has anyone ever done this

[rdgracer71]

ever heard of anyone melting plastic model parts to use to make your own parts....what i mean is taking model pieces maybe a body or other things and melting them in a can or pot and pouring it into a mold to make parts with....would this work....you know once it cools it will become hard again.....just asking....

[DrewCfromSC]

Goor question, other than as a kid setting models on fire I dont have an answer. Im guessing it wont work due to the structure of plastics in general. Hope someone with more knowhow answers you.

Drew "Shootenanny" in S.C.

[Tradeshowjoe]

I don't know about actualy "reusing" styrene. I have "stretched" my sprue (LMAO) for wire and antennaes, holding old sprue strips over a candle flame.

If you need a custom part, try resin casting. I recently started doing it, and it is easy. I use "Amazing Casting Resin" easy to find and use.

Edited July 9, 2010 by Tradeshowjoe

[crazyjim]

Never heard of recycling styrene cars. Wouldn't it be a smelly process? I'd like to try casting some of my own parts but would need to see a tutorial here first.

[David G.]

I think the styrene is too thick to properly flow into a mold under gravity pressure alone. That's why the kits we buy are "injection molded." The plastic is forced into the molds under pressure. Resin on the other hand can range from water-thin to almost as thick as silly putty depending on it's intended use.

What you suggest is an interesting thought, but if it was something that was easy or practical, I think there would be a lot of people doing that instead of casting in resin.

If you do try melting and recasting styrene, be careful. It burns readily, gives off really nasty, toxic smoke and fumes and when it burns, it turns into a flaming liquid that can be difficult to keep under control.

[Eric Stone]

I wouldn't try it... The styrene will put some nasty stuff into the air that you'd be better off not breathing.

[LDO]

I read about it maybe 25 years ago. The idea was to chop up sprue into tiny pieces and melt them, them pour into an open mold for something like an aircraft canopy. That would leave you with a part that's only suitable for use as a vacu-form master. I tried it once with poor results, but I was only 15 or so. It makes no sense today, with casting supplies so readily available. Really it made no sense 25 years ago, with the availability of polyester resin (fiberglass).

I used fiberglass to make a mold and a copy of this scatchbuilt scoop in 1/8 scale.

[torinobradley]

There are small, table-top plastic injection molders available but they use a press type mechanism to create the injection part of the process. Also, because of pressure needed, RTV molds may not stand up to the casting process. Here's a link to em.

http://www.injectionmolder.net/

Other than this type of mechanism, I don't think you'd have much success due to viscosity issues.

[Danno]

You can cast small parts with styrene and an open mold, but rather than melting the styrene with heat, dissolve it in liquid cement (Tenax, Ambroid, etc.). And, you can use it as filler material instead of body putty, etc.

The method is to chop up styrene into small pieces (such as cutting-scraps or chunks of sprue), then add the liquid cement to dissolve the pieces into a pourable semi-liquid; pour into the mold and let it set; allow sufficient time for evaporation and you'll have a cast styrene part. Just like resin casting, but different material.

I keep a little of the dissolved styrene on hand in an old glass liquid cement jar (just keep it tightly sealed). If it gets too thick, just add a little more liquid cement.

[AzTom]

There are small, table-top plastic injection molders available but they use a press type mechanism to create the injection part of the process. Also, because of pressure needed, RTV molds may not stand up to the casting process. Here's a link to em.

http://www.injectionmolder.net/

Other than this type of mechanism, I don't think you'd have much success due to viscosity issues.

Thanks for that link. I have two of those table top injection machines. I may have to dig them out and do some playing.

AzTom

[GrandpaMcGurk]

Thanks for that link. I have two of those table top injection machines. I may have to dig them out and do some playing.

AzTom

Tom, this unit has me intrigued....if you have a couple I'd be very interested in knowing more and what you think of the results you get.......please and thank you.

Edited July 10, 2010 by GrandpaMcGurk

[Mark Brown]

You can cast small parts with styrene and an open mold, but rather than melting the styrene with heat, dissolve it in liquid cement (Tenax, Ambroid, etc.). And, you can use it as filler material instead of body putty, etc.

The method is to chop up styrene into small pieces (such as cutting-scraps or chunks of sprue), then add the liquid cement to dissolve the pieces into a pourable semi-liquid; pour into the mold and let it set; allow sufficient time for evaporation and you'll have a cast styrene part. Just like resin casting, but different material.

I keep a little of the dissolved styrene on hand in an old glass liquid cement jar (just keep it tightly sealed). If it gets too thick, just add a little more liquid cement.

I've been using this technique instead of typical filler for some time. I generally use stretched sprue and Ambroid and I've found few situations where this wouldn't work. I just put pieces of the stretched sprue into the area to be filled and dab it with Ambroid until it softens enough for me to work it with a toothpick. Once it gasses out and hardens, it sands exactly like the surrounding plastic and it won't be affected if you have to strip paint from the part(s), as typically happens with most fillers.

