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        Question Vacuum forming

#1 Jerome Morris Nov 15, 2012 07:24 AM

Vacuum forming
 
How do they get large sheets heated (like for a hull) before putting over the hull?

#2 patmat2350 Nov 15, 2012 08:10 AM

Commercial machines have a movable frame to hold the plastic sheet. Either slides or flips between two positions... position 1 is next to a heater array; flip to position 2 to let the frame seal the vacuum and pull the still-hot plastic over the mold.

Note that heavier plastic is actually easier to work-- it doesn't cool off so fast in the seconds it takes to run the process.

Here's a big home-makable unit... the heater appears to be in the top, and the frame moves up and down.

http://www.build-stuff.com/images-pl...um-drawing.jpg

#3 der kapitan Nov 15, 2012 10:28 AM

I remember years ago, that a guy did some light vacforming with his oven and a vacuum cleaner. He made up a wood frame to hold the plastic.

There were drawings for a homemade vacformer available on the internet a while back, suitable for small parts.

#4 ken_nj Nov 15, 2012 10:47 AM

For small parts...

http://www.rcgroups.com/forums/showthread.php?t=1306908

#5 craig_c Nov 15, 2012 12:36 PM

Might want to check out this guy, Shawn Thorsson.... Just a normal Navy reservist with on heck of a hobby and an even cooler garage workshop.

A lot of what he does is accomplished with VacUForm and molding.

There is a shot of part of his VacUForm set-up on his blog (here). I know its not boating, but there no shame in using tech from other areas to build boats.

#6 dostacos Nov 15, 2012 08:35 PM

When we first started vacuforming in orhtotics we used B17 oxygen tanks for the air reservoir and heated the plastic in a pizza oven. the plastic held between 2 metal frames and a wooden base with holes was set up above the oxygen tank. the mold sat on the wooden table and the plastic was flipped over {the frame was suspended in the oven so the plastic could sag} pulled down over the wooden base, flipped the lever and sucked out the air. AND that is when we found out that regrind plastic led to inconsistent plastic thickness :eek: oh did I mention that we made a video to share with the entire orthotic/prosthetic field and ehem... had a well built young lady kinda streaked the room:rolleyes: the most popular training video ever in the field.

we also drape molded by putting the plastic on a metal plate with holes, sanded smooth and sprayed with a separator one person held the plate above the mold and the second layed the plastic on the mold, the plastic would go all the way around the mold and the plastic sealed to itself,

now back to your regularly scheduled posts....

#7 Jr Branham Nov 15, 2012 09:13 PM

mine
 
Here is a link to mine from years ago. Click on the video to play. It is the above mentioned machine..Proto-Form

http://www.rumrunnerracing.com/fefor...ad.php?t=23151

Not sure what happened. There was a video there, but now it's gone????

#8 Umi_Ryuzuki Nov 15, 2012 10:38 PM

1 Attachment(s)
Mattel Vacuformer...

I got to try one for a while... it was heat heat heat heat heat,...
then flip and pump for your life! The "toy" uses a hand pump.

If doing small parts in light plastic, it's okay, but it wasn't big enough for 1/72 turrets.

#9 WallaceConway Nov 16, 2012 12:47 PM

Vacu-Forming...
 
I had my own thermal formers years ago. The sizes I had were
1'X1', 2'X2', and a 2'X4'. The only real issue I had was heating the material. On the 1 footer. I used 5-100 watt light bulbs. This arrangement worked okay, but wasn't very fast. I later purchased a 110volt counter top hot-plate. I set it up to be about 18 inches under the plastic. Other wise the shape of the coils was the heating pattern on the plastic. Couldn't figure out why that happened. Later I built a diffuser to slip in at the half way point. Took care of that problem.
The 2 footer I used 2 1500 watt space heaters, placed them about 18 inches below the material, installed a diffuser. And that worked right off the bat. Both of these machines I also had a lid to place over the top of the plastic to act as an insulator to retain the heat. The complete cycle from 'Clamping the plastic into the frame and removing a finished project was right at 2minutes. The 4 footer I had a heating element custom made for this machine. It operated on 220 volt. with a thermostat. But because the heating elements were above the plastic I did not use an insulator lid.
For vacuum, I used a vaccum vane pump with 25 gallon storage tank. I could pull about 20+ inches per cycle. I could get some pretty good detail. Sometimes if the plastic was to thin or to soft. I could pull a hole into the plastic. The thickest material I used was 1/8 inch. And I needed every inch of vacuum to pull that stuff!

#10 WallaceConway Nov 16, 2012 12:50 PM

Vacuum forming...
 
On certain projects, I would also heat the molds to slow down the cooling on the material as it was being pulled. This would buy you a few moments extra for a more detailed part.

#11 craig_c Nov 16, 2012 06:50 PM

Quick and pretty clean VacForming setup
 

#12 Jerome Morris Nov 17, 2012 06:55 AM

Can't seem to get the video running.

#13 craig_c Nov 17, 2012 11:15 AM

Hmmm sorry, works for me.... Here's the link to the YouTube page

#14 Jerome Morris Nov 18, 2012 07:09 AM

That works. Thanks!

#15 steamboatmodel Nov 19, 2012 09:24 AM

Years back I repaired some pneumatics on a industrial Vacuform machine. They had the plastic in frames like he showed in the video, but there were metal and quick clamp/release. The frames ran through a heater box almost like a pizza oven and when it was heated it was pushed by a pneumatic cylinder over the mold. It them was pulled down on the mold by another cylinder and the vacuum was turned on under it and air pressure applied to the top. The mold with the plastic and frame where then ejected from the machine and the operator placed another mold on the vacuum table and the cycle repeated. They had about 12 identical molds that they used. Someone had run into the machine with a forklift and twisted the frame, they had straitened the frame out but all the cylinders and limit and trip switches had to be aligned and set which was what I had to do. I would have loved to run some boat hull molds through the machine, but that was not allowed.
Regards,
Gerald.


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