Methods for post-processing 3D models

FDM printing technology, in which the vast majority of lines are flat, makes post-processing of printed products an important step. This procedure is especially often required when the surface of the printed product needs to be flat.

Post-processing 3D models

Post-processing is a process that takes place after the product has been printed. It is necessary for the layer-by-layer printed 3D-model had the highest quality appearance, without irregularities and flaws.

Post-processing not only makes the product look more professional. But in some cases it makes it more durable, changing the elasticity parameters of the material, its density, as well as some structural and textural features.

How to process the model after 3D printing: step-by-step instructions

Processing of finished products after the printing is completed, can be carried out by different methods. The choice of method depends on the final goal and the features of the filament with which the product was printed.

photo of a plastic part

Removal of supports

If the part was printed using support structures, the first priority in the post-processing phase will be to remove them. The processing method depends on the soluble or insoluble material used to create them.

IMPORTANT: In contrast to other methods of final machining of parts, removal of supports is an obligatory measure. Thus their removal does not guarantee improvement of quality of a surface of an object.

To carry out the removal of support structures printed with insoluble materials, you will need the following tools:


A set of brushes that have bristles of varying degrees of hardness.
The material from which the supports were made can be easily removed from the surface of the product. This process does not require serious effort. In places with difficult access (recesses, holes, etc.), you can remove excess layers by using pliers or a brush.

This method of post-processing does not affect the geometric proportions of the manufactured object, but during cleaning it may leave traces on its surface, which can be removed during further processing using other methods.

Supported product printing almost always leaves traces on the surface of the object. This not only degrades the appearance of the product, but also reduces the accuracy of printing in case the 3D printer is not set up well enough.

photo of the parts


Once all supporting structures are removed, the item can be sanded. This will not only level the surface, but also make it smooth and remove obvious defects and marks left where the product was in contact with the supporting structures.

The choice of sandpaper depends on how thick the layer was when printed, as well as the quality of the finished product.

For example, if the thickness of the layer is 200 microns, a sandpaper marked P150 is suitable for post-processing. If there are obvious defects on the product, and the layer thickness was 300 microns and more, it is necessary to start with P100 sandpaper.

The sanding process can be continued with a change of grit up to P2000.

IMPORTANT: During sanding, the surface should be cleaned with brushes, soapy water and a soft sponge. This will remove dirt, dust, and improve the quality of processing.

Remember that sanding is recommended to be performed in a circular motion, brushing the entire surface of the product. Parallel or perpendicular movement of the sandpaper should be excluded – it can lead to the formation of deep grooves and scratches.

After the sanding stage is completed, the surface will acquire the necessary smoothness, and the further stages of post-processing will be much easier.

The disadvantages of the method include the impossibility of using it for parts that have one or two shells because of the high risk of damage to the print, as well as the difficulty of using the method if the product has a large number of small parts.


Filling of voids

After the supports have been removed and the part has been sanded, voids may appear on the surface of the part. This defect can appear directly during printing in cases where the layers are incomplete for some reason.

Small gaps and voids can be filled with epoxy, and large defects, often occurring when printing a large product consisting of several parts at once – with a special filler used for bodywork. However, this method has a significant disadvantage – the filler used for bodywork repair, like any other polyester epoxy, when drying leaves discolored areas on the product.

IMPORTANT: After filling the voids, the part should be cleaned again.

Filling voids in the printed product can also be done with putty. The part where the voids are filled with it can be easily sanded and subsequently painted. In addition, the voids filled with filler acquire additional strength, which positively affects the performance of the product.

In case the printout was made with ABS plastic, the voids can be filled with a special liquefied ABS. Once filled, the solution reacts with the cavity walls and seeps into the voids.

Dichloromethane is also a popular medium and is suitable for most types of filament, including ABS, PLA, HIPS, SBS, etc.

How to primer?

After the printed product is stripped, it can be treated with primer. To do this, you will need:

  • A lint-free material that will be used to wipe the item.
  • Toothbrush.
  • Sandpaper with grit 150/220/400/600.
  • Plastic primer (preferably using an aerosol).
  • Polishing sticks.
  • Paper for polishing.
  • Personal protective equipment – mask and gloves.

IMPORTANT: the method is suitable for all types of filaments.

After you have prepared the piece, from a distance of 20-25 centimeters treat its surface with the primer, evenly applying the primer. After the primer has dried, the irregularities must be rubbed down with a sandpaper with granularity P600, after that the second primer coat is applied.


When the primer coat on the product is completely dry, you can begin to apply paint.

IMPORTANT: you can paint the product printed on a 3D printer with any tools, but the smoothest result is achieved with a spray gun.

When painting, it is not recommended to use aerosol paints intended for household use. As a rule, they are highly viscous and their application is quite difficult to keep under control. The best option would be to use paints designed for painting models.

The paint application should also be done in layers, with each successive coat applied only after the previous one has dried completely.

When the object is painted, wait until it is completely dry and then apply buffing paper. After using it, the coating will shine.

IMPORTANT: Do not shake the can while applying paint. The mixing of the propellant and pigment leads to the formation of bubbles that reduce the quality of the coating. It is recommended to rotate the can in a circle for a few minutes to mix the paint by rolling the mixing ball.

