If you want to improve the surface and aesthetics of your 3D prints, you have several options. In this 3D printing post processing guide, we’ll show you the methods that work.
3D Printing Post Processing
One of the major disadvantages of 3D printed models is their rough, rippled surface. The roughness is caused by the layering of the melted filament. While you cannot achieve a different result if you are using the common and inexpensive FDM printing technique, the models can be post-processed to look better.
Generally, resin 3D printers produce prints that are smoother than those made using FDM 3D printers. If interested in resin 3D printing, check our guide of the best resin 3D printers.
But if you already have an FDM 3D printer, there are still ways in which you can improve your models. Read on to find out.
Presets
The following applies to all types of filaments. Make sure you set the slicing software properly. Reworking an uncleanly printed object is more time-consuming than one that has been printed properly.
The lower the layer height, the smoother the finished print will be, and the less post-processing that will be required. Printing time is significantly longer with a high resolution. However, the time investment is worth it. Models printed at a high resolution look significantly better without post-processing.
The print must also be sufficiently stable for post-processing. This requires at least three to four outer layers and sufficient filling (infill).
Post Processing PLA
The first step after printing is removing the support material, i.e. the supports that are also printed on models with an overhang. If you have set up the slicing software properly, you shouldn’t have any major problems. In practice, you can use needle-nose pliers and a craft knife to remove the support material.
Next, you have to eliminate the threads created during printing (stringing or oozing ). In practice, this works with objects with straight lines, for example, with a deburring tool. Sandpaper can also be used on prints with many curves. Modifi3D, which is a special post-processing tool for 3D prints, did not convince us in practice. When using it, we damaged our prints more than we improved them.
Then it’s time to tune the surface. You can use sandpaper to smoothen prints with large surface areas. If you have to grind a lot of flat surfaces, it is best to use an electric hand grinder. However, be careful. If you grind in one place for too long, you will soften the temperature-sensitive surface.
In practice, we recommend a grit of 80 to 140 for rough work. A much finer variant is then required for fine work (e.g. K400). With an even surface structure and the use of wood filament, for example, this is often enough to achieve very impressive results.
If you want to smooth small and hard-to-reach areas, you will quickly reach your limits with sandpaper. In practice, you can use Dremel with appropriate attachments.
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Inexpensive replicas of the original Dremel are available for cheap, and are sufficient for working with plastic. However, be careful when working; a high a number of revolutions and strong pressure destroy the relatively sensitive plastic surface or can make the material to melt.
If you have larger gaps in the printed image, first work on and smooth out the areas with a fine plastic filler. This will save you from the tedious grinding work and also leads to a decent result. However, the putty will be visible. If you work with putty, you should paint or varnish the print afterwards.
Smoothening ABS Filament
A convenient way of finishing ABS filament models is possible. We are referring to vaporization with acetone. The idea behind it is simple: acetone attacks the plastic and dissolves it.
If you only steam the finished print result with the solvent for a short time, the outermost layers will soften and the visible layers merge together. After the procedure, you will be left with a shiny and smooth surface.
However, there is a disadvantage with this method: It only works with ABS filament. As you know, cheap printers without a heated print bed cannot process ABS filament. Moreover, acetone vapor is hazardous to health.
Using a Spray Spatula
If there are hardly any straight surfaces in your print object, or if manual sanding seems too time-consuming, you can work with spray spatula from the spray can. The procedure is simple: apply spray spatula evenly and in layers. The individual layers must not be too thick, or else drops will form.
Depending on the surface, at least four to five passes are necessary to achieve a decent result. Between the individual work steps, the applied material has to dry again and again. This takes at least 30 minutes each time.
Anyone who then still recognizes individual layers of the print can rework with sandpaper and then apply two more layers of the spray spatula. The result is a smooth and even surface structure that is perfect for varnishing or painting. Details of the print are very well preserved. No other method is better suited for very detailed prints.
This method also has some disadvantages. For one, it takes a lot of time. Also, you cannot work with spray cans in the apartment, since the spray filler smells like paint and leaves a huge mess.
Finishing with Epoxy Resin
Finishing with epoxy resin is a little less time-consuming. The two-component resin is significantly more viscous than spray putty and can be applied with a brush. In practice, two layers are enough to completely smooth objects. However, for this to work, the resin must be meticulously measured out when mixing. In practice, a cheap precision scale helps.
In addition to standard epoxy resin, the trade offers special 3D printing epoxy. This is significantly more expensive, but delivers excellent results with just a single operation. The standard resin that we also tested is a bit thinner. Therefore, a second step is necessary for a perfect finish.
However, epoxy resin has some disadvantages. For example, small details are lost and ironed out. If you don’t want to varnish or paint the finished object after smoothing, this method is still the best choice. Although individual print layers and details are still visible, the surface is still perfectly smooth and glossy.
Lacquering and Painting
If you want to paint or varnish your smoothed 3D prints, you should keep a few things in mind. For example, the objects must be free of dust and grease before the paint is applied. Epoxy resin surfaces should also be primed or at least sanded.
If you want to paint your objects, use acrylic paint and a brush. It’s easy and cheap to use, but takes time and practice. After painting each color, allow a short drying time. You can even apply thick paint to enable you to repair small bumps in the surface. Using a primer or a spatula will help you to achieve good coverage. However, acrylic paint also holds and covers completely untreated prints.
If you prefer to work with a spray can instead of a brush, prepare thoroughly beforehand since standard paint doesn’t even level out small bumps. Moreover, not all paints are suitable for plastic. If you are not sure, get an appropriate primer.
You also have to take a lot of time when painting. The layers may only be applied thinly and must always dry sufficiently.
In addition to standard paints, effect paints, for example with a stone look, also achieve very interesting results. The smooth surface is lost, but details are still clearly visible. In practice, the glitter paints are also well received. The interesting look also distracts from less than perfect printing results.
In order to achieve high durability, the finished painted object should be protected with a layer of clear varnish. That will look even better.
Conclusion
If you want a perfect, smooth surface for your 3D prints, you have to invest a lot of time and do manual work. The more meticulous you prepare, the nicer the end result will be. This starts with the print settings and ends with painting.
