Vacuum forming and mould making question

So I'm undertaking an Orbital armor build and I'm in the midst of planning/sample ordering etc. The visor to the Orbital helmet (below) is dome-shaped with a bevel/a few indentations.



In terms of process, I'm thinking the following:

1. Building a mould out of EVA foam, coating in super sculpey (1/2" thick) or some sort of clay, carving out indentations/bevels and smoothing out entire mold.
2. Using 3mm clear acrylic and vacuum forming over the EVA/sculpey mould, then cutting out/shaving off excess
3. Vacuum forming a second layer of red two-way mirror window film over the acrylic under layer
4. Finishing edges/mounting in foam helmet/etc

My major question: any forseen issues with my EVA/sculpey mould? Will it screw up the acrylic? Do I need to bake the sculpey first (challenging considering the EVA will melt)? If so, does that mean I should use fima or some air drying clay? Will the indentations show through accurately? I know they wont be hard edges, but I think it will still come out somewhat desireably.

If I'm crazy with the EVA + clay, any other ideas on how to make a decent mould for this?

Thanks!

Unless the Clay is hardened, it might not stand up well to Vac-Forming. I would be tentative about even oven backed Super-Sculpy withstanding the pulling process. Alos unsure how well EVA foam will stand up to the process.

When I Vac-Formed my two Mark Vs, I was very cautious at first that the forming process would destroy my bucks before I could get good pulls. My vacuum form bucks were my original pepakura/fiberglass pieces, however some of my pieces were sculpted out of that dense pink insulation foam becuase I was not happy with the pep pieces I had made at first. Even thought I had sealed the foam with Modge podge and added a layer of resin, I was still afraid that the forming process would crush the sculpts. So, what I did was to take initial pulls off all my parts in a very thin plastic that would require less heat and less suction power to pull.

The initial pulls at lower temp and suction power with the thin plastic worked, and did not destroy my sculpts. I then took those initial pulls in thin plastic and then reinforced them and backed them, and then used them as my vacuum form bucks for the thicker plastic.

There are a lot of potential problems with the idea.

The eva foam and sculpey won't be strong enough to vacuum form. You need to fill the inside with a heavy duty expanding foam or something. I usually do a wood backing, but there's no wrong way to do it so long as the support material has good structural strength. I've read that vac machines can supply in excess of 100 pounds of pressure (45ish kg?), so make sure a slim adult or regular teenager could stand on it.

Vac forming a second layer onto the previous layer can be risky, make sure you have a deep enough lift bed so you can keep the first layer from getting too hot.

Remember to bake the acrylic before you vacuum form it, acrylic builds up water and needs to be rested at 100ish degrees Celsius for 1-2 hours to bake out the water. Otherwise it'll boil out too quickly in vacuum forming and bubble out.

I've never seen anyone successfully vac form mirrored plastic. The metal in it tends to burn the plastic that's encasing it, and the metal doesn't get hot enough to actually pull. You get better results vacuum forming plastic and then laying mirroring in afterwards. If you can get it to work, let us know and supply pictures and materials, because every plastic supply store claims it's impossible. The way pros usually get mirroring is to own an iridium vaporizing chamber to apply the mirror coat.

If you want to see some good tutorials on a similar topic, look up Thorssoli's EVA (the h3 permutation) helmet build. He vacuum forms and mirrors the gigantic visor it has. This stuff isn't impossible, but it does take some careful planning, which you are doing, so you're halfway there!

Edit: I finally found his pictures. Hopefully the link works for everyone else.
http://www.flickr.com/search/?q=eva&w=8050182@N06&adv=1&mt=all&ct=6&m=tags

@cadet & @katsu

Thanks this helps a lot. A few points/additional questions:

1. The reflective window film i have in mind is similar (I hope/think) to a window tint, which can be vac-formed. So no metal sheet or anything (it's also very thin, a film). But good point on the metal/heating issues. I might not have been clear in my original post.
2. It sounds like a main issue is going to be sturdiness. I like the resin/great stuff idea. So perhaps I'll try eva foam, seal it, great stuff/re-enforce interior of it, resin it, and go from there.
3. Noob question: what are bucks?
4. Re: baking acrylic - i was aware of a pre-bake to enable vac forming, but i didn't hear about "baking water out". Do you have any resources you could point me to about this?
5. I've actually seen that EVO helmet build before. My one issue is that it wasn't all one see-thru piece.

Thanks again for the help. Results won't come for a few months, kicking off undersuit build first, then armor, helm is last.

"Bucks" are the term for the Positive Mold you are pulling your plastic down over.

I agree that in 10 years working with Vacuum forming I have never seen anyone successfully pull a mirror reflective surface. I don't think I've ever seen window tint vac formed either. I'd be afraid it would crinkle, shrink, and/or melt. I would definitely suggest sticking to the "Dye Bath" or layering in the reflective surface with airbrush paint or another type of specialized paint.

If there are Pep files available for the Orbital helmet, what I would suggest is doing the pep build with the visor in place. Once you have fiberglass and strengthen the visor, you can then cut it out of the helmet and use that as your buck. It guarantees that the visor will fit your helmet, and you can carve the details like the beveling and indentations into the Bondo or Rondo or whatever filler you use.

I have never pulled Acrylic before, only ABS and Styrene materials. I would recommend attempting to find a clear plastic similar to what Thorssoli used, or Sean Bradley uses for his ODST visors, and try to avoid Acrylic if you can.

