AM Product Post-Processing & Quality Control

The surface finish and treatments play a pivotal role in determining the final appearance, feel, and sometimes even the function of the 3D printed object. Choosing the right finish or treatment can greatly expand the range of applications and longevity of AM-produced parts. Some examples of ways the surface finish of additively-produced parts can be affected include:

• Smoothing Plastic 3D Prints:

  1. Chemical Smoothing: For materials like ABS, a vapor bath (typically using acetone) is utilized. The part is exposed to the vapor, causing the outer layer of the print to slightly dissolve, leading to a smoother finish.

  2. Mechanical Sanding: Using a progression of sandpaper with varying grits, the printed part's surface is manually sanded to achieve a smoother finish. This method can be labor-intensive but allows for precise control over the final appearance.

  3. Thermal Processes: Some methods involve carefully controlled heating of the print surface, causing a slight melting or reflowing that can reduce layer lines and irregularities.

•  Painting/Coating:

  1. Primer Application: To ensure better adhesion and a smoother surface, a primer might be applied to the 3D printed object before painting.

  2. Spray Painting: Once primed, spray paints are often used to give a uniform, colored finish to 3D printed parts. This not only enhances appearance but can also provide additional protection against UV light or other environmental factors.

  3. Specialized Coatings: Depending on the application, the 3D printed part may receive a coating for specific purposes, such as waterproofing, UV resistance, or added strength.

• Electro-Plating:

  1. Surface Preparation: Before plating, the 3D printed object's surface must be cleaned and made conductive, often through a conductive paint or a thin layer of graphite.

  2. Bath & Current Application: The part is submerged in a solution containing metal ions. When an electric current is applied, these metal ions are reduced and deposit onto the part's surface, building up a metal layer.

  3. Benefits: Electro-plating can drastically enhance a 3D printed part's properties. It can increase strength, wear resistance, electrical conductivity, and even provide a shiny or decorative finish, imitating the appearance of solid metal objects.

Quality control (QC) in additive manufacturing is vital to ensure the reliability, functionality, and safety of printed parts. As AM finds increasing applications in critical sectors such as aerospace, medical, and automotive, stringent QC protocols are essential. Some ways that parts made with AM are often inspected include:

• Layer Inspection:

  1. Description: As AM builds parts layer-by-layer, it's crucial to inspect each layer for potential issues.

  2. Methods: High-resolution cameras and sensors monitor the printing process, capturing real-time images and data to detect any anomalies, like warping or voids.

  3. Importance: Early detection of defects can save material, time, and ensure the structural integrity of the final product.

• Dimensional Accuracy:

  1. Description: Checking the physical dimensions of the printed part against the original design specifications.

  2. Methods: Tools like calipers, micrometers, and more advanced methods such as laser scanners or Coordinate Measuring Machines (CMM) are used.

  3. Importance: Ensures that the final part will fit and function as intended, especially vital for parts that interface with other components.

• Material Properties Testing:

  1. Description: Verifying that the printed part possesses the intended mechanical, thermal, and chemical properties.

  2. Methods: Tests can include tensile testing, hardness testing, fatigue testing, and thermal analysis, among others.

  3. Importance: Ensures that the part can withstand the conditions and stresses of its intended application.

• Porosity & Internal Structure Analysis:

  1. Description: AM parts can sometimes have internal voids or porosities that weaken the structure.

  2. Methods: X-ray computed tomography (CT) scanning offers a non-destructive method to visualize and assess the internal structure of printed parts.

  3. Importance: Identifying and addressing internal defects is critical for parts used in high-stress or critical applications, like aerospace components.