Jun 20, 2018

FDM 3D Printing Post Processing – An Overview for Beginners

FDM 3D prints generally have a rough surface finish, which is visible to the eye, but they can be easily post-processed to achieve the desired look and feel. Throughout this article, we highlight 3D printing post-processing techniques to help you get the best out of your FDM 3D prints.

Technique #1: Support Removal

Dissolvable support structures are easier to remove, but require a dual extruder printer Source: All3DP

Even though support removal is a must in FDM 3D printing, proper planning can greatly improve final surface quality. This is done through eliminating unnecessary material waste and complicated supports, which may leave marks on the print surface.

Supports can be of two types: soluble and insoluble. Let’s look at them one by one.

Soluble: Soluble materials dissolve in water or specific chemicals. HIPS, generally used as a support with ABS material, dissolves in a chemical named D-limonene. The print is dipped in the chemical and the support printed with HIPS material will completely dissolve, leaving only the necessary part. Another material, PVA, is generally used as a support with PLA material and dissolves in water.

Naturally, these types of supports make removal much easier than the usual push-pull-tug method of removal using clippers (or fingers).

Insoluble: Insoluble materials are the normal printing materials like PLA, ABS, Nylon, or PC. These materials are typically used for prints as well as their supports when using a single extruder. Such supports are removed by hand or flush cutters.

Sometimes these supports are easy to remove but, if generated in critical locations, they can be difficult to remove and may damage the print.

Soluble or insoluble, support structures still leave marks at the touch points of a print. These can be further post-processed to achieve a smooth and even finish.

Pros & Cons of Support Removal

Pros:

  • It’s the easiest method of post-processing.
  • It requires minimal equipment.
  • Soluble supports provide greater flexibility of design.

Cons:

  • Supports at critical locations are difficult remove.
  • Supports can damage the part during removal.
  • Insoluble supports can restrict the design freedom of the product.

Technique #2: Sanding

Sanding a primed 3D print Source: Pierre Fontaine / All3DP

Sanding is the most common 3D printing post-processing method. It’s accomplished using sandpaper of varying grits. The usual process is to start with a low grit sandpaper and then move up, in stages, towards higher grit sandpapers (for example around 2000 grit).

Pros & Cons of Sanding

Pros:

  • It requires minimal equipment.
  • Even the roughest of prints can be smoothened via sanding.
  • Any FDM material can be easily sanded.
  • Post-processing costs are minimal.

Cons:

  • It takes time and effort.
  • It affects the part’s dimensional accuracy.
  • It’s difficult in critical locations where a part may have tiny features.
  • It sometimes releases fine particles of the material in the air, which can be inhaled.
  • As a manual process, sanding may be uneven on different faces of the print.

Technique #3: Acetone Smoothing

Enthusiasts can use the Polysher from Polymaker for acetone smoothing Source: Polymaker

Acetone smoothing is a popular 3D printing post-processing technique for ABS material. It involves the 3D printed part being exposed to acetone vapors in a closed environment (generally in a glass enclosure). The vapors react with the outer layer of the print and melt it. This results in layer lines fading, which indirectly smoothens the outer layer of the print and gives it a shiny look.

Pros & Cons of Acetone Smoothing

Pros:

  • Acetone smoothened prints look shiny and glossy. (Great for gifts!)
  • Acetone is relatively cheap so post-processing costs are low.
  • The process is fast and relatively simple.

Cons:

  • It only works on ABS material.
  • Acetone is a toxic chemical, so proper precautions have to be taken before using this 3D printing post-processing technique.
  • It requires a well-ventilated area and constant observation.
  • There is no control over the amount of material removed through the process.
  • It affects the dimensional accuracy of the part.

NOTE: Acetone is a highly flammable and can explode. Therefore, proper precautions should be followed while carrying out this process. Even acetone fumes are harmful if inhaled, causing irritation and other negative effects. The process must be carried out in a well-ventilated area.

Technique #4: Priming & Painting

Spray painting a 3D printed skull Source: All3DP

Priming simply means coating the part with a primer paint or a primer spray. It acts as a base layer that prepares the surface for the desired paint. This 3D printing post-processing technique can significantly enhance the look and feel of the product.

For priming, it is recommended that the product is sanded first with a low and medium grit sandpaper. This removes the layer lines and exposes the surface. After sanding the part, spray (or apply) the primer onto the part in two separate coats.

Once the model has dried, paint can be applied using a brush or spray. Masking techniques, for example using tape, can help with sharp color intersections.

