Surface treatment of 3D prints
PLA print with a textured or smooth surface?
|
When printing on FDM printers , typical thin layered lines are created on the surface of the prints. And at this moment comes the time to ask yourself a question - leave a textured surface or smooth? There are many reasons why a smooth surface would be the better choice. Of course, it can be about aesthetics and you simply like the smooth surface better. But one of the other reasons is that a smooth surface reduces friction on moving parts. Which may be desirable in many cases. PLA material, or polylactic acid in Czech, is one of the most commonly used filaments, but it has one major disadvantage when it comes to additional surface treatment. And that is the impossibility of using acetone, which is quite popular with other types of filament. You may have come across various videos on the internet where users tried to smooth out PLA prints with acetone and it didn't go well. In the best case, the surface did not change at all (when using acetone fumes), and in the worst case, the prints were completely damaged (when leaching the print in an acetone bath). But still, you don't have to completely hate acetone for PLA filament, it will come in handy instead of classic instant glue, because it sticks the prints together without a problem. |
 |
In addition to acetone, of course, there are other chemicals that could handle PLA easily, but due to the fact that some of them require a special permit, they are not very available for the regular user. If you still don't want to give up the idea of chemically smoothing the surface, there is a tabletop polisher available on the market that creates a fine alcohol mist to smooth the surface. But the manufacturer does not directly state that the device is primarily suitable for PLA filaments, and the initial investment is not negligible.
Other ways to achieve a smooth and shiny surface come next. We are talking about cutting , grinding , melting or painting .
And now to the heart of the matter - how to properly smooth PLA prints?
Grinding
Grinding is one of the most used ways to additionally modify a PLA filament print. The reason is simple – it is the most affordable solution.
|
Wet grinding is a specialty . The principle of sanding is the same, only you need to wet the sandpaper from time to time. By continuously soaking high-grain paper, you can achieve a smooth surface that will shine. Alternatively, it is possible to get an electronic sander that can handle both wet and dry sanding, but you have to expect a higher initial investment, so it is worth considering whether an electronic sander is really worth it. With sandpaper, its roughness is decisive , which is indicated by the number of abrasive grains per square centimeter. Most often, it ranges from 40 grains/cm 2 to about 4,000 grains/cm 2 . So the more you need the surface to be smoother and shinier, the more gritty sandpaper you need to use. |
 |
For grinding you can use:
advantages : fast, physically easy |
disadvantages : higher initial investment, not suitable for details |
advantages : fast, ensures even sanding of print and sandpaper, comfortable to hold in the hand |
disadvantages : not suitable for details |
advantages : cheap, possibility to cut to your desired size |
disadvantages : takes longer, more physically demanding |
advantages : cheap and available, ideal details |
disadvantages : takes more time, can be physically demanding |
 |
 |
 |
 |
Additional treatment using a rotary multi-function sander
If you have a sander available, don't be afraid to use it. The principle of surface treatment is quite similar to that of a knife. Only with the advantage that the grinders have handles of different sizes in the set. So if you use a small attachment, you can better get to the inside of the print or other hard-to-reach details.
Two basic tips will come in handy when sanding prints with a rotary sander:
- speed of rotation - for the desired result, do not apply too much pressure, but rather increase the speed of rotation of the revolutions.
- generated heat - this is working with electrical equipment that generates heat as it rotates, which could melt the plastic and leave marks on the print. Therefore, do not use the sander for too long in one place.
Some attachments may work too hard and damage would occur again. In short, if you're going to use a sander to refinish PLA prints, you'll need to experiment with different attachments and spin speeds, and it may take a while to get the hang of it to get the results you want.
Additional treatment with a knife
You will be well served by a classic pull-out or paring knife , which we probably all have at home. There are different types of knives on the market, but focus mainly on the size of the blade. No matter how you work with the knife, the basic rule is: always cut away from yourself . It is good to remember the well-known saying that sometimes less is more . In this case, it is recommended not to press too hard on the knife to avoid removing too much of the print than originally intended. Especially if you are going to glue multiple prints together, you could be missing the connecting part. If you don't have a knife handy, you can use a razor blade, but even then, be careful.
Surface melting
Another option for modifying the surface of PLA filament prints is surface melting. It is widely known that PLA filament is not very heat resistant and is therefore not suitable for external use. However, you can use this feature when editing prints.
A heat gun will be most useful for melting the surface of the print. Set it to the lowest setting and move slowly and smoothly over the print. If you are able to place the print on a turntable that will be ideal. Thanks to this, you will avoid uneven melting, which could damage the print in places. You might think of using hair dryers for surface melting, but since most hair dryers do not reach the desired temperature, you will not get the desired result.
Painting
Whether you spray, paint or dip in paint, finishing with varnish is an interesting choice. The paint can fill in small defects and lines between layers to achieve a smooth, even and shiny surface. If you are gluing together the final product from several prints, it is a good idea to plan what colors the prints will be in before you start coloring. To avoid unnecessary taping of the part of the prints that you do not want to color.
Coloring can be divided into two basic types:
- undercoat
It works on the principle of smoothing the surface of the print and creating a uniform layer. After drying, sand the varnish so that the surface is sufficiently smooth and shiny. The advantage of sanding the varnish over sanding the PLA print directly is that the varnish is more pliable and softer and sands better. Of course, it can only start with the primer. You can apply several layers of primer to the print and then continue with additional colors (ideally from the smallest details to large areas). You should finish everything with varnish, which will ensure a long life of the paint. Don't forget that coloring is quite time-consuming. And that's because you have to let each layer of paint or varnish dry.
- coloring with epoxy
Epoxy works in much the same way as a primer, except that it better covers and fills in various unevenness and print lines. But the preparation of staining with epoxy can take a little more time than with conventional paint, because you have to mix the epoxy before using it. Epoxy is applied with a brush. It is necessary to ensure that the brush strokes are uniform and that no visible transitions remain on the print. Allow the print to harden after applying the epoxy.
Once you have the base layer of the print ready, you can play around with the next adjustment:
|
 |
And now it's just time to love your work. If you are not satisfied with the result, you can boldly start editing the next print from PLA filament, because it is not for nothing that they say that practice makes perfect .