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Mini-Vacuum Former

 
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propsculptor
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Joined: 24 Mar 2006
Posts: 22
Location: Southern California

PostPosted: Tue Apr 18, 2006 7:36 pm    Post subject: Mini-Vacuum Former Reply with quote

I recently started building a Mini-Vacuum Former to save on plastic, since many of my castings don't need to be the size of a facecast, I found in my Garage a Eureka Mini-Mite that looks something like this:

(And No it's not a New Vacuum, I already have a Big Shop Vac)

I gutted it last night and I'm converting it into a self-contained Vacuum Former, I'll post step-by-step photos once I've made some real progress.

For anyone that want's to make a similar one to save space in their shop, I found this little one cheaper than a new one (They are usually $107.00 or more):
http://www.sewserg.com/products/abp02083-1181.html
(This one is only $69.99)

This Mini-Vacuumformer will be perfect for small projects that are about 7 inches X 7 inches, the only thing I have yet to figure out is the best heating element, I could go with a portable Range top (Hot Plate) but I want to go with something more rectangular, if anyone has suggestions feel free to let me know. Very Happy
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ANH trooper
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Joined: 20 Oct 2005
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Location: UK

PostPosted: Wed Apr 19, 2006 2:50 am    Post subject: Reply with quote

To save on plastic when only forming small peices,I have made different sized platens that just sit on top of my former.

Basically they peices of wood with the weather stripping on with a pipe conected in the center.This slots through a hole on the table and connects to the vacuum.I have three sizes which arefor plastic sheet sizes 24"x24",24"x18" and 24"x12".

These are quickly changable and I had to make different sized frames to hold the plastic.They are made from wood but now I have made a new metal frame for my flip-top style former and have designed it so that I can still use the main clamping frame at 24"x24",but has inserts to be able to use smaller plastic.

If everything works out,I'll post pics.Fingers crossed..... Smile
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jegner
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Joined: 30 May 2003
Posts: 2099
Location: Texas, USA

PostPosted: Wed Apr 19, 2006 9:01 am    Post subject: Reply with quote

Great idea. I made an early vacuum form machine using a $25 indoor electric grill from Walmart. It had a 12x18 heating surface that might be just right for your needs. You would need to remove the thermostat, and rig up an electric switch though.

Keep us posted. I use my 24x24 frame machine exclusively now, and have considered making different size frames, but when I pull a part, I usually try to gang up other smaller parts to maximize the use of the platen and parts.

I would go with a 12x12 frame. This way you get 4 sections from one 24x24 inch sheet.
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propsculptor
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Joined: 24 Mar 2006
Posts: 22
Location: Southern California

PostPosted: Wed Apr 19, 2006 9:59 am    Post subject: Reply with quote

I have been planning on making a small Vacuum Former for making small parts such as Eyes, Mold keys, and other small parts, finding my old mini-mite Vacuum was just a lucky thing for me, so I started building it.

I'll post pics of my progress in a day or so.


As far as the Electric Grill, that's what I used for my first Vacuum-former,
I got it from Wal-Mart:
http://www.walmart.com/catalog/product.gsp?product_id=2555218

For anyone wanting to get one they are out-of-stock at the moment.
jegner wrote:
Great idea. I made an early vacuum form machine using a $25 indoor electric grill from Walmart. It had a 12x18 heating surface that might be just right for your needs.

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thebluecanary
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Joined: 02 Feb 2006
Posts: 123
Location: St. Louis, MO

PostPosted: Wed Apr 19, 2006 11:41 am    Post subject: Reply with quote

ANH trooper wrote:
To save on plastic when only forming small peices,I have made different sized platens that just sit on top of my former.

Basically they peices of wood with the weather stripping on with a pipe conected in the center.This slots through a hole on the table and connects to the vacuum.I have three sizes which arefor plastic sheet sizes 24"x24",24"x18" and 24"x12".

These are quickly changable and I had to make different sized frames to hold the plastic.They are made from wood but now I have made a new metal frame for my flip-top style former and have designed it so that I can still use the main clamping frame at 24"x24",but has inserts to be able to use smaller plastic.

If everything works out,I'll post pics.Fingers crossed..... Smile


Keep us informed! It sounds good. I picked up a book: Secrets of Building a Plastic Vacuum Forming Machine, Not the greatest book. Some interesting things, but it does talk/show how to make an adjustable blastic clamp.

Basiclly the vac table has a just a big hole in it, and all the little holes are on different sized plates. The locking clamps has an extra set of arms that slide left to right and these are what hold the plastic and clamp it down.

Confused? Yeah, thats why they have pictures in the book. =P
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propsculptor
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Joined: 24 Mar 2006
Posts: 22
Location: Southern California

PostPosted: Wed Apr 19, 2006 8:05 pm    Post subject: Reply with quote

I'm just wondering what a "blastic clamp" is? Laughing

I bought the same book for $6.00 from another website, but I found the information better in the book: The Prop Builder's Molding and Casting Handbook
(Click on the title to get the book)


thebluecanary wrote:
ANH trooper wrote:
To save on plastic when only forming small peices,I have made different sized platens that just sit on top of my former.

