Vacuforming Questions

Flintlock

Sr Member
Even though I've been involved in researching SS kit donor parts since '97 or '98, I'm really not that experienced in scratchbuilding. I wanted to know some things about vacuforming.

I've never vacuformed before, and I live in a very small studio apartment. What should I watch out for so I don't let the plastic melt down onto the heating element in my stove and start a fire? :lol After I do it a couple of times I should have enough of a hang of it to do it more. But I don't want to screw it up the first couple of times.

Has anyone tried to vacuform plastruct gray ABS sheet? How's it work out? From what I've seen it's very, very nice for scratchbuilding. But I suppose Styrene is a bit cheaper.

I've learned that the size of the Plastruct hemisphere for the SS TIE Fighter is 5 1/4". Before I thought it was 5" and was hoping to pick up some 2.5" hemis to make a 1:48 TIE. Then I was disappointed, but then I found some 2 5/8" hemispheres (right size for studio half-scale). These hemis are made out of 'virgin' High-Impact Polystyrene, and are really nice for this project. But I need to vacuform over this shape to build the rest of the ship.

Is this possible? Will the heat from the softened sheet warp the hemisphere? Again, it's 2 5/8" diameter and about 1/16" thick.

By the way. The fact that the SS TIE hemi is 5.25" in diameter has some interesting consequences. The Fine Molds TIE marked as 1:72 is too small. It's about 1:100, and the "1:48" I would imagine is still too small. The ERTL Darth Vader TIE Fighter (whose wings and front window frame are used on the SS TIE Bomber) is 1:48, almost exactly - half studio scale. Which would make the TIE Bomber also 1:48, and would make this kit roughly in-scale with the ERTL X Wing. The AMT TIE Fighter double-pack and TIE Interceptor kits are also too small for 1:48. Those kits and the 1:48 TIE from Fine Molds (probably) are about 1:72.

Anyway, any help, advice, vacuforming wisdom would be appreciated. Thanks!
 

Dung0beetle

Well-Known Member
I don't believe it to be an issue because the hot styrene will cool very quickly. Your oven needs to be about 200° - 25O° F (120° C). Use a thermometer, don't trust the oven knob. I don't have much experience vac-forming items that small, but you can start with a lower temp and gradually increase the temp. until the material begins to deform.

I don't recommend heating plastics indoors, because they tend to give off toxic fumes. As long as you stay under about 400°, the fumes shouldn't be much of a factor.

I hope someone more experienced will chime in and lend more expert advice. Good luck with your build.
 

Flintlock

Sr Member
I don't believe it to be an issue because the hot styrene will cool very quickly. Your oven needs to be about 200° - 25O° F (120° C). Use a thermometer, don't trust the oven knob. I don't have much experience vac-forming items that small, but you can start with a lower temp and gradually increase the temp. until the material begins to deform.

I don't recommend heating plastics indoors, because they tend to give off toxic fumes. As long as you stay under about 400°, the fumes shouldn't be much of a factor.

I hope someone more experienced will chime in and lend more expert advice. Good luck with your build.
Thanks for the tips. There's no way I should need to get up to 400 degrees right?
 

Flintlock

Sr Member
Oh I had a few more questions.

What's the thinnest sheet you've been able to vac form with? Have you used any Plastruct ABS instead of styrene, and is it pretty much the same deal? Is there any significant change to the thickness of the sheet when it is formed over the buck?
 

3d-builder

Sr Member
Oh I had a few more questions.

What's the thinnest sheet you've been able to vac form with? Have you used any Plastruct ABS instead of styrene, and is it pretty much the same deal? Is there any significant change to the thickness of the sheet when it is formed over the buck?
There will be more change in thickness the taller the
pattern is ......I don't think you will have to much considering
the part your forming is basically half of a small globe and pretty
small. Form in the desired thickness you want and just see what you have
thickness wise when your done. If you feel you want it a bit thicker then
move up in thickness.
I don't think you need to form something like that in ABS the material
will be more expensive, the high impact polystyrene will be fine.Remember I by my sheets in 4X8 size, so maybe a small sheet from plastruct is very affordable I wouldn't know? If you think your going to do more forming in the future better to get a half or full sheet from a plastic distributor.
I use many thicknesses it doesn't matter you can form with paper thin,
but it has to SUIT YOUR NEEDS. The thinner the plastic the less time it needs to heat in the oven.
It will heat faster and cool even quicker, so it's important to have a quick smooth delivery to
the platen.


Regards,
Michael
 
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yuumi2891103

Sr Member
You are very lucky man Flintlock-san

Because you got the advice of Master modeler Michael 3d-builder aka Professor Vacuum forming :thumbsup
 

cavx

Master Member
RPF PREMIUM MEMBER
I didn't want to start a new thread given I have related questions.

I watched the Vac Forming video by Aram Batholl and he uses what appears to be a hand vacuum pump.

It looks like a bike pump, except it sucks not blows. Are these any good? If so, where would I get one?



In the video, he heats his plastic over the mold until it slumps, them makes the vacuum pull. Also his molds are negatives [hollowed out].



Is there any benefit over positives for this? Or is he doing this because the vacuum of his hand pump is not that great?
 

cavx

Master Member
RPF PREMIUM MEMBER
Another dumb question:

Can you Vac Form over a Vac Form?