Epoxy Coating

To coat the product with epoxy resin, you will need:

  1. Epoxy resin (two-component).
  2. An applicator for applying the compound.
  3. Container in which ingredients will be mixed.
  4. Sandpaper marked P1000 or higher.

The treatment must be performed in several stages:

  • Stripping.
  • Mixing the resin and hardener. The use of a glass container is not recommended because the resins have high exothermic characteristics.
  • Mixing the resin and hardener. Mixing should be done smoothly to avoid air bubbles in the composition.
  • Application of the first layer of resin. At this stage it is necessary to minimize the number of irregularities on the product.
  • Once the first layer of resin is fully cured, you can begin applying the next layers.
  • When the result is achieved, the product should be sanded with sandpaper.

photo of the figurine

Removal of soluble supports

If soluble filaments were used when printing the support structures, you will need to remove them:

  1. A container of sufficient volume.
  2. Solvent.
  3. Typically, the process involves placing the printed part in a container of solvent just long enough to dissolve the supports. Any container made of non-porous material can be used for this purpose.

IMPORTANT: The process can be accelerated by using an ultrasonic cleaner, heating the solvent, and replacing it in a timely manner.

Cold Welding

The cold welding method involves the use of the following materials:

  1. Acetone (for ABS plastic).
  2. Adhesive (for PLA filament).

The method is used when the product is too large to print at one time. In this case, the model is divided into several parts, which are subsequently connected to each other.

For PLA-filament assembly is made with Bond-O glue or other suitable compounds, and for ABS components are attached to each other with acetone.

The surfaces prepared for joining are lubricated with bonding compound and pressed together. They should be held together until the chemical reaction is complete.

What is used for sanding and polishing?

The materials used for sanding are:

  • Soft cloths.
  • Sandpaper with different types of grit (from P100 to P2000).
  • A toothbrush.
  • Soapy water.
  • The initial grit size of the sandpaper depends on the layer and quality of the print.

Grinding is carried out up to grit 2000. The model should be moistened regularly during processing. This will help reduce friction and help keep the sandpaper clean.

For polishing, the following are used:

  • Special compositions for polishing polymeric materials.
  • Sandpaper with a grit from P2000.
  • Material for wiping.
  • Polishing wheel.
  • Microfiber cloth.

IMPORTANT: Do not polish the surface if you intend to paint it. After polishing, the primer and paint will not adhere to its surface.


The smoothing procedure can be done for all FDM thermoplastics. This will require:

  1. A solvent-resistant container.
  2. Wipe cloth.
  3. Solvent.
  4. Aluminum foil.
  5. Personal protective equipment.

The bottom of the container should be lined with paper towels and a small amount of solvent should be applied. It is important to lightly wet them, not soak them.

Acetone is good for ABS, dichloromethane and other compositions are good for PLA. In the center of the soaked towels should be placed a stand made of foil, and put the printed product on it.

Then the container should be sealed hermetically. Polishing with solvent vapors can take different amounts of time, so it is advisable to check the workpiece from time to time, so as not to miss the right stage.

You can speed up the process by gently heating the container.


Metallizing products allows you to give your workpieces the appearance of metal products. To perform this method of post-treatment, you will need:

  • Galvanizing solution.
  • A consumable anode.
  • Conductive paint.
  • Acetone with graphite.
  • Power rectifier.
  • Screw made of conductive metal.
  • Container not conductive.
  • Contacts.
  • Non-conductive safety gloves and goggles.

Electroplating can be done at home using copper or nickel. It is extremely important that the surface of the item be as smooth as possible. Any irregularities after treatment will be reinforced, which will spoil the appearance of the product.

The procedure takes place in several stages:

  • Preparation of the surface of the product.
  • Application of conductive paint.
  • Connecting a screw or hook with an eyelet to the minus contact of the rectifier.
  • The anode must be connected to the plus contact of the rectifier.
  • After turning on the rectifier, the printout is dipped into the vessel.
  • Next, the voltage should be set to 1 to 3 volts and wait for the product to be metallized.

When the process is complete, the product should be removed from the container and coated with a varnish designed to protect against corrosion.
photo of the product

How to polish transparent plastic and make it glossy?

Polishing transparent plastic is made with the help of sandpaper with a grain size over P2000 and special compositions for polishing. For processing small parts, it is recommended to use polishing wheels or other rotary tools.

Mistakes of post-processing and how to avoid them
The most popular mistakes made by users during post-processing are:

  • Overexposure. If the wall thickness is insufficient – it’s easy to rub the walls to holes when polishing and sanding.
  • When working with adhesives or solvents, precautions should be taken: work in well-ventilated areas, and use a mask, goggles, and goggles.
  • When sanding PLA plastic you should not be in a hurry – the material can roll off under the influence of sandpaper.
  • If machining parts after chemically treating them, wait until the coating is completely dry.
  • Before applying primer and paint the surface should be thoroughly cleaned from dust and particulate matter.

Post-treatment is an important process that can give the printed product its final shape and make it more durable and of higher quality.

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