The eternal problem of 3D printing is the size of your print bed. No matter how big it is, it’s never quite big enough for your dreams. But it’s okay: you can make up for your printer’s failings by learning to join the many pieces your printer’s spat out together.
First, let’s actually join your pieces together.
Start by roughing up the surfaces that you’re going to glue together, with either sand paper or a blade. This will give the glue a better surface to bond to, and make your join stronger.
For small props, and pieces that aren’t structurally important on larger pieces, these joins can be done with superglue (proper name: cyanoacrylate glue). Use this kind of glue sparingly, you want just enough to cover the surface you’re adhering with as little extra as possible. Any extra glue will make the seam take longer to cure – and you’ll have to clean it off after if (when) it leaks out the sides.
Remember, cyanoacrylate adheres to skin very quickly, so make sure you glove up for these seams! If you aren't sure what kind of glue to buy, head over to our basic supplies for bodyshopping page.
Another fun thing about cyanoacrylate is that you can purchase setting spray for it, which
instantly sets the glue. This is especially great for seams that are difficult to hold in place or are particularly delicate. If you can hold your seam with one hand, you can spray the outside of your seam – or, if you’ll need both hands to put your seam together, you can apply the glue to one side of the seam, and setting spray to the other. Do note, this will essentially dry your glue instantly on contact, so this might not be feasible for seams with more than one connecting plane, or if your hands are a bit shaky. (I, personally, the writer of this, suffer from the shaky hands problem).
Tip: If your pieces join together on a dowel or key and you're having trouble fitting it on, check our dowel and key troubleshoot guide! Always do a dry fit before applying glue!
But what about big seams on big props, and anything you’re really worried about breaking? For that, we bring out 5-min, 2-part Epoxy (or, Two part Gel Epoxy).
We also bring out the appropriate PPE at this stage, because we love our lungs in this house. So put on your masks, put on some gloves, open a window, and if you’re gonna be hovering in close put on some safety glasses/sunglasses as well to keep the fumes out of your eyes.
This is a two-part glue that comes in a two-part tube. You push the plunger down to dispense product, then mix it together yourself. Once you mix the epoxy together, you have a set amount of time before it begins to set and is no longer workable. This is usually somewhere around five minutes, but every tube is different, so make sure you double check every time so you’re not surprised in the middle of your seam!
Gel Epoxy is, like the name consists, a gel consistency, which can be scooped up with a popsicle stick (or similar implement) and applied to the surfaces to be stuck together. You’re aiming for a thin layer like jelly on a sandwich – but honestly, I prefer to over-apply and correct later on any seam I’m using epoxy on, because I want those seams to be as strong as possible.
Once your seams are together, the next step is to clean them up! Whatever glue you’ve used, any extra can be sanded away in exactly the same way a 3D print is bodyshopped. Start with 180, and work your way finer from there if you find you need it.
Once you’ve sanded that down, it’s time to look at your seam that you’ve made, and ask yourself a serious question: are there still gaps that need filling?
The answer is probably yes. I won’t say it’s always yes, because I’m sure that happens, but I personally can’t remember the last time it happened to me that something I put together didn’t need any additional filling.
You don’t need to break out the Epoxy again – even epoxy’d seams can be filled in with a mixture of superglue and baby powder. Yes, it’s essentially the sink repaired with ramen noodles and glue of the crafting world. What adding baby powder (either talc or cornstarch based) or, yes, finely ground ramen noodles does is thicken the glue, which both makes it easier to control, and also makes your glue go further.
So let’s make some glue gravy!
Tip: You can skip making the baby-powder and superglue mixture and fill gaps with spot filler if you have access to it! We recommend Acryl-Green, or Bondo. For this tutorial, we're going ahead with the powder, because everyone has their own, preferred methods! Experiment to see what works best for you and your projects.
We start by making a little volcano out of our baby powder. The basin in the middle is where I’m going to put one or two drops of super glue – just a tiny bit! Remember, super glue dries fast.
Using a popsicle stick, gently mix baby powder into the glue until you get a paste consistency, a little thicker than gel toothpaste. This is what you’re going to use to fill any gap in your seam.
I always over-fill the seams, paint it over each side, and then sand it down gently afterwards. Any extra glue is extra strength added to the seam, remember. It’s also entirely possible that your seam won’t be entirely level – it happens to the best of us. The extra glue can also help even that out.
Remember! Setting spray shocks cyanoacrylate dry instantly, and this works on the mix with baby powder as well.
Of course, this isn’t only good for gaps in seams, it’s good for gaps anywhere. Did your 3D printer mess up and leave holes in the print? Not a problem. Scratch your print while bodyshopping? Don’t sweat it. Drop your print and break it opening the door when bringing it back inside from priming? (Absolutely not speaking from experience on that one.) Any tiny bits that might have gone missing in the break, you can replace with your glue slurry!
Check your work on filling with another layer of primer...
This was close, but not quite! So I refined it once more, sanded it back to 320 grit, and did another layer of primer on this. Eventually, this was used as a mould, so it had to be virtually seamless for a tidy cast. Here’s the final sanding, as well as the seam area on the final product (poured in flexible rubber).
You may need to fill, sand, and prime several times in order to get your seam as invisible as possible, but stick with it! The final product looking seamless will be worth the struggle especially in the case of a Master, like this one, which can be used to make more than one final product.