I am guessing that if I Vac Form my part, trim it, but leave on the buck that I can pull another, now slightly larger version over the top. Is there any issues in doing this?

I am not concerned about loss of detail as there is none on the part anyway.
 

cavx

Master Member
RPF PREMIUM MEMBER
Another dumb question: Is there a way to work out how thin the plastic will become after Vacuum Forming? I get the more it has to stretch, the thinner it will be.
 

Thranduil

New Member
Another dumb question: Is there a way to work out how thin the plastic will become after Vacuum Forming? I get the more it has to stretch, the thinner it will be.
Generally speaking, as long as your piece is sized correctly, you should lose about half your starting thickness. The stretch causes most of this. The higher your platen (or depth if you prefer) and the smaller your framed plastic will result in thinner final.
If maintaining your thickness is critical, make sure you have a large piece of plastic. Too large and you'll get wrinkles (creases) along the sides. This is why some platens need to be built up with what is commonly termed "run off", so the part itself comes out correct and the wrinkles end up on the run off area instead.
I don't know if I've made this understandable, it's hard to express what really needs to be seen to be understood.
 

cavx

Master Member
RPF PREMIUM MEMBER
Generally speaking, as long as your piece is sized correctly, you should lose about half your starting thickness. The stretch causes most of this. The higher your platen (or depth if you prefer) and the smaller your framed plastic will result in thinner final.
If maintaining your thickness is critical, make sure you have a large piece of plastic. Too large and you'll get wrinkles (creases) along the sides. This is why some platens need to be built up with what is commonly termed "run off", so the part itself comes out correct and the wrinkles end up on the run off area instead.
I don't know if I've made this understandable, it's hard to express what really needs to be seen to be understood.
Thank you for answering the question.

The material becoming thinner makes perfect sense to me because there is a finite amount that is made to spread out further. It has to become thinner to cover the new, larger area. I guess some of this will be trial and error.

Would these wrinkles be the same as 'webs' that can occur between parts? I have seen where they lay coins or similar thin spacers to lift the buck off the Vac Form to allow the plastic to pull down past the buck and give a cleaner sharper edge - or more to the point, allow the radius that forms to be below the buck. No problems there.
 

3d-builder

Sr Member
Generally speaking, as long as your piece is sized correctly, you should lose about half your starting thickness. The stretch causes most of this. The higher your platen (or depth if you prefer) and the smaller your framed plastic will result in thinner final.
If maintaining your thickness is critical, make sure you have a large piece of plastic. Too large and you'll get wrinkles (creases) along the sides. This is why some platens need to be built up with what is commonly termed "run off", so the part itself comes out correct and the wrinkles end up on the run off area instead.
I don't know if I've made this understandable, it's hard to express what really needs to be seen to be understood.
Yup well said.....:thumbsup
 

3d-builder

Sr Member
This is a part I formed recently I formed it out of .093 just a hair under
3mm. My riser raised it 6mm off the platen, after forming the sides on the
formed part were a hair under 2mm.





Notice I taped off some of the holes on the platen....
to get a more centralized vacuum around the part.
Because the part has a lot of angels and drops,
and I don't have a secondary vacuum source like
a vacuum pump. I am trying to get the most draw
I can when the plastic hits the platen.

If I was using a thinner plastic i could expect
sharper lines on all those angles......but it's a
trade off, I also need enough meat left over to scribe
panel lines. The extra meat allows me to do that and
then just sand the angles sharp later on.
 
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3d-builder

Sr Member
Another dumb question:

Can you Vac Form over a Vac Form?

I am guessing that if I Vac Form my part, trim it, but leave on the buck that I can pull another, now slightly larger version over the top. Is there any issues in doing this?

I am not concerned about loss of detail as there is none on the part anyway.

Done it plenty times never had a problem.....
yea you will increase the size as you said.

When you start forming different shapes you
will learn a lot....you will begin to understand
the limitations of the process........well at least the
limitations at home! LOL The better you can set up
your rig the more you can expect. But you can still
do a lot and achieve nice results at home without
spending a mortgage payment.
 
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cavx

Master Member
RPF PREMIUM MEMBER
Done it plenty times never had a problem.....
yea you will increase the size as you said.

When you start forming different shapes you
will learn a lot....you will begin to understand
the limitations of the process........well at least the
limitations at home! LOL The better you can set up
your rig the more you can expect. But you can still
do a lot and achieve nice results at home without
spending a mortgage payment.
Awesome! I am so looking forward to my first Vac Form.

I did a suction test yesterday because I was having a doubt that the VAX Vacuum cleaner I want to use would have enough grunt. There is no sealing tape currently on my platen so I just laid a piece of 16mm MDF that just covered all the holes, turned on the suction and once the VAX went into overload, I could not pull up the sheet. In fact the whole platen lifted off the bench. I also sourced a proper 32mm vacuum fitting for this rig rather than just drilling a hole.

I found a heater that I think will work well. I just need to get down to the sheet metal fabricators to get some Gal to line the insides of the heating unit. I could use foil as James [XRobots] does on his video.

What should I be paying for a sheet of HIPS? One quote came back at $70 for 2400 x 1200 sheet of 2mm. Is that right or am I being taken for a ride here?

Oh and here is my rig. Any suggestions as to what I may have missed are welcome.



And with my first MDF buck [my acoustic tile]

 
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