This is the first part of our ongoing series on finishing 3D prints, which we hope will be a beginner friendly, there-are-no-stupid-questions take on finishing 3D prints. This guide is a great follow-along if you've purchased any Dangerous Ladies 3D printed cosplay props. This article is on the basic supplies you'll need for sanding FDM prints, with no frills or anything fancy, sticking strictly to what gets the job done. We'll have articles on optional tools and supplies for more complicated finishing jobs in the future.
If you already know what to do and just need a shopping list, click here to jump forward!
Using the methods in this tutorial, we turned the Riddle Roseheart's cane into a finished prop!
Preparing a 3D Print for PaintingWe call the process of surface-finishing a 3D print "bodyshopping". Bodyshopping (or body work) is a term usually used to describe the process of fixing surface issues and damage to cars. Here, we're using it as an all-encompassing term to describe the process of turning a fresh-off-the-printer 3D print into a smooth, ready to paint thing.
How much bodyshopping do I have to do on my 3D print?
Only as much as you want. There are no rules about aesthetics in cosplay, so if you want to just slap a print together and go, you can do that! Nothing here is mandatory, it's just a "best results" suggestion for people looking for a particular or more polished finish. For most projects, just a couple hours of bodyshopping can drastically improve your results. If a super polished look is your goal, the amount of time you’ll need to spend will vary on the size and detail-level and quality of your 3D print, the amount of time you’re willing to put in, and how detail-oriented you are about little things that people will only see if they’re pressing their nose against it.
What does bodyshopping do to a 3D print?
It does a lot of things! Including:
- sanding down surface imperfections
- joining pieces and filling in the seams
- replacing missing parts (ie, your printer failed to print a detail, so you sculpt in a replacement)
- create surfaces smooth enough to help shiny paints look as shiny as they’re meant to be.
- We’ll go into more detail on the various stages and processes of bodyshopping in a future blog post, but for now, we want to familiarize you with the materials involved. So let's jump right in to that!
Before finishing your 3D Printed Cosplay prop, you'll need...
... A place to do it in.Ideally, anywhere you can get messy! While 3D printing is generally pretty friendly to most spaces, sanding the prints smooth can get a bit dusty.
You'll want to consider the following in choosing a place to work:
- ventilation; backyards, porches and balconies are ideal for this
- ease of clean-up; spaces where you can get messy, like a garage or a workshop
- distance from food; you don't want to do this anywhere you eat, like a kitchen counter or your dining table
- access to a faucet; you'll want to refresh your water!
... Basic protective equipment (PPE).
NIOSH-approved masks and safety goggles should be considered when bodyshopping 3D PrintsPersonal protective equipment (PPE) is a must-have for any sort of crafting, but for sanding 3D Prints ("bodyshopping") specifically, you'll likely want your kit to have the following protective equipment:
- Some sort of apron to protect your clothes from sanding crud.
- A dust mask for large particles.
- A NIOSH approved face mask (with rubber seal with good fit to face) for organic vapors when spraying spray paints or using fillers
- Safety glasses when removing supports, in case any pieces go flying at your eyes.
As always with PPE, this is the best case scenario for you and your health. It won't kill you if you don't use these things, but you don't really know what kind of sensitivities you might have until you're deep into them. What you use is your choice, but safe is better than sorry.
...Sandpaper in various grits.Sandpaper is the best way to make a 3D print smooth and ready to paint. It is a gritty paper used to smooth down surfaces by gradually grinding away at it. The grits indicate how rough or fine the sandpaper is. A low number like 150 is very rough and a high number like 3000 is very smooth. You want to start with a low number to take off the worst of the print texture, and gradually move to a higher number so the surface gets finer and finer.
For the vast majority of use cases, we recommend having 150, 220, 320, 400 and 600, but you can make do with 150, 320 and 400. If you can’t find these specific numbers, just look for numbers in the same ballpark.
Going past 600 is mostly overkill; you only need to go into that territory if you are trying to get a mirror surface, and it is very hard to paint anything that smooth and shiny because many paints won't stick to it.
If you're sanding a resin print, it's very likely that you can start at 320 grit, as the print lines on resin prints are much smaller and resin is much softer, so it doesn't need rough sandpaper.