Acrylic is a pain in the butt to vacuum form, not sure why you're asking me for sources but:
http://en.wikipedia.org/wiki/Vacuum_forming
http://www.mtm-inc.com/reduce_project_risk/plastics_in_vacuum_applications/
Look at the common problems section, it's the second sentence.

There are some problems encountered in the vacuum forming process. Absorbed moisture can expand, forming bubbles within the plastic's inner layers. This significantly weakens the plastic. However, this can be solved by drying the plastic for an extended period at high but sub-melting temperature.

Click to expand...

PVC are examples of plastics which are not hydroscopic, while nylon, polycarbonate and acrylic are hydroscopic and should be avoided.

Click to expand...

Acrylic sucks in water from the atmosphere (hydroscopic), which causes that problem, it is also why a lot of people will completely avoid using it if possible.

As for the EVA helmet, the first draft he did was partially non-see through, but if you looked at the link, you will see the second draft is fully transparent (there is a shot of him licking the inside because he's awesome) Specifically these pictures:
http://www.flickr.com/photos/805018...LDt-8E1LtH-8E1LBK-8E1LA2-8E4ULd-8E1LGM-8DN4Uw

http://www.flickr.com/photos/805018...LtH-8E1LBK-8E1LA2-8E4ULd-8E1LGM-8DN4Uw-8DN4XN


Here is my acrylic visor, if you look carefully, you can see it's actually fizzing and bubbling as the water was boiling in the plastic, I intentionally didn't bake it to see what happens:


A successful pull in polystyrene:


And a picture of a vacuum forming buck before pulling it out of its tomb:


There are other plastics that can be vacuum formed for easier results, but if you can properly prepare and pull acrylic, it will give very nice results, I am not saying to not use Acrylic, but be aware that it is a lot more involved to properly pull than other plastics.. Practicing on PETG or Polystyrene is a cheap way to check for draft line problems, as acrylic is also more expensive generally.

Thanks - just wanted sources as I hadn't read that about that before. So thank you, very helpful.

PETG seems a great "starter" option, I'll definitely be looking into that.

I've seen a few video tutorials of people vac-forming dark window tints onto things like tail lights, so I'll try it and see how it goes. Could be a total failure.

Thanks for posting those pics, your original link didn't work for me for some reason. His mirroring technique may be an awesome backup if my tint idea doesn't work out.

As I'm reading, a wooden buck seems to be a commonly used thing, but people use those computer rotary drills (probably not the name) to form them, like the pic you posted. I have some buddies who work in a machine shop who I might be able to get access to one, but if not, do you think something like balsa would hold up as a mould? Reason why I ask as I remember it being easier to hand sculpt than other woods.

definitely interesting, so instead of using wood could you make the mold out of fiberglass and bondo and vacuum form over that?

I have made bucks out of wood. You can hand carve them, or use a ShopBot or other CNC rotary table (I used a shopbot). I've also made a fiberglass one for my Biker Scout visor, as well as doing one from pepakura. The pep one is a good way to make sure it will fit the helmet. You carefully cut out the visor of the helmet after pepping and rondoing it (You can't cut it out before, or it will warp and not fit the helmet after rondoing), then you fiberglass back it and do something to make it flat on a surface (glue a wood block to its underside, or expanding foam).

We've done successful vacuum form pulls off the wood shopbot, as well as the two different fiberglass ways I've done. The wood is the best option, but you'd need a buck cut. Pepakura is a great non machined option.

This visor was cut out of my mk5b helmet, wood backed and vacuum formed with PETG:









This one was 3d printed and then vacuum formed:

so lets say i want to vacuum form and make a buck out of this visor

how would i put all the details into that with rondo? would i just build it up then cut it down everything but the raised areas? and for the texture would i try to make it as smooth as possible after the rondoing? like wet sand with 1000 grit, would that make the visor have the smoothest finish? and can i wetsand the visor after forming it with 2000-3000 grit to make it like glass.

(i do alot of painting and work with sanding and painting car stuff)

and yet another question, for the specialized paint do i use an airbrush or just spray it on. im guessing nightshade but it would be super dark... tint would be ideal or could i possibly use the trick lightly coating it in plastidip to make it look black!

@katsu - thanks again. I've def got a few options. Not tackling this for a few weeks, but I wanted to get ahead of it. I'll make an update here when I've tried a few things.

shotgun rumble said:

so lets say i want to vacuum form and make a buck out of this visor

how would i put all the details into that with rondo? would i just build it up then cut it down everything but the raised areas? and for the texture would i try to make it as smooth as possible after the rondoing? like wet sand with 1000 grit, would that make the visor have the smoothest finish? and can i wetsand the visor after forming it with 2000-3000 grit to make it like glass.

(i do alot of painting and work with sanding and painting car stuff)

and yet another question, for the specialized paint do i use an airbrush or just spray it on. im guessing nightshade but it would be super dark... tint would be ideal or could i possibly use the trick lightly coating it in plastidip to make it look black!

Click to expand...

I would probably use a mix of rondo and bondo for that. It depends on what your base is - will this be pepakura cut out of the helmet (after rondoing the inside), or scratch made?

The first option is better as it ensures the visor will fit later. When doing outside details, bondo is for smoothing and such, rondo is for building up large areas. Check out Cereal's video on detailing halo armor:
http://www.405th.com/showthread.php...-Chief-**-A-Step-By-Step-Tutorial-(My-Way)-**

This gives a more visual idea of what you're supposed to do. But a lot of it depends on getting a good pepakura piece to serve as the backbone, then dremel and bondo to finish it up. Rondo is usually used if the 3d model was missing some parts.