Found a nice site for instructions and for supplies.
I doubt very much the OP wants to play with molten anything when two-part resins are an option.
Hey, Chronos - I bet your pass would look great done as acold casting, say in a nice bronze.
Bronze or any other metal is Right Out, for two reasons. One, I wear this thing on my belt, and metal would be way too heavy. Two, I know that there are some students for whom anything like this, if made of metal, would be instantly weaponized.
And I really wish that I could examine some of these materials in person, to poke them, feel their heft, and so on. It’s hard to tell what I want just from pictures.
Cold casting isn’t metal, it’s resin with a dusting of metal powder put on the mold beforehand, so the surface is metallized (OK, you can, and usually do, also put metal powder in the resin, but that’s not necessary for the effect) - it doesn’t weigh that much more if it’s just on the surface, and certainly isn’t any more weaponizeable…
Ah, OK, then, I just learned something. While there are some other projects I have that I’ll definitely keep that in mind for (in fact, there’s a particular project where I think that’ll make things a lot easier for me, and for which I though I was going to have to learn metalworking), for this, I’m aiming more for a day-glow green (I want it to be highly visible, and that’s the color of the existing belt clip).
I’m no expert on 3-D printing materials, but is printing it (yourself or outsourced) in a softer, slightly more flexible, type of plastic an option? It would abrade more, but resist chipping better.
The materials I’ve been mentioning are for making the molds–none are suitable for the final product. All the molding materials are easy to tear and very rubbery and the resin is brittle and tends to remain tacky on the surface (a hall pass made from the resin I linked wouldn’t just chip if dropped, it would shatter.) That’s why I mentioned temperature of the melted plastic, I don’t know what type of plastic or composite would be closest to your necessary traits and easy to work with. IMHO the milliput (linked previously) would be the closest material to meeting your needs. A cheaper option would be some flexible Sculpey (available on-line, in craft shops, in toy stores, even at Wal-Mart.) I personally don’t think you are going to find an ideal plastic that fits all you needs that doesn’t need to be a liquid pour.
Here is the (not very detailed) official page for a type flexible Sculpey. You could probably mix green with yellow to get a suitably noticeable color. (If not, you could paint it.)
I’m a lot more worried about the material for the finished object, not for the mold. Would Sculpey stand up to repeated handling? I’ve only seen it used for display pieces.
Meanwhile, I stopped by Pat Catan’s today to see what they have, and noticed two things:
1: Two-part epoxies are very expensive. Even for the hard ones that I don’t think would be suitable, I’d have to pay at least $13, and for the more flexible ones, it looks like the smallest purchase would be close to $50. For that price, I could just print a new hall pass every semester for a decade.
2: Right next to the epoxies, they had a supply of an inexpensive rubbery material which is easy to melt and which holds together when it solidifies. I know it’s a crazy idea, but what do people think of making an object entirely out of hot glue? It is, at least, something that I already have easy access to, so I can do some experiments with it without having to invest much.
EDIT:
Well, a liquid pour was what I was thinking of in the first place, anyway.
Yes, it should be fine. The display pieces you’ve seen probably have been elaborate objects with lots of fine details. And are likely made with the standard, non-flexable Sculpey. Your pass passes for a barely shaped brick. Should be pretty stout. (One common use for Sculpey is for bead making, so it is durable enough for that.)
That actually sounds like an excellent idea. Glue sticks seem pretty durable, and (ironically enough) aren’t sticky when they harden, unlike the resin I’ve mentioned.
(And it actually makes me want to do something with some of my glue sticks–I was once working somewhere that was having a sort of “spring cleaning”, and one thing I was supposed to throw in the dumpster was a box of glue sticks. And I don’t mean a little packet like you buy in a craft shop, I’m talking something like 30 pounds of them. So of course I kept them. But they are a different diameter than what are used in consumer glue guns, so the box has been tucked away under a bed for around 15 years. Only time I’ve used one to seal something, I cut a soft drink can in two, chopped up a glue stick, and melted it in the can.)
By “liquid pour”, I mean “several hundred degrees liquid pour.”
Which some of the proposed mold materials can handle just fine (though it’s certainly incompatible with the idea of a 3d printed PLA mold).
And in addition to the standard guns, the hot-glue section at Pat Catan’s also included a few hot glue tubs, which I presume one is meant to apply with wooden sticks or the like. You could use one of those with your off-size glue sticks. Or just get an appropriately-sized gun, I suppose.
I don’t remember the exact temperature tolerance of the materials I used–the hottest thing I poured into them is this (which wouldn’t meet you needs even if you hadn’t said “no metal”, because not only is it brittle, it contains lead.)
Well, I opened the thread talking about plaster, which can handle almost any temperatures, and some of the silicones I saw on some of those pages said they could do bronze.
Anyway, I think my current plan (pending the results of some tests) is to print the mold, and then fill it with hot glue, probably using talc as a mold release. I think I can keep the mold from melting; I might leave it in the freezer a bit before the fill.
Use Silicone spray as a mold release.
Unless you use “cool melt” glue, you are going to melt your mold. The material used in 3-d printers is basically hot glue.
There is also the possibility of using plastics that aren’t completely melted but made just soft enough to droop into the mold. I’ve never tried vacuum forming before, but I’m familiar with it from reading (just from curiosity) a “how to” site on making your own storm trooper armor. Take a look at this.
It crossed my mind that PVC would be an excellent plastic to use. It seems to be workable. You could make a two-plaster mold from a print of the pass, put suitable pieces of PVC in the two halves of the mold (separately) and gently heat it in your oven until it softens. Either glue the halves together later or make sure the surfaces are flat and (carefully) heat one of them with a blowtorch or bunsen or fisher burner, then press the two halves together. You could also possibly use old records.
You can read about our own Mangetout’s adventures in molding recycled plastic on his (excellent) blog. Maybe PM him?
I meant a “two-part” plaster mold, in case it the meaning isn’t clear through the malaprop.
The first experiments with hot glue are a success. I took a 3D printed part that didn’t turn out right, and tried making a hot glue imprint of it. On the first try, I forgot to use a mold release, and so the glue stuck permanently, and while it didn’t melt the PLA, it did seem to warp it a bit. For the second try (on a different part of the piece), though, I pre-froze the mold, and used cooking spray as a release, and it worked fine. There were a couple of voids, but other than that, it came off easily, and picked up finer detail than what’s on my pass, without damaging the mold.
I think that for the pass mold (which will need a larger quantity of filling, and hence more total heat), I’m going to sand away the outer surfaces of the 3D print to expose the internal honeycombing, fill that with water, and then freeze it before use. That should be more than enough to prevent melting of the mold.
My uncle also suggested using silicone caulking as a casting material. It should be extremely easy to work with (low cost, no heat, only a single material needed), but the downside is it takes a very long time to cure (perhaps as much as a month, he estimates). So I’m going to try the hot-glue method first.
Oh, I love that stuff! (I use the variant that comes in strips of blue and yellow, which you knead till it’s a uniform green.) I’m told that the sculptors of old D&D 25mm miniatures used it for their originals, to make molds to use for poured pewter/lead/lead-tin/whatever. It’s also aces for home repair!
What CAD language do 3D printers use, anyway? How hard is it to learn to program in it, to design your own stuff?