The possibilities that 3D printing unlocks for all of us are amazing and as time goes on more and more technologies and more use cases for 3D printing are found and developed. But one problem remains and will probably remain for quite some time and that is smoothing the print because you will probably see at least some print lines or have some kind of residue from supports. In this article, I will tell you how to smooth any kind of 3D print as easily and effectively as possible.
As a whole, the best way to smooth a 3D print is by applying a spray-on filler to the print and then sanding the surface until it is smooth enough. Alternatively, ABS can also be smoothed by using Acetone and PVB can be smoothed by using Isopropyl alcohol.
If you don´t know how any or some of these methods actually work then don´t worry as I will explain exactly how to smooth your 3D prints in the following.
How to Smooth 3D Prints by Sanding Them
First up is the one method that I use the most and I also recommend it to every beginner. Sanding the 3D printed model.
But I have a slightly different approach that will speed up the whole tedious work a little bit and remove some of the tedium from sanding a whole model.
To smooth a 3D printed part it is important to start with rougher 120-grit sandpaper first to remove uneven parts from the surface before moving on to 200 grit and finally 320-grit sandpaper. Applying a coat of spray-on filler before sanding the 3D print will make the whole process easier and faster.
The reason why I recommend this method of smoothing 3D prints for most projects and especially for beginners is that it is the easiest method and you don´t require any hazardous liquids like Acetone or Isopropyl alcohol.
Here is how I usually sand my 3D prints.
First I use some rough grit sandpaper and files to remove filament threads or residue from supports.
Then I usually apply a spray-on filler to fill in any small uneven parts and to remove smaller layer lines.
You can get spray-on filler in your local hardware store in the paint section where the car paints are or right here on Amazon.
The filler is much easier and faster to sand which makes the whole sanding part less tedious and much faster.
I tend to work my way up to finer grit sandpaper. Usually, I will start with 120 grit, then move to 200 grit, and if I want the surface to be really smooth then I will sand the 3D print a final time with 400 grit sandpaper.
Finally, I will apply a primer to prepare the 3D print for painting. I have a whole guide on how to paint 3D prints including what kind of paint to use that you can read right here.
Pros:
- An easy method to smooth prints
- No hazardous chemicals required
- Most affordable option
Cons:
- Very time-consuming process
- Requires a lot of patience
How to Smooth PLA Without Sanding
A lot of people find sanding very tedious and annoying and I completely understand that because I feel the same way. Luckily there are other ways to smooth 3D prints but they tend to involve hazardous liquids which is why I don´t like this method and why I don´t recommend it for most beginners.
As a whole, 3D prints can be smoothed by using either epoxy resin to fill in any uneven parts and print lines or by applying a solvent such as Ethyl Acetate to slightly melt the surface of the print which will smooth it.
I don´t recommend using Ethyl Acetate at all because it is very hazardous and you need to know what you are doing when working with it.
Epoxy resin is also a little more difficult to work with but not nearly as dangerous as Ethyl Acetate. But if you want to know how it is done then read this article from bitfab.io.
Epoxy resin is liquid and will fill in any uneven parts in the print before hardening after about 24 hours. Once the resin has hardened it will be very rigid and if you see any uneven surface details then you can still remove those by sanding the resin layer.
It doesn´t matter which method you use you should still apply a primer before painting the print to ensure that the paint permanently sticks to the surface of the print.
Pros:
- Requires very little manual labor
- The resulting surface is very smooth
Cons:
- Requires the use of hazardous chemicals
- The chemicals can be hard to get
- Expensive compared to the other methods
- Some detail on the 3D print might get lost
How to Smooth ABS with Acetone
This is one of the most well-known methods for smoothing 3D prints.
To smooth ABS with acetone simply suspend the model on a metal tray or metal grid in a plastic container and fill some acetone in the bottom of the container. Close the plastic container with a lid and leave the 3D model in the container for 15 minutes. Take the model out and let it dry for an hour.
The biggest downside to this method is that most 3D printers have a hard time printing ABS.
The printer needs to be enclosed to reliably print ABS and most cheap to mid-prized 3D printers usually aren´t enclosed.
This method of smoothing ABS works because acetone dissolves ABS. We are basically slightly melting the surface of the ABS plastic to remove any layer lines and effectively smoothen the surface.
The longer you leave the model in the container with the acetone the more it will be dissolved.
When you take the model out of the container then the model will be slightly tacky. So don´t touch the model directly with your hands or you will leave fingerprints on the surface.
Let the print dry outside the container for one or two hours until the ABS plastic has become rigid again.
This process will also make the surface of the print quite shiny.
Pros:
- The print will be very smooth
- Requires very little manual work
Cons:
- Requires the use of hazardous chemicals
- The surface will be shiny after smoothing it
- Only works on ABS plastic
How to Smooth PVB (Polysmooth) with Isopropyl Alcohol
This is a less-known alternative to ABS and acetone. You can smooth PVB filament with isopropyl alcohol.
