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Picture of 3D Print Smoothing - Polymer Clay

Fused-Filament Fabrication (FFF) or Fused-Deposition Modeling (FDM) -"3D Printing"- create amazing parts, but generally with visible layers. There are two main methods for smoothing those layers to obtain an injection-molded plastic look: chemical-smoothing or sanding. Chemical-smoothing is dangerous as it involves toxic and highly flammable chemicals, and sanding takes patience and well-toned hand muscles or skill with a Dremel.

As an alternative to these two methods, I looked to polymer clay as another form of smoothing.

My conclusion:

Applying the clay takes patience and a little skill (with the help of "tools"). Depending on your level of sanding skill, applying the clay can take longer or shorter than sanding. With regards to toxicity, I'd say it's safer than chemical smoothing, but I still suggest using ventilation and a non-food-used oven when baking it.

A major downside is the tendency for the part to shrink during the baking process. This has to be taken into consideration when creating fitted parts. The upside, is that this process can aid in attaching separate parts together permanently and can fix defects that the other two process cannot.

For me, this is my preferred method for smoothing, as I can apply the clay while watching TV and not have to worry about concentrating too hard (whereas with a Dremel, you need to pay close attention to what you are doing). If I get better at sanding, I may decide that applying clay is too long of a process.

Amendment: Because Polymer Clay is a polymer (plastic), it cannot properly harden at a lower baking temperature than given in the instructions. This means that this technique can only be used for ABS, or other higher extrusion temp materials.

The files used to illustrate the process can be found here:

Golbat Wall Sconce by WeeksB (me)

Pumpkisaur Pokemon by chicagolandgeeks

Bulbasaur Pumpkin Tealight Remix by Blackhartfilms

Step 1: 3D Print the Model

Picture of 3D Print the Model

Print out your desired model. This can be done on your own printer, a friend's printer, or you could use one of the many services to get files printed for you. Assemble the parts, if necessary, using your preferred form of bonding.

Depending on the file, and the skill of the printer operator, you may find defects in your print.

Certain defects and unwanted appearances can be solved by the polymer clay smoothing method:

  • Layer lines (shown on the printed wing and assembled Golbat)
  • Sagging (shown on the jack-o-lantern)
  • Pitting
  • Seam lines
  • Assembly gaps
  • Some incomplete or broken parts (this depends on your skills at molding clay)

Note: Warped, distorted, or severely incomplete parts might be able to be "fixed" with the clay, but will likely require strong clay modeling skills and rely on sections made of solid clay.

Dawsie5 months ago
I have been using polymer clay for years, Just a few tips to help :-)
1. When baking at a lower temp that has been recommended you have to double your baking time. If you don’t you run the risk of braking your pieces due to their not being fully cured.
2. Always cover you work with a aluminium foil like a tent and placed on a baking tray, this will stop your parts getting scorched by an oven that fluctuates while baking all old ovens do this. (not sure about the new modern ovens.) By covering your work you stop the out gassing of the oils coating the oven it will only coat the foil that can be kept for repeated use.
3. When sanding polymer clay always use wet/dry sand paper used wet with a little dishwashing liquid this will help with the drag on the sandpaper and will give you a cleaner smother finish.
4. Don’t use cheap unknown brands of polymer clay they do not always give good results that you are looking for.
5. Clay should always be preconditioned before using this helps with activating the oils within the clay
6. Try using baby oil it will help with softening the clay and will make it easier to smooth the clay it will not hurt or change the baking times of the clay but it will make it nice and soft and easier on your hands and fingers.
7. If there are fingerprints on the clay using a Cotten bud and baby oil this will help wipe away all marks.
8. Always use water based varnish anything else will over time damage the polymer clay even with acrylic paint between it and the clay. Never use clear nail polish as a way to varnish it will damage your work over time. A few people have done this and have lost their work because of it. UV Gel polish is fine and safe to use.

I hope this helps you and anyone else who are looking into using 3D printing :-)
Bethany Weeks (author)  Dawsie5 months ago
Fantastic! Thank you very much for sharing your polymer clay modeling tips.
:-) Your very welcome Bethan, so much was taught to me when I first started down the polymer clay road it’s only fair to pass on what was taught to me :-)
I love the way these look when you're done! Looks like a very nice method :)
Bethany Weeks (author)  Penolopy Bulnick5 months ago
Thank you! I prefer it, but the clay application, does seem to take a lot of time. Mainly, from my fingers getting tired and needing a break.