How to Paint FDM Parts

There are many reasons for coating FDM parts. These include UV protection, sealing, shielding, or surface modification, but painting FDM parts for an aesthetically pleasing finish is the most common. Painting brings a product to life by adding depth, contrast and character. This is true for concept models, marketing samples, and finished goods. For product development and many production applications, paint completes the desired look and feel. With a little know-how and a touch of patience, models, prototypes, and parts can look like production parts.

The following instructions are for creating top-quality painted parts. For applications that do not require this level of finishing, skip any unneeded steps. A good paint finish traditionally starts with sanding and filling.

  1. Step 1: Required Materials

    • Sandpaper: 220- to 800-grit wet/dry
    • Filler: 3M Acryl-Green Spot Putty and/or Acryl-Red Glazing Putty
    • Degreaser: PPG Acryli-Clean DX330
    • Sandable primer: PlastiKote T235
    • Paint:

    -Spray can enamel: Dupli-Color®, Rust-Oleum®, Krylon®, or Testors® Model MasterT

    -Spray gun: Sherwin-Williams®, Polane® T-plus, Cardinal Industrial Finishes (Pantone®) or PPG®

    • Clear coat:

    -Acrylic lacquer

    -Polyurethane: PPG Deltron® Ultra Velocity Clearcoat (DC2000, DC3000 or DC4000)

  2. Step 2: Options

    Paint Options

    • Fillers: Used for surface preparation when moderate to severe surface filling is required. Use filler when the part has excessive layering or when there are surface voids that primer will not fill.

    • Primers: Used for surface preparation when minimal surface filling is required, or to improve paint adhesion.

    • Paints: Used to provide the desired color, texture, and luster.

    Application Methods

    • Spray Can: Spray paints are easy to use and do not require additional equipment (e.g. spray gun). With a good quality enamel paint and a well- ventilated space, anyone can paint FDM parts. By using the proper technique—thin coats, steady sweeps across the part, and proper distance— the painted part will have a nice appearance.

    • Spray Gun: For a professional paint job, a spray gun and paint booth are needed (Figure 2). In the hands of an experienced painter, the spray gun’s precise control combined with a good quality enamel paint will produce exceptional results.

    Clear Coat Options

    • Acrylic lacquer: May contain solvents that will react with the underlying plastic.

    • Polyurethane: Hard, durable clear coat that offers greater protection than acrylic lacquers.

  3. Step 3: 1. Removing Supports

    STEP 1: Remove support structures (Figure 3)

    STEP 2: If a part had soluble supports, rinse thoroughly in tap water to clean the part and remove WaterWorksTM detergent. Then, allow part to dry.

  4. Step 4: 2. Preparing Surfaces

    STEP 1: Lightly sand with 220-grit sandpaper

    STEP 2: Remove any dust and debris

    STEP 3: (Optional) For an ABS part, either dip it in a methylene chloride solution, such as IPS Weld-On 4®, or vapor smooth it in a Finishing Touch® Smoothing Station (Figure 4).

    STEP 4: Fill voids between extrusion path layers with a filler such as 3MTM Acryl-Green Spot Putty (Figure 5). Spread the filler to cover depressions. Avoid applying overly thick coats.

    TIP: A light coating of fast-drying primer will fill small voids and reveal minor imperfections. Although it adds time, many find that this makes the task of filling and sanding easier by drawing attention to the areas that need work. Ensure primer has completely dried before continuing the preparation process (Figure 6).

    STEP 5: Allow the filler to dry, following manufacturer's recommendations

    STEP 6: Inspect the part. If imperfections remain, return to Step 3. Repeat as needed.

    STEP 7: Sand all surfaces with 220-grit sandpaper until they are visibly smooth (Figure 7). Then, sand all surfaces with 320- to 400-grit sandpaper. This is a good level of smoothness for most finish types.

    STEP 8: Remove dust and debris.

    STEP 9: Clean the part with a degreaser, such as PPG Acryli-Clean® DX330, to remove additional oil, dirt and dust.

  5. Step 5: 3. Prime Surfaces

    STEP 1: Spray a light coat of primer on the part. Avoid heavy coats as they will drop and puddle (Figure 8).

    STEP 2: Allow primer to dry, typically for 2 to 24 hours, following manufacturer’s instructions.

    STEP 3: Apply a second primer coat and allow it to dry.

    STEP 4: Sand primed surfaces. If the finished part requires a matte or textured finish, sand the part with 320- or 400-grit wet/dry sandpaper until smooth. If the finished part requires a gloss finish, begin with 320- or 400-grit wet/dry sandpaper and progress to finer grits concluding with 600- to 800-grit wet/dry sandpaper. Surfaces should have a polished appearance when complete.

    STEP 5: Remove dust and debris.

    STEP 6: Clean the part with a degreaser and allow the part to dry completely.

  6. Step 6: 4. Paint Part

    STEP 1: Adjust the spray gun’s pressure and flow rates to lay down a thin, even coat of paint, or prepare and test the spray can.

    STEP 2: Apply a light coat of paint to prevent dripping or puddling (Figure 9)

    STEP 3: Allow paint to dry, typically for 15 to 45 minutes, following manufacturer's recommendations.

    STEP 4: Apply a second coat of paint and allow it to dry. Repeat as necessary.

    STEP 5: Allow paint to dry completely following the manufacturer’s recommendations.

    STEP 6: Apply a clear coat to protect the painted finish. As with painting, apply two thin coats, allowing the first coat to dry before applying the second.

    STEP 7: Painting procedure complete.