! It's always good to see the progress and ideas that users are working on!

DougN



Hey Doug, In my sig the only stuff that i pulled was parts of the Animated ARF Clone, however I cant take credit for the sculpting. I was learning how to pull on a machine, get the feel of it on other projects and thought the concept was so great, I wanted to do a little research, which turned into a lot of research Smile

I have been sculpting molds for various armor pieces. Right now the ones that are almost ready are Parts for Vader. Im making two sizes. The standard size and a longer shin size for taller people.

I have talked to a handful of vaders who complain that their shins are too short and rub them on the kneecaps. So I figured this would be a good start. Nothing to big until I get comfortable Smile

In the future I am looking into other props, house hold items, parts for your car (dashboard etc.).

whatever road it takes me on Smile



On a side note, how thin of sheet metal should i go to put on top of the pulling surface?
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jdougn
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Joined: 18 Mar 2009
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Location: Louisville KY area

PostPosted: Wed Sep 23, 2009 7:29 pm    Post subject: Reply with quote

Felixx, congrats on the Gast Pump, especially a 1023! As far as tanks go, get as big & as many as possible! If a small fail happens during the pull then tank volumn can save the pull. I had a commercial vac forming shop do some work for me and their vac former tank held over 1000 gallons!

Sounds like you're doing your homework on figuring out what parts to make. Find a need and meet it! Somebody said that all you have to do is improve a part by 10% or decrease the cost by 10% and you'll have a market.

I really don't know what gauge sheetmetal do use for a planten top. To do proto-type work you'll need a generic perforated planten. My vac former uses a plastic sheet with an aluminum skin bonded to it that I picked up at a local flea market and it has worked well. If you look at TD1035's build you'll see hardware cloth (heavy duty screen) underneath the skin to provide overall consistent support. The Proto-form by Doug Walsh may use a stainless steel skin. Regardless, I'm pretty sure they get it bent to shape and don't do that part themselves.

hth, DougN
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felixx
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Joined: 21 Sep 2009
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PostPosted: Thu Sep 24, 2009 4:33 pm    Post subject: Reply with quote

Note to self:

2x4's and 2x6s are actually 1/2 x 3 1/2 and 1/2 x 5 1/2

blasted!
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jdougn
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PostPosted: Thu Sep 24, 2009 5:22 pm    Post subject: Reply with quote

felixx wrote:
Note to self:

2x4's and 2x6s are actually 1/2 x 3 1/2 and 1/2 x 5 1/2

blasted!


I take it you're not a carpenter? That's what I do so I can afford to build my vac former & buy more plastic! Actual versus nominal dimensions!

dn
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felixx
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PostPosted: Thu Sep 24, 2009 5:32 pm    Post subject: Reply with quote

its ok, i caught it before it was too late Smile

UPDATE:

Okay a few pics. After a slight setback I managed to get to a stopping point.


The Lumber, eventually I had to go get another 2x4, 1 1/2 x 3 1/2 lol (what can I say, I grew up in a machine shop, not a wood shop)


The bottom frame (before setback)

Correct size frame with upright supports attached.

Stopping point until i get a few more pieces. Bottom shelf, and top. I will be using 1/2 inch plywood for both (unless anyone can suggest another type of wood.

Ill post as I go, cheers!
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jdougn
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PostPosted: Sat Sep 26, 2009 7:26 pm    Post subject: OSB might work too Reply with quote

felixx wrote:
its ok, i caught it before it was too late Smile

UPDATE:
Stopping point until i get a few more pieces. Bottom shelf, and top. I will be using 1/2 inch plywood for both (unless anyone can suggest another type of wood.

Ill post as I go, cheers!


Looks like a great start for the support frame! For the shelf, 1/2" sheathing grade plywood may sag over time just a little but it should do okay in general. You might find that 5/8" OSB is about as expensive and it would do better. Regardless, you're working the plan and you'll get there.

Good Start!
DougN
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felixx
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Joined: 21 Sep 2009
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PostPosted: Sat Sep 26, 2009 11:29 pm    Post subject: Reply with quote

i dont want to ever worry about future sagging. I was looking at craigslist today and saw a few oak desks under the "free stuff" section. For free, heck ill saw it to size Wink

still considering it, i know it would make it that much heavier.

I bought my MDF today for the pulling surface today. Im pretty excited, tomorrow i go pick up the 1023 pump Smile
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felixx
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Joined: 21 Sep 2009
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Location: San Diego, CA

PostPosted: Tue Sep 29, 2009 6:51 pm    Post subject: Reply with quote

Got the pump Sunday



came with this as well,



i promised the guy who gave me the pump that I would hook him up big time for passing it down to me. It works great!

will be working on the pulling surface soon. got the mdf for top and bottom, just need a 1/8 piece to put between, sheet metal and start drillin holes.

its going to be A LOT of holes...

Thats all for now
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spektr
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PostPosted: Wed Sep 30, 2009 6:48 am    Post subject: Nice Pump.. Reply with quote

Felix,
Cool pump.....
When you make the platen, I 'd suggest a lot taller spacer than 1/8th inch.
You will greatly reduce flow. Vacuum is not like pressure, flow obstructions are a lot more important. If you don't have at least an inch of space , you'll see the differences in process times. I know the the plenum evacuation volume looks substantial, but reducing it below a critical point really kills flow. I know 1 inch functions well, I also know 1/8 inch doesn't. Somewhere in the middle might also be fine, but with that pump, I'd go to the known good size @ 1 inch.......

Scott.
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