Vacuum forming clear Styrene?

[craigolio1]

Hello all.

I have some Shapeways Rocky Mountaineer Ultradome cars.  They were printed in white strong flexible plastic which is brutal.  They have solid windows and have required a need a huge amount of finish work to make them even half way usable models. I could pay alot more money and order them in FUD but the windows will still be printed.  Even then they'll be substandard as I'll be painting the windows black and it won't look right.  I'm going to finish at least one but my mind is moving onto scratch building one for the Rocky Mountaineer, and the three cars that I need for my BC Rail Northwind.

I was thinking of Vacuum forming a clear styrene window section which would basically form the body structure, and then doing a wrap of .005" styrene, or maybe even etching a wrap, for the body.  I've never done any vacuum forming but I have read about making a table using my shop vac and it seems pretty straight forward.  My question is about the clear styrene.  Can anyone offer any insight into how it will perform when heated and ultimately stretched over a form? Will there be any colour changes or distortion?  Any other caveats I'm not considering?

Thanks,

Craig

[C855B]

YMMV with a modern setup, but a gazillion years ago I tried forming clear styrene on a real, honest to gosh Mattel Vac-U-Form (!!!). Anything resembling a corner turned white, and curved areas came out cloudy. Commercial vacuum-formed clears - R/C car bodies and R/C aircraft canopies, for instance - are some manner of polycarbonate, I think.

@peteski is likely to know more about this.

[craigolio1]

thanks for the input. 

My set up will only be modern in sense that I will have made it my self in modern times.  I figured there might be some issue. 

The cars on the prototype have a pretty dark window tint, but clearly see through in photos taken in the right light or from the right angle.  I wonder if the discolouration would be less noticeable with a coat of a smoky clear paint?

It would probaly still look beter than painted black windows on printed model with lines in the printed windows.

Craig

[Spades]

Posted this before, on my to do list.

[nscaler711]

You could try lexan. That what is used for hobby grade RC vehicles like Traxxas, Losi, Vaterra, HPI, etc.
Its pretty sturdy and flexible; though it is a little thick...
You can buy sheets of it for vacuum forming though but it wont do n scale sized details...

[craigolio1]

Sweet video. Exactly the sort of thing I was planning.

Lexan is a good idea. I don't need any detail. Just a fairly rigid car body shaped clear piece of plastic. I'd be building a car body on the out side of it.

Craig

[nscaler711]

If you space enough out you could probably get a bunch done then just in case you want more or if the screw up. But it's great for bashing around a bit, luckily you won't be bashing trains together... Hopefully.... 

[peteski]

Best clear materials for vacuu-forming are Vivak (PETG) or Lexan (polycarbonate). PETG is what is used for all the blister packs used for packaging consumer products.

[craigolio1]

Peteski it's interesting that you mention blister packs.  I looked around at the prices of Lexan and it's not cheap.  I couldn't find any suppliers close to me here in the great white north.  Ebay and Amazon.com seemed to be the best options.

I then had the idea to experiment with some recycled blister packs.  Certainly when heated they could be reformed around my simple mold.  Worth experimenting with anyway.  No to keep my eye out for usable pieces.

Craig

[peteski]

Peteski it's interesting that you mention blister packs.  I looked around at the prices of Lexan and it's not cheap.  I couldn't find any suppliers close to me here in the great white north.  Ebay and Amazon.com seemed to be the best options.

I then had the idea to experiment with some recycled blister packs.  Certainly when heated they could be reformed around my simple mold.  Worth experimenting with anyway.  No to keep my eye out for usable pieces.

Craig

Funny that you mentioned the cost. That is exactly what is mentioned on http://www.plasticsintl.com/petg.htm

You can readily get 0.020 PETG on eBay and Amazon (in small or large quantities).  But I still have not been able to locate a source of 0.015" and 0.010" Vivak in the size that I need.  K&S Metals (the brass tubing people) sell those thicknesses but they are too small for my needs (I need larger than 8.5" x 11").  Micro-Mark carries the K&S Vivak sheets.

I suppose you could try to re-use some blister pack material but the thickens of it might already not be even due to it being already formed.

[narrowminded]

In gearing up my home shop I have purchased one like this.  It is a dental former and works good.  A similar if not the same unit was/ is sold by Micro-Mark.  The material blank window is not large (roughly 5" x 5") so it's not suited to big things.  I would consider it for what you're trying to do.  You can also make frames to hold smaller material blanks if you're doing smaller parts and don't want to waste material.

http://www.ebay.com/itm/Dental-Lab-Vacuum-Forming-Molding-Machine-Former-Heat-Thermoforming-Equipment-/291786277611?hash=item43efd142eb

One problem with vacuum cleaner units is not having enough vacuum.  For larger sheets with relatively shallow features it may work but then again, you may accomplish that by just heating the material in the oven (to about 275 F).  Place on a flat piece of plywood with a cloth/ linen barrier also folded over the material to help maintain heat and so you have a way to handle it when you pull it out of the oven.  Have your mold ready and use a piece of foam (pillow?) as your pressing tool.  Slide the heated piece off the board and on to the mold and then press down with your foam former.  I've also done two part molds from wood to make shaped fenders in some models built and made motorcycle sidecar windscreens this way.  For the motorcycle screens I just laid the heated 1/8" or 3/16" material over the nose of the sidecar that wound up having the right contour for the finished screen and gently pressed the uniformly heated acrylic sheet  with a bath towel used as the wrap for insulation while running from the kitchen to the shop as well as handling while transferring and laying in place.  It was an oversized rectangle that was then finish trimmed (grinder) once formed.  They were quite perfect, not just OK.  It works. 

Try playing with some material that's been uniformly heated in the oven.  You might surprise yourself what can be done that way.  For detail you'll need vacuum and a pretty powerful one at that.

[robert3985]

Here's a technique that might work for you, at much less cost than building a vacuum forming setup.  Evidently, it's pretty well known and used to form model canopies.

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It's not English, but it's pretty self-explanatory and there are other youtube videos available for other similar projects.

Additionally, depending on the tint of the windows on the prototype, you might be able to come pretty close using a soda bottle that's tinted...

Cheerio!
Bob Gilmore

[craigolio1]

Wow!!!!!  Game on.

[narrowminded]

That's pretty cool how that bottle contracts appropriately with no outside force.  That's also worth remembering when using vacuum form or blow molded parts, anything that reshaped heated plastic, that it has some residual stresses that want to go back in the direction of its original form when it gets warm enough.  Also why scraps from blister packs might be suitable as a raw material if it suits the needed size.  Segments cut out of plastic bottles might also work.  I'll be trying some of those things as the need for an odd piece arises.

[craigolio1]

Good call.

I think the force is provided by the handle and the wedge.  It looks like it's stretching the bottle into and oval shape and then the plastic is also shrinking.

So a quick search for grey tinted soda bottle came up empty.  Makes sense.  Grey soda doesn't look delicious, and no one drinks grey water... or boy I sure hope they don't.  Tamiya doesn't make a smokey grey clear.  To tint the windows can I just add some black to some clear coat and airbrush the inside, after forming?

Perhaps shoot just clear on the inside, and then a mixture onto that so it has a good surface to bond to making a more uniform tint?

Craig