recycling plastic trees

[Artic Fox]

Hi, I was wondering if it would be possible to melt down the plastic trees, the ones that hold the model pieces, so that I could use it for parts casting instead of resin.

[Marc]

Two words: Toxic Fumes!
 
I don't think that's a very good idea. There are other better solutions for casting and the recycling thing is kinda loss in the melting process due to the toxicity of the thing.

[Artic Fox]

aw dang,  stupid toxic fumes, oh well. Thanks

[Major Blah]

Ezechiel is right, it's not  a good idea.

The most useful thing I saw coming from those sprue is a Borg Cube  

[fulcy]

Actually, you can use the sprue for some things - if you take a straight piece of sprue, grab one end with one hand, the other with the other hand, and hold it over a candle, and then pull very slowly, you'll get very very thin bits of plastic - which have been used for wires, antenna, and rigging on aircraft and boats...

[Artic Fox]

Thanks fulcy, just wish I could use the sprues for parts casting, becuse I have so much, I bought 6 master grades att the anime expo

[fulcy]

The only real way you'd be able to use them for parts casting is if you had an injection molding machine - which i am guessing you don't .  You can melt the plastic relatively easily, but there are two problems with trying to using the resulting liquid in a mold:

First off, the melting point of the plastic is going to be very high - couple hundred degrees I would guess - and I am going to go out on a limb, and say that those temperatures aren't going to be good for your silicone mold.

Second, the liquid plastic isn't going to be thing like the two part resins we use for casting - hence the use of these plastics in injection molding machines, which inject the heated plastic into the mold at high pressures.  As the plastic goes into the mold, especially through thin sections, it cools down dramatically, and unless you are using an injection molding machine, you won't physically be able to get the liquid plastic into the mold before it cools too much, ruining your pour...

[fredpekker]

The most useful thing I saw coming from those sprue is a Borg Cube

It just so happens that I have a box of sprues for just that purpose.  

[Asmodeous]

There is a way to reuse your sprues.  It's not a casting process or anything but it's helpful at times.  Take a file, knife, cutters, pencil sharperner, whatever is easiest and cut, file, whittle, whatever.. small particles of the sprue.  Gather all of this in a dish preferably glass and add plastic cement.  It will melt the plastic makeing a nice easy to use putty.  I've used this a few times to fill a mistake area or wide seam.  Works decently enough.   Fumes aren't too terrible as they are no more than normal welding of seams.

[mrmaigo]

There is a way to reuse your sprues.  It's not a casting process or anything but it's helpful at times.  Take a file, knife, cutters, pencil sharperner, whatever is easiest and cut, file, whittle, whatever.. small particles of the sprue.  Gather all of this in a dish preferably glass and add plastic cement.  It will melt the plastic makeing a nice easy to use putty.  I've used this a few times to fill a mistake area or wide seam.  Works decently enough.   Fumes aren't too terrible as they are no more than normal welding of seams.

Okay, so where do you get cement cheep?

[pu_rplecow]

Ha, i've actually tried to cast a part from this and using clay as a mould. Didn't turn out so good but what i did wasn't to melt the plastic, i used industrial thinner to dissolve the sprues. It took days, some warming of the gooey mess in a test tube to evaporate the excess thinner to thicken the mixture and after application, ages to dry out. Shrinkage is terrible as well - probably cos i had the mixture too thin. But i'm sure it'll work!   Get a can of industrial strength thinner, i wouldn't use normal cement to make this stuff. I suspect normal cement might even just be industrial strength thinner with abit more QC packaged into tiny bottles and prices jacked up.

[Major Blah]

I think the conclusion we can draw is that casting with sprue is not worth the time and health hazard.

Time is money, not to mention health.  If you want high quality cast just go for resin.  There is a reason why people use resin.  I think plastic molding is a profession (die making as well), so you need specialized equipment and knowledge for this sort of stuff.  Actually, I think it's kinda fun to design molds, must be a lot of tricks/techniques, and CAD/software required.

[fulcy]

I think the conclusion we can draw is that casting with sprue is not worth the time and health hazard.

Time is money, not to mention health.  If you want high quality cast just go for resin.  There is a reason why people use resin.  I think plastic molding is a profession (die making as well), so you need specialized equipment and knowledge for this sort of stuff.  Actually, I think it's kinda fun to design molds, must be a lot of tricks/techniques, and CAD/software required.

Yes, I can say from experience (not only silicone molds, but injection mold designing), that mold designing is kinda fun...