...A Bucket full of water.Sanding can get dusty, so we recommend wet sanding to cut down on dust and extend the life of your sandpaper. This is just a container with water and a bit of dish soap, used to wet the print and the sandpaper to keep things. The dish soap helps keep the sanding crud from sticking to the sandpaper. There's no recipe to this, just dollop some in and go.
Something as small as a plastic takeout container works if you just want something to wet and rinse your sandpaper in, but a wash tub or bucket is good if you want to be able to rinse your piece easily. The wash tub is also ideal if you don't have a laundry or shop sink because then you won't be washing sanding crud down the drain. If you don't have a laundry or shop sink, empty it into the storm drain outside! It won't hurt your plumbing if you have to put it down the toilet, but you should avoid putting it down your kitchen or bathroom sinks or anywhere you put food or clean your own body.
The exact temperature of the water doesn't really matter; warm is more comfortable, but cold is just as fine. We don't recommend very hot water because the heat can be damaging to 3D prints.
You should change the water every time you change sandpaper grits. If you're sanding with 400 grit and you've got particles of 150 left over, you'll just be scratching up the print you've worked so hard to smooth!
(Bonus supply: hand lotion. If you've got some long sanding sessions ahead of you, it can be very drying on your hands! Just about anything will do, but we like CeraVe's Reparative Hand Cream, Glysomed's Hand Cream, and O'Keefe's Working Hands cream.)
...A Craft Knife.
- to trim down parts of prints. This can be handy in removing excess support material, cutting off weird filament mistakes, trimming the bases of prints, and other small tasks.
- to apply body or spot filler. While you can use something like a popsicle stick instead, the finer the edge, the more precisely you can apply filler. We like to keep dull blades that are no longer good for cutting as blades to apply filler, as it extends their usefulness. You can also use a second blade to scrape any hardened filler off the first blade, making it reusable, unlike popsicle sticks or most other tools.
Our craft knife recommendations for finishing 3D Prints:
- Whatever's at the dollar store. You can buy replacement blades so the same housing can last you forever. Many craft knives come with a spare blade hidden inside the handle, but a pack of replacement blades is handy to have on hand and will last a long time.
...A Glue that can be Sanded.
If your 3D printed project is more than one piece, you'll need to glue the pieces together. What kind of glue you use will change depending on what pieces you're gluing together, but you'll definitely want this glue to be sandable so that you can smooth it out with sandpaper, the same as your other pieces.
2-Part 5-min Epoxy will be your go-to glue for assembling large 3D Prints
For assembling pieces that will have visible seams, such as two segments of a blade that should look like one whole blade, you'll want to use a glue with gap-filling properties. The high volume of the glue will not only hold the two pieces together but also fill any remaining space, helping fill in the resulting seam. A little bit of extra seeping out of the sides is good in these cases –– you can just sand it down! For this, we recommend a two-part, five-minute epoxy. Two-part 5-min epoxy generally comes in dual plunger tubes where you squish your desired amount out onto a tray, mix it, and then apply as desired. Mixing it up is
a little bit of work, but it's a great glue and it has just enough working time to let you assemble some pieces while not taking forever to cure, so you can keep going sooner. Virtually all five-minute epoxies are the same; we just use a dollar store brand called Adhaero because it's inexpensive and functionally identical to pricier brands like Gorilla Glue.
For assembling pieces that just slot into each other without a seam, such as gluing a little detail piece into its slot, we like to use superglue. Superglue is good for attaching small pieces because it is low profile, so pieces being attached won't bulge or stick out.
Our brand recommendations for sandable glue:
- BSI (Bob Smith Industries) superglue; it comes in different formulas for thickness; the purple bottle (regular) and pink bottle (thick) are the two we use most often.
- Adhaero 2-part 5-min epoxy. It's from the dollar store!
...A Body or Spot Filler.
Body filler (also known as Bondo, spot filler, glazing putty, scratch filler, etc.) is a compound meant to be spread on a surface to fill in gaps, scratches and defects, left to dry, and then sanded down again, leaving the gap filled and even with the rest of the surface. This can speed up the sanding process by filling in deep scratches rather than sanding them all the way down, and it's also instrumental in filling in seams where you join one print to another.