[garagepunk66]

You can cast small parts with styrene and an open mold, but rather than melting the styrene with heat, dissolve it in liquid cement (Tenax, Ambroid, etc.). And, you can use it as filler material instead of body putty, etc.

 

The method is to chop up styrene into small pieces (such as cutting-scraps or chunks of sprue), then add the liquid cement to dissolve the pieces into a pourable semi-liquid; pour into the mold and let it set; allow sufficient time for evaporation and you'll have a cast styrene part. Just like resin casting, but different material.

 

I keep a little of the dissolved styrene on hand in an old glass liquid cement jar (just keep it tightly sealed). If it gets too thick, just add a little more liquid cement.

Sorry to dredge this old thread up from the dead; but I am also contemplating the open-mold concept of casting a styrene/Tenax mixture. I also use this combo instead of filling with putty so I'm quite comfortable with it's working characteristics. Using SCI-Grip 3 intsead of Tenax  (covered in other threads on this forum - available from Amazon http://www.amazon.com/gp/product/B00466V8F0?psc=1&redirect=true&ref_=ox_sc_act_title_3&smid=ATVPDKIKX0DER ) would make it more cost-effective too, and lord knows i have enough sprue to melt down. I have an original AMT 69 Falcon Kit and i want to make molds of the wheel opening areas, the trunk-lid section between the tail-lamps and window frame detail to cast sections for adding back to the current-release modified-stocker body and I prefer to work in all-styrene. I would think that a very-thin mixture that would be brushed in and built up in subsequent thin layers would work pretty well if allowed to dry thoroughly between coats; and the subsequent coats would fully fuse with what is already cured out.      

[Ace-Garageguy]

I hate to be a bubble-burster and bring in some reality, but unless you cast VERY small or thin parts, you're going to have a SEVERE problem with shrinkage and warping due to the evaporation of your solvent.

The big REASON that 2-part, catalyzed products (like polyester, urethane, silicone, etc.) work well for casting and for molds is because their chemistry allows them to harden without significant evaporation. They contain very small amounts of solvents that evaporate out, and because of this, they shrink and deform much less than things that have to "dry" to harden up.

Sure, you can probably use a styrene / solvent mixture, brushed on in thin coats, allowing it to dry between coats. This is EXACTLY the method you use if you make molds from plaster, latex, or other materials that have to harden by evaporation.

But why bother reinventing the wheel, when cheap, effective products already exist to do professional-quality work every time?

Some other questions arise too, like what you plan to use for a mold-release agent if you're making your molds ON STYRENE PARTS by using a material that includes solvent that attacks and melts STYRENE PARTS.

Many things are possible that aren't particularly good ideas, or that have severe practical limitations, and this is one of them.

On the other hand, bits of styrene dissolved in liquid 'cement' can work well as a filler.

I've done a fair bit of hands-on research into the various ways of copying parts in scale as well as in 1:1 over the last 40 years, and I've found that using catalyzed products that cure by polymerization is far, far better than materials that have to "dry".

Here's a thread I posted years ago that shows how to make molds that actually work, and how to produce STRONG parts that are close to scale-thickness. 

http://cs.scaleautomag.com/sca/modeling_subjects/f/30/t/97991.aspx

 

 

 

Edited February 23, 2016 by Ace-Garageguy

[Mark]

There are small, table-top plastic injection molders available but they use a press type mechanism to create the injection part of the process. Also, because of pressure needed, RTV molds may not stand up to the casting process. Here's a link to em.

http://www.injectionmolder.net/

Other than this type of mechanism, I don't think you'd have much success due to viscosity issues.

I've got a book that describes how to build a machine that looks a lot like that one.  I bought the book more to see what was involved, as opposed to actually building the thing. 

Mattel used to make an injection molding machine.  Theirs used plastic with a lower melt point, the plastic felt like a cross between greasy soft toy plastic and glue sticks.  The thing didn't get hot enough to melt anything else.  As I remember, the molds were pretty small.  The Thingmaker operated on a similar principle, but the soft material for that probably had a low melting point.  I remember the molds for that being pretty decent size-wise, producing much larger "things" than the injection molder could churn out.  That Thingmaker goop was nasty stuff, when it was hot it would stick to you like mad.

The limiting factor will be tooling.  You can get RTV material that is usable for casting metal items, but you'd need something that could handle the pressure of injection molding, and RTV ain't it.  Metal tooling isn't cheap.  I inquired about having a tool cut for a 1/25 scale hood about thirty years ago; I was quoted in the $5,000 range for an aluminum tool.  And that's a hood...shape would be critical but there's no really intricate detail.  Then you'd have to find someone to run it.  There are some industrial epoxies that might work, but that would be an expensive way to go.  I can't see any advantage to home-brew injection molding over decent quality resin castings, especially with the cost/difficulty involved in the former.