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[Krie Taakur]

Tutorial: Smoothing 3D Print Using Polyester Resin
Co-Authors: Ori'Kotir; Krie Taakur
Edited by: MMCC Education Team

This tutorial will walk you through the smoothing of the surface of a 3D print. In this example we are using an arm band printed out of PLA plastic.

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3D Print Finishing Made Easy

Materials and Tools Needed

• Traditional sandpaper (60 - 150) grits
  
• Wet/Dry sandpaper (400) grit
  
• Abrasive pad (fine)
  
• Polyester resin & Catalyst
  
• Autobody filler (Bondo) & Catalyst
  
• Paper mixing cups
  
• Mixing sticks
  
• Bristle brushes
  
• Filler primer
  
• Basins for water
  
• Gloves
  
• Ventilated area
  
• Respirator
  

Set up the work space
In this case we set up a trestle using two mixing sticks and clay to keep the part off of the table to so it would not be glued down by the resin.

Setting up the work space.


Prep the Surface
Lightly sand the surface of the print with 60 grit (the goal is to remove any loose pieces or strands of plastic)

Mix the Polyester Resin
Mix polyester resin (polyester resin is occasionally called “Fiberglass resin”) and autobody filler (occasionally referred to as “Bondo”) in a 50/50 volume ratio along with the appropriate catalyst (normally 15 drops per oz for polyester resin and enough cream hardener to get a salmon pink color).

Mixing the polyester resin.



Apply the Polyester Resin
Brush the mixed resin onto the surface of the print. Be mindful of deep areas or resin pooling. You just need enough to fill the gaps in the print lines.

Applying the polyester resin.



Dry Sanding
Sand the surface with 60 grit working up to the 150 grit. Your goal is to smooth the surface not to remove all of the resin you added.

Dry sanding the polyester resin.



Wet Sanding
Set up a basin with water and use the 400 grit wet/dry sandpaper. Wet the print and the paper and lightly and gently sand the surface in a circular pattern. Wet sanding keeps the paper from clogging and the water acts as a lubricant and to cool the surface as you sand.

Wet sanding the polyester resin.



Priming Prep
Dry the piece and set it up for priming. Fill a small container with hot water. Shake the filler primer can per the directions on the label (normally 1-2 minutes)
Then place the can of paint into the hot water for 3-5 min. This will thin the paint slightly and increase the pressure in the can and give you the finest even spray possible.

Preparing the primer.


Priming
Using a gloved hand if possible hold to piece about 15" away from the spray can. Lightly spray a thin coat of primer on the piece. Start spraying off of the piece and move the can and spray paint path over the piece and stop the spray. Never start or stop the spray path on the piece directly. Only move the paint over the piece.
(General guide is 50% of the spray should be on the object being painted)
Set the piece down to dry.
Repeat the above process a few more times.

Priming.


Finishing
After it is thoroughly dry lightly smooth or buff it using a fine abrasive pad.
Often this is all that is needed to smooth a printed piece.

Finishing.



Final Tips
In some cases you will need to do cosmetic work or fill small pits or flaws in the print. This is best done with autobody filler and glazing putty. This will be covered in additional tutorials.

Raw print vs. finished surface.


--MMCC Education Team--