Reaching tight tolerances is a challenge for most 3D printers. Instead of fighting your printer’s accuracy, work around it by utilizing post-processing. 

In manufacturing, most processes are divided into “subtractive” or “additive” methods. For example, when you cut wood to a length or machine an aluminum block to specific dimensions, you “subtract” material, until you reach a desired measurement. However, when you manufacture parts using a 3D printer, you “add” material, until you reach a desired size. 

Today, 3D printing has made huge leaps in accuracy, as an additive manufacturing method; but it isn’t quite perfect -- yet. As of 2019, most 3D printers create a “near-net-shape” part, to almost meet design specifications. Of course, many subtractive manufacturing methods also create “near-net-shape” parts, but these methods (CNC milling, laser-cutting) have had decades to evolve. They may create more accurate net-shape parts, since 3D printing is in its adolescent stages.

If you’re considering 3D printing for your manufacturing process, it is crucial to remember that 3D printing is accurate to a point. So, if you need critical parts that fit within tight tolerances, post-processing is a required, essential step.

To post-process a part, use a combination of the following four methods:

  • Removal of Support Structures
    • Take off supports either by hand or with pliers. For greater smoothness, use sanders/sanding paper
    • Pro-Tip: Check out this Vision Miner video on how to shorten post-processing by designing with minimal support structures.
  • Surface Smoothing (Varies based on material durability)
    • For low-temperature/less-durable materials (ABS, PLA, etc)
      • Coat, dip, or brush ABS parts
      • Light sanding
      • Vibratory Tumblers
    • For high-temperature/more-durable materials (PEEK, PEI, etc)
      • More abrasive sanding
      • Machining net-shape to specification via milling
      • Vibratory Tumblers
      • CNC Machine-finishing
  • Surface Coating
    • Similar to treating rough cuts of wood: paint, epoxy-dip, or coat part with a desired chemical, to fill-in surface ridges.
  • Assembly-based Design
    • Print your part into multiple sections that can be assembled using bonding agents, fasteners, glue, or built-in assemblage designs like pins and holes.

To use a manufacturing method like 3D printing to its fullest extent, we need to understand both its strengths and its limitations. By acknowledging FDM’s near-net-shape quality, you can design parts that are less expensive and as strong as the milled or routed metal equivalent.e