How to reinforce 3d printed parts with fiberglass - The 3D Printer Guy

How to reinforce 3d printed parts with fiberglass

Though some 3D printing filaments are already made with durability in mind, here's a technique that can add some sturdiness and durability to our good-old ABS parts.

Strengthening parts with this post processing technique can be a good idea for parts that will be used outdoors and will be subject to weather elements. Also, it is recommended for parts that will be under physical strain. Some examples are: propeller blades, canoe paddles, cases, handles.

The idea is simple: print a part as you normally would, and then apply a fiberglass coating.

Here are the steps and some example photos of the technique I just described.


  • Your 3d printer with ABS filament (other filaments may work as well)
  • Fiberglass kit, consisting on resin, hardener (catalyst) and fiberglass fabric. You can find these in ebay searching for the term "fiberglass repair kits"
  • Protective latex gloves (sometimes included in the fiberglass kit)
  • Paint brush  (sometimes included in the fiberglass kit)
  • Alcohol or acetone (usually not included in the kits, this is used to clean any unwanted or spilled resin)


 1. Print your part using ABS

Since we are aiming for robustness, try printing with a nice infill (50% to 70% sounds reasonable).

Layer height should not be a concern. The coating will cover any and all small details in the print, so no need to go HI-RES here, if you have a 0.4mm nozzle then go for a 0.25mm layer height.

For increased strength, try printing with thick shell (perimeter) and bottom/top. A thickness of 5 or 5 times the nozzle size should be fine.

Don't be shy to print support material as needed, just be sure to remove it after the print is done.

Part being printed (the square borders is only the support material)


2. Basic post-processing

Once the part is printed, let it cool and remove it from the build plate.

Remove all support material (if any).

Apply some light sandpaper just to get a more rough and non-slippery surface.

 Printed part with support material already removed and some light sandpaper already applied.​



3. Apply the fiberglass coating

Put on the gloves and prepare the fiberglass resin according to the kit's instructions. Usually this process consists of putting the required amount of resin in a container and then adding a little bit of hardener (catalyst) and stir everything with a disposable stick.

Use scissors to cut pieces of the fiberglass fabric (so it is easier to handle)

Use the paint brush to apply an initial coat of prepared resin over the piece of fabric.

Push the piece of fabric against the printed part so the fabric is "glued" to the part by the resin. Use your hands to mold the layer of fabric to the shape of the part.

Apply a 2nd layer of resin on top of the fabric.

Repeat the process until the part has 2 or 3 layers of fabric and the last layer is covered by resin.

Allow it to dry. Depending on the specific kit and amount of layers, the part can be dry and hard in just a few hours, however, read the instructions of the fiberglass manufacturer since some recommend to wait longer.


4. Additional processing

Optional: after the part hardens, you could use a power-tool to grind  any excess fiberglass or to smooth the surface of the part, of you decide to do this, be sure to wear breathing and eye protection when grinding fiberglass.

Recommended: apply paint!! fiberglass can be ugly, if you want your part to look good, it may be a good idea to apply some color. Traditionally, fiberglass parts are coated with "gel coat", a wax rich polyester resin, but many other common paints can also be used.


5. Use the reinforced part.

Go ahead and try the part. The reinforced fiberglass coating will let the part sustain heavy exposure to weather and physical stress

Part already covered with a few layers of fiberglass and mounted on a boat's motor. 

Notice that this part has not been grinned nor painted and looks fairly ugly.


3D printing is a fairly new technique and usually there are no "standard solutions" for industry-specific applications, so there is still a lot of trial and error experimentation among hobbyists and professionals. If you are the DIY kind of person, I encourage you to try this technique and even send us an email with pictures of your results so we can showcase them!

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