To smooth PVB (Polysmooth) with Isopropyl alcohol simply fill some Isopropyl alcohol in a small spray bottle and mist the 3D print with the alcohol. The surface will melt after a short while smoothing the surface.
PVB is very similar to PETG or PLA plastic.
So this filament can be printed quite easily and does not require an enclosure.
PVB is often sold as Polysmooth or Fybersmooth filament which makes it a bit hard to find sometimes.
The biggest disadvantage of PVB is its price. It is almost twice as expensive as PLA.
The reaction of Isopropyl alcohol and PVB is quite slow. This means that you will need a little bit of patience before you see any results after spraying the alcohol on the 3D print.
This method will also not cause the print to become shiny. Instead, the print will become smooth and will stay matt.
Pros:
- Isopropyl Alcohol is cheaper than Acetone
- The chemical reaction is easy to control
- PVB can be printed by pretty much any regular printer
Cons:
- PVB is very expensive
- The chemical reaction is very slow
Smooth 3D Prints with PU Varnish
PU Varnish is usually used to seal wood but it can also be used to smooth 3D prints.
To smooth 3D prints with PU varnish, simply apply the varnish to the surface of the model with a brush. Make sure that the varnish is applied evenly and don´t apply too much of it at once.
The varnish will usually take several hours to cure fully.
Once the varnished has cured you can sand it, paint it, or simply leave it as it is.
This method works on almost every type of plastic.
Pros:
- Varnish is cheaper than resin
- Varnish is not toxic
Cons:
- Varnish takes a while to cure
- It´s hard to apply it evenly
Smooth 3D Prints with White Craftsglue or Mod Podge
This has become one of my favorite methods for smoothing 3D prints.
To smooth 3D prints with Mod Podge simply mix the Mod Podge with some water before applying the mixture directly to the surface of the print. Apply the glue in multiple thin layers and let it dry overnight.
Mod Podge can be sanded and it can be painted. You will need to use a Primer before painting the model though.
Instead of Mod Podge, you can also use White Craftsglue. Just make sure that it dries transparently unless you plan to paint the model anyways.
Pros:
- Very cheap
- It is the easiest method to smooth 3D prints
- Works on complex models
Cons:
- Takes a while to fully dry
Smooth 3D Prints with UV-Resin
I already mentioned that there is a way to smooth 3D prints with resin but instead you can also use UV resin. If you have a resin printer then you will probably have some UV-resin close by.
To smooth 3D prints with UV resin, simply apply a thin layer of UV resin to the surface of the print and cure it with UV light. Make sure to apply multiple thin layers and cure them in-between layers to avoid surface imperfections.
UV resin is slightly toxic, however, so you should always wear a protective mask and gloves when working with resin.
This method will give you very smooth surfaces but it also takes a little bit of patience and careful application of the UV resin to succeed.
Pros:
- Very smooth surface finish
Cons:
- Resin is toxic before it is cured
- Resin is expensive
- Resin is difficult to work with
Smooth 3D Prints with a Heat Gun
If you have a heat gun at your disposal then you can use it to smooth the surface of your 3D prints.
Smoothing 3D prints with a heat gun is pretty straightforward. point the heat gun at the surface of the 3D print and make sure to move the heat gun constantly to keep it from burning the print at one location. The surface of the print will melt slightly resulting in a smoother surface in the end.
This method works best on PLA but can also be used on ASA and ABS.
Just be careful not to burn yourself or your print.
Pros:
- Fast and easy
- Only requires a heat gun
Cons:
- You could burn yourself
How to Efficiently Remove Layer Lines on 3D Prints
Probably the most annoying part about 3D printing is the layer lines. It doesn´t matter how well you adjust your 3D printer some layer lines will always be visible unless you are using a resin printer that is. So how do you remove these annoying layer lines?
To remove layer lines on 3D prints the print either has to be sanded, coated with epoxy resin, or the surface has to be slightly melted with a chemical solvent. The safest method is applying a spray-on filler and then sanding the print.
My personal favorite method is using a spray-on filler and then sanding the whole print to make it smooth and remove any layer lines.
Using epoxy resin to coat the whole print is also a viable solution but I only recommend this method for people that have experience with resin.
Using chemical solvents is by far my least favorite method as it usually leads to some surface details being lost and you have to handle quite hazardous liquids.
If you want to use this method however then consider reading this guide by bitfab.io.
Hi, I am a passionate maker and professional prop maker for the entertainment industry. I use my woodworking, programming, electronics, and illustration know-how to create interactive props and puzzles for Escape Games and marketing agencies. And I share my knowledge and my experience on this blog with you so that you can become a maker yourself.