Pros & Cons of Priming & Painting

Pros:

  • It enhances the look, adding color, as well as the feel of a product.
  • It gives a smooth, even finish.
  • It works on all FDM materials.
  • Parts can be painted with multiple colors.

Cons:

  • It is relatively time-consuming.
  • It is relatively costly due to equipment like paints, sprays, sandpaper, masks, and brushes.
  • Some amount of skill is necessary to achieve a smooth surface finish.

NOTE: Take proper safety precautions while spraying primer and paints. Carry out both tasks in a well-ventilated area or outdoors.

Technique #5: Hydro Dipping

Hydro dipping a plate in a dipping tank Source: Hydrodip

Hydro dipping is a relatively new technique to be used with 3D printed parts. Though typically used on a large scale for industrial products, small-scale hydro dipping can easily be applied to 3D printed parts for a great look.

Hydro dipping, also called as hydrographics, immersion printing, water transfer printing, or water transfer imaging, is a process of applying printed graphic designs to solid objects. This 3D printing post-processing technique is used on various materials like plastic, metal, wood, or glass.

Note that this is only used for enhancing the aesthetics of the object and does not change any dimensional properties nor the feel.

Pros & Cons of Hydro Dipping

Pros:

  • It enhances the look of the product.
  • It can be used to add a multi-colored or patterned design.
  • It works on all materials, including plastic, metal, wood, or glass.
  • It does not affect the dimensional accuracy of the product.

Cons:

  • It requires costly apparatus.
  • It requires skill to carry out the process.

Technique #6: Polishing

A very smooth PLA 3D print Source: Pierre Fontaine / ALL3DP

This 3D printing post-processing technique can be carried out with simple polishing tools, available at any local hardware store. Enthusiasts can buy polishing toolkits like the Dremel tools for getting a much-enhanced result.

Polishing should be carried out only after proper sanding. Polishing will enchance the effect of sanding, providing a much smoother finish.

Pros & Cons of Polishing

Pros:

  • It can be achieved using electric tools.
  • It’s a simple process.

Cons:

  • It released fine particles, which can be inhaled by the operator.
  • It require proper safety precautions.
  • A moderate amount of skill is required.

Technique #7: Electroplating

Electroplating is a great 3D printing post-processing option. It not only augments the look and feel of a part but also increases its strength.

On the other hand, only a few materials like ABS can be electroplated. Commonly used metals for electroplating are gold, silver, nickel, chrome, and copper.

Pros & Cons of Electroplating

Pros:

  • It significantly enhances the look, feel, and surface properties of a part.
  • It can increase the strength of a part.
  • Many outsourcing options exist for electroplating.

Cons:

  • Very few materials, which include ABS, can be electroplated.
  • It’s relatively expensive.
  • It’s a complex process.
  • It requires a lot of skill.

Technique #8: Gluing

Gluing PLA with ABS solvent cement Source: Tinkerine / YouTube

Multiple parts can be glued together to form a single part. This is mostly used in the case of large parts that cannot be 3D printed as a single piece due to dimensional constraints of the printer.

PLA is an example material that can easily be glued together using industrial bonding agents like Anabond.

Pros & Cons of Gluing

Pros:

  • It forms strong bonds between pieces.
  • It’s a simple process.
  • It’s relatively cheap.
  • It requires a minimal amount of skill.

Cons:

  • Very few materials, which include PLA, can be electroplated.
  • Glued parts are never as strong as solid parts.

Technique #9: Welding

Acetone melts the ABS, allowing it to fuse together Source: The Lucky Needle / YouTube

In this context, welding doesn’t refer to metal welding but the joining together of ABS parts using acetone. Acetone, as we already know, reacts chemically with ABS, melting it in the process. Using this property, we can apply light layers of acetone on two mating ABS parts, which are then held together to eventually form a bond.

Such welded bonds are fairly strong. The larger the surface area of the bond, the greater the strength of the bond.

Pros & Cons of Welding

Pros:

  • It forms strong bonds between parts.
  • It’s a simple process.
  • It’s relatively cheap.
  • Minimal skill is required to perform this operation

Cons:

  • Only ABS can be welded.
  • Welded parts are never as strong as solid parts.

Conclusion

A half-painted Yoshi Source: All3DP

We’ve now seen multiple 3D printing post-processing techniques by which we can achieve different results. Remember that post-processing is not only about the aesthetics of the object but also its feel, strength, and other properties. By employing the best-suited process for the specific application, users can reinvent their 3D prints.

License: The text of "FDM 3D Printing Post Processing – An Overview for Beginners" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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