Basically they peices of wood with the weather stripping on with a pipe conected in the center.This slots through a hole on the table and connects to the vacuum.I have three sizes which arefor plastic sheet sizes 24"x24",24"x18" and 24"x12".

These are quickly changable and I had to make different sized frames to hold the plastic.They are made from wood but now I have made a new metal frame for my flip-top style former and have designed it so that I can still use the main clamping frame at 24"x24",but has inserts to be able to use smaller plastic.

If everything works out,I'll post pics.Fingers crossed..... Smile


Keep us informed! It sounds good. I picked up a book: Secrets of Building a Plastic Vacuum Forming Machine, Not the greatest book. Some interesting things, but it does talk/show how to make an adjustable blastic clamp.

Basiclly the vac table has a just a big hole in it, and all the little holes are on different sized plates. The locking clamps has an extra set of arms that slide left to right and these are what hold the plastic and clamp it down.

Confused? Yeah, thats why they have pictures in the book. =P

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thebluecanary
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Joined: 02 Feb 2006
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Location: St. Louis, MO

PostPosted: Thu Apr 20, 2006 7:10 am    Post subject: Reply with quote

Thats funny! I bought that book at the same time as the other one. Amazon gave a discount if I bought them both, and free shipping. Yeah, I think I paid about $6 for it as well.

propsculptor wrote:
I'm just wondering what a "blastic clamp" is? Laughing

I bought the same book for $6.00 from another website, but I found the information better in the book: The Prop Builder's Molding and Casting Handbook
(Click on the title to get the book)


thebluecanary wrote:

Keep us informed! It sounds good. I picked up a book: Secrets of Building a Plastic Vacuum Forming Machine, Not the greatest book. Some interesting things, but it does talk/show how to make an adjustable blastic clamp.

Basiclly the vac table has a just a big hole in it, and all the little holes are on different sized plates. The locking clamps has an extra set of arms that slide left to right and these are what hold the plastic and clamp it down.

Confused? Yeah, thats why they have pictures in the book. =P
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drcrash
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Joined: 04 Sep 2006
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Location: Austin, Texas

PostPosted: Tue Oct 03, 2006 12:01 am    Post subject: major suckage from tiny vac Reply with quote

Quote:
I recently started building a Mini-Vacuum Former to save on plastic, since many of my castings don't need to be the size of a facecast, I found in my Garage a Eureka Mini-Mite [...]
I gutted it last night and I'm converting it into a self-contained Vacuum Former, I'll post step-by-step photos once I've made some real progress.


Propsculptor, did you ever post anything more about this?

I just got a little hand vac at a thrift store for $5, and it has an 8 amp, 1000-watt motor---about 2/3 the amps of my 5.5 HP shop vac, but about a tenth the size. It's a Shark Ultra. (The current Shark hand vacs are apparently not quite as powerful, with 700 and 800 watt motors.)

I did some tests, and it seems to pull about as hard as the shop vac. (The shop vac is no slouch; it can suck water at least six feet of water up its hose, so I guess it's doing several inches of mercury or a few PSI.)

I'll do more precise comparisons when I get the vacuum gauges I just ordered. (My comparative tests so far consist of seeing how far a vacuum can pull craft foam down into a 1-inch diameter tube.)

BTW, the 8-amp Shark is considerably more powerful than my 4-amp Dirt Devil. (The Dirt Devil clearly doesn't pull as hard as the shop vac, making a shallower dimple in the craft foam.)

I'm sure the little Shark vac can't do nearly as many CFMs as the shop vac, but once the air's mostly out, it can pull about as hard. For a small table, at least, it should be fine and get similar detail to the shop vac. I'm planning to build it into my little Sunbeam over-and-under.

I guess the moral of this story is that you shouldn't assume that a big shop vac actually pulls harder than a regular vac, or even a little hand vac. Lots of regular vacs these days have 8 to 12 amp motors, so they should perform similarly to big 12-amp shop vacs if the impellers are designed right.
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drcrash
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PostPosted: Tue Oct 10, 2006 5:51 am    Post subject: Reply with quote

Ok, I got my vacuum gauges, and the little 8-amp Euro-Pro Shark hand vacuum is definitely comparable to the 10x larger shop 12-amp shop vac.

In fact, it sucks almost an inch of mercury harder. (A little less than four for the shop vac---how disappointing---vs. almost 5 for the hand vac.)

Wow. I guess I know which one I'll be using for the little over-and-under rig.
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jegner
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PostPosted: Tue Oct 10, 2006 7:25 am    Post subject: Reply with quote

Yes, shop vacs no matter how stout really are only able to pull between 4-6 inches of Hg. You can run two, one pulling through the other, and get 50% more output, but a better option is to reduce the size of the hose.
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drcrash
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PostPosted: Tue Oct 10, 2006 8:38 am    Post subject: Reply with quote

I'm beginning to wonder if small vacs will systematically tend to suck harder than large ones, if they have similar amperage motors.