Fillers come in many forms. Some are meant for large surfaces and large gaps, like Bondo's Body Filler, and others are meant for small detail work, like Spot Putty, and others are meant for perfecting a fine finish, like a glaze. They all have their strengths and weaknesses.
For beginners, we suggest starting with something premixed that comes in a tube, like 3M's Acryl-Green (a favourite here) or Bondo's Glazing and Spot Putty. These are a little more expensive than a big container of a two-part filler, but you can dispense them out of a tube without needing to mix anything. Two-part fillers like Bondo's Body Filler are often much cheaper, but they involve having to mix the filler with a hardener, and calculating the ratios between filler and hardener can be tedious, especially when you can only mix up what you're going to use in the next 5 minutes at a time. The two-part systems are often also more odorous and require you to open a whole can of it to dispense, so it can be messy on top of having more fumes.
Some people use spot filler liberally, as if they are frosting a cake, and then sand it all down again. This is handy if you want to fill a really rough print really fast, but it uses a lot of material and also creates a lot of dust, as anything you apply then has to be sanded back off. Caked on spot filler can also fill in the finer details of your print, like an engraving, so liberal usage is best for big, low-detail pieces with lots of smooth planes. In the image above you can see how we've used the spot filler to fill in the concave print lines on this Holy Sword of Valis prop.
If you don't want to buy these specialty products, you can mix baby powder and superglue to form a very fast-curing, durable spot filler. This is harder to sand back down but it is much stronger, and you can adjust mix ratios to choose how runny or thick the paste is. Just remember it cures very fast, so only mix up very small batches at a time.
You can also skip this material entirely if you'd rather not use it. You can sand things perfectly smooth without it, it just takes a lot longer.
Our brand recommendations for 3D Print-friendly spot-filler:
- 3M's Acryl-Green. Affectionately nicknamed "toothpaste" for its minty colour, this is our favourite spot filler. Difficult and expensive to find outside of the USA; if you're a Toronto local, reach out and we can possibly hook you up.
- Bondo's Spot Putty. Same as above, really, we just don't like it as much and it has a much stronger odor. Its slower cure time can be more forgiving for beginners.
...Primer and Filler Primer Spray Cans
The Dangerous Ladies brand of choice is Duplicolor for filling and sanding 3D Printed Cosplay Props.
Primer is typically a base-coat layer of paint used to smooth out the top of a surface to prepare it for paint, and later, to increase adhesion between a surface and the paint being applied to it. At this stage, primer is applied to help you see imperfections in the surface of your print. Because sanding can make the surface of a print difficult to examine close-up, a layer of primer is a uniform colour that makes remaining blemishes easier to see.
A filler primer is a high-build version of primer; it goes on thicker so it can fill scratches and nicks and print lines easier. Filler primer is applied between sanding rounds to reduce sanding time. As primer can be expensive and will largely be sanded off, we suggest using it after the initial rounds of sanding, somewhere between 320 and 400.
If you are buying multiple cans of primer, we suggest getting a few different colours. (Grey and red-brown are most common, but white and black exist too.) This is so that you can alternate colours through sanding and see how far you've gotten. For example, if you sand a bit, spray with red, sand a bit, spray with grey, and then sand and release you can see the red again, you know you've sanded all the grey off and are a point where it's either smooth, or needs a deeper spot filler.
Like all spray paints, primers can NOT be used indoors. You can skip this material entirely if you'd rather not use it or don’t have the set-up to use spray paints. You can sand things perfectly smooth without it, it just takes a lot longer.
Our filler primer recommendations:
- Duplicolor's Filler Primer
- Duplicolor's Sandable Primer
- Value primers:
- Rustoleum's Filler Primer: A less expensive option compared to the Duplicolor models
- Personal protective equipment
- A dust mask
- A bucket or receptacle for water
- Warm water
- Dish soap
- A craft knife
- Wet-Dry sandpaper in 150 grit
- Wet-Dry sandpaper in 220 grit
- Wet-Dry sandpaper in 320 grit
- Wet-Dry sandpaper in 400 grit
- Wet-Dry sandpaper in 600 grit
- Body filler or spot filler
- Super glue
- 2-part 5-min epoxy
- Spray can primer
- Spray can filler primer