Ornaments From 3D Filament Scraps

I bought a 3D printer. I have been having a lot of fun learning how to use it. Even if all my prints were perfect (which they have not) I would still have filament scraps. My bucket of rafts, supports, and misprints is getting pretty full.

I tried melting some of them in the oven and the plastic melts pretty easily and pops out of silicon molds perfectly. My first try was in a metal pan lined with foil. Not so good. Most of the foil peels off OK but any little folds or crinkles may want to hold onto some of the plastic. If this is what you are going for, well, great. Not what I wanted. That is what lead to the silicon molds. A silicon mat works too.

• PLA filament scraps--other filaments melt at higher temperatures, and I don't recommend them
• Silicon molds or mat--most of the molds I have, I got from the cake decoration section of the local craft store. Their intended use was for anything from cupcakes to candy to ice cubes.
• Scissors, tin snips, the little cutter that came with the printer, a hammer--anything that will generate small pieces that will fit into the molds
• Safety glasses--for the cutting step
• Cookie sheet--stable platform for the silicon molds
• Wooden stick or pointy tool--explained later
• Oven
• Screw eyes or paper clips--for hangers
• Drill and drill bit of appropriate size for the screw eyes

SAFETY FIRST. Little bits of flying plastic can become dangerous projectiles when they fly too close to someone's eyes. Make sure that everyone nearby has eye protection. When you hear a piece hit your glasses you will appreciate the fact that you put them on.

Cut the scraps so that they will fit into the mold. I like to get a layer of tiny pieces at the bottom. It tends to help fill in the details of the mold without the annoying air bubbles. Then I fill in with whatever sizes fit in the mold cavities.

If you have large prints that are impossible to cut, look for the horizontal print lines. These are the weak points. I take little snips with the clippers that came with the printer. If you can snip in a bit, you may be able to separate the print into layers that cut more easily. If all else fails, try a hammer.

You can sort your scraps buy color at this point if you want.

I try to overfill each cavity because the level will go down as the plastic melts. With some molds--like the ice cube molds which are pretty deep--this is not a problem. I don't necessarily need the finished piece to be as tall as the cavity. With the tiny candy molds, I want the mold pretty full when this is all done.

Save the rest of the small scraps to keep adding during the baking process.

I always use a baking sheet under silicon molds since the molds are so flexible. I have an old one that is dedicated just for crafting. It does not need to be the beautiful shiny new one with the non-stick coating. Getting the molds in and out of the oven is the only function.

I set the oven to around 400 degrees F (which is close to 200 degrees C). Adjust as necessary. I have found that my air fryer oven can only handle the tiny candy molds. Silicon is a nice insulator so it may take a while for the heat to make its way to the bottom of the large cavities. The top will melt before the bottom even gets soft.

If you are using molds of several sizes, you can take the tray out of the oven to check them (and poke around the larger pieces to check on their progress. It will not bother the melting process to start and stop the melting--it just delays it a tiny, un-noticeable amount. (Patience is required at this point but 3D printing requires a bit of patience.) Remove the smaller molds when they are done and return the large ones to the oven.

Any melted plastic that is on the lip of the mold should be poked into the melted part at this point. This is where your pointy stick or tool comes in. I have tried a wooden stick and it does work but sometimes liquid plastic sticks really well to the wood. The metal tool from a knitting loom is my preferred tool. Just don't use plastic tools. Depending on their melting point, you may find that they have become a part of the project.

If you like the uneven bottom edge of your piece, don't poke all the stray bits in. But remember if plastic is extending over to the flat part at the top of the cavity, it will solidify there and be hard to deal with later.

Add more plastic if you want the pieces thicker. Any misprints that originally had a lot of infill gaps will sink quite a bit while in the oven. I poke the air bubbles on the surface with my tool. If they are not dealt with now, they will be there for good.

When the pieces are the way you want them, let them cool to room temperature on the baking sheet. Do not try to unmold them just because the top feels hard. The center may still be liquid.

I wanted my trees (the cone mold) to have tree trunks. I did not have scraps of PETG or TPU (higher melting points) handy, so I used small chunks of pencils. An old screw would look cute too. Do this when they first come out of the oven. I baby sit mine for a few minutes until the melted PLA is hard enough to support them. I don't want the trunks to slide too far sideways.

You can pile up scraps on a silicon mat (which should be on the baking sheet--obviously!) The pile will flatten out quite a bit in the oven. You will leave it in the oven long enough to fuse the pieces together.

You can use larger pieces of misprints and try for the melting snow effect.

I forgot to take a before picture. Sorry. Baking flattens everything more than you would think.

I usually use my Dremel for this. If the plastic is too hard, you can warm it with a heat gun (set on the low side) or a hair dryer (set to high).

When using the mat instead of a mold, you can place a paper clip (or at least part of one) under your pile of plastic. I like to wait until it is partially melted to do this. That way I know which side I want to point up. Without the sides of the mold holding the heat in, I usually only have to wait a minute or 2 before I can bend the plastic up just enough to get the paperclip in. Pop the tray back in the oven to finish.

Add a drop of super glue to keep the hanger in place after everything has cooled if necessary.