I got to thinking about that when I first saw the little Shark vac. I was wondering what the heck you could do with an 8 amp motor in such a little package, sucking through such a little hose. (Smaller than the small shop-vac hose size.)

It seems to me that if you're sucking through a small hose, it's useless to try to pull a lot of CFMs. The resistance of the hose goes way up as the hose gets small, so just the load from the hose and any attachment would likely defeat any attempt to pull high volumes at low force. Most of the extra amps would just go to waste.

So for the same amount of work, you'd be better off designing a high-torque system that pulls lower volumes but with higher vacuum. Otherwise your small hose and attachements will just hose you, CFM-wise, and you won't get harder suck either.

So maybe when looking for vacuum cleaners, we should be looking for small-hose machines with high amps, like Propsculptor's little Eureka canister vac. They may do a better job all around than big shop vacs, especially if we're making the shop vac suck through a small tube, which it isn't designed for.

Unfortunately, there are a lot of variables here and no useful specs.

Quote:

Yes, shop vacs no matter how stout really are only able to pull between 4-6 inches of Hg. You can run two, one pulling through the other, and get 50% more output, but a better option is to reduce the size of the hose.


It doesn't seem (at first glance) like a small-diameter hose would help, except by reducing the volume of air in the hose that must be sucked out. And if internal volume is the problem, the body of the shop vac is a bigger culprit---the 12-gallon-or-so buckets of most big wet/dry vacs have a lot more volume than the hose, and they suck the air through that bucket.

The answer to that would be to get rid of the bucket---just use the lid of the vacuum (with the motor and pump in it) on some much lower-volume thing with a hose coming out of it.

My motor/pump pops off my shop vac, and can be used as a leaf blower.
I'm thinking of putting a bowl over the intake vents, with a flange on it, to capture the vacuum. Then I could get rid of the huge worse-than-useless bucket.
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jegner
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PostPosted: Tue Oct 10, 2006 8:49 am    Post subject: Reply with quote

Doug's book talks about doing just that, taking a vacuum motor, and making a box housing just big enough for the vacuum motor. The smaller the DIA of the hose does tend to help. Just look at some of your fittings, the smaller the inlet, the more pulling power the attachment seems to have. [to an extent]. One does tend to reach a point of diminishing returns, though.

CFMs aside, my 6.0hp shop vac can pull .125 acrylic and still get enough detail to show flaws in my molds, the only real difference I can see is to use the HIVAC set-ups for ABS or PETG or other slow to cool down materials, where the shop vac's just can't keep up.
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drcrash
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PostPosted: Tue Oct 10, 2006 9:14 am    Post subject: Reply with quote

Quote:
The smaller the DIA of the hose does tend to help. Just look at some of your fittings, the smaller the inlet, the more pulling power the attachment seems to have. [to an extent].


If I understand the physics right, and I may not, this should only be true right at that narrow fitting's orifice, or maybe briefly true just after you've sucked the plastic down.

A narrow fitting increases the velocity of the air at that point, but creates resistance, decreasing the overall airflow.

As I understand it, forcing the air through a narrow fitting won't help, unless that narrow fitting is right where you need the suckage, e.g., if you were pointing the narrow fitting right at the particular spot in the plastic that you needed to suck down. But the normal thing is that the table spreads the vacuum out again, so it won't help.

And the narrow fitting shouldn't make it achieve any higher final vacuum. The final vacuum should be the same no matter how big or small the opening is---it's just determined by how how much resistance the motor can overcome, inside the pump. Narrower fittings connecting to the table will just delay the point at which it tops out at its maximum pressure differential across the pump.

The exception to this is a brief moment when you stop up the fitting, or the plastic sucks down and the air pressure under the plastic suddenly strarts dropping.

(Before the plastic is sucked down almost all the way, there's little resistance, and not much difference in air pressure over and under the plastic. Once the plastic hits the table and the mold and the big air pockets are sucked out, suddenly there's resistance from the hard-to-bend little parts of the plastic that must be sucked into little gaps.)

At that moment, the inertia of the air in the hose may matter---it's going pretty fast through the hose, and can't stop on a dime. So it will tend to keep going, and maybe suck the air behind it along extra-hard momentarily. But once you've passed that point, and the motor is straining to significantly rarefy the air under the plastic and build up significant vacuum there, it won't help.

Something interesting happened when I tested the little Shark hand vac.
After I plugged the hose, the air pressure inside dropped pretty quickly and steadily to about 3.5" less Hg. Then there was a little pause where it seemed to top out, the pump whined louder and higher, and it crept up another half inch of Hg. Then another pause, another increase in whine volume and pitch, and it crept up another half inch of Hg. It seemed kinda like it was shifting gears, twice, to get a bit more torque.

That didn't happen with the shop vac... maybe just because the large internal volume acts as a big buffer, preventing any sudden transitions like that.
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