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Keeping It Tolerable

How to Test and Improve Your 3D Printer’s Tolerances

Picture of Hironori Kondo
by Hironori Kondo
Nov 30, 2018

Whether it's CNC milling, bagging chips, or 3D printing, the machines involved have slight inconsistencies, producing parts of differing tolerances. Here, we'll dive into what tolerances are, and why they're important for 3D printing.

3D Printer Tolerance What Are Tolerances?

Tolerances dictate dimensional deviations.
Tolerances dictate dimensional deviations. Source: Formlabs

Tolerances describe how much deviation from a particular value is expected or acceptable. This can be in any context; one you might be familiar with is food packaging. A large container of nuts might be labeled as containing 1000 g +/- 5 g. The +/- 5 g is the tolerance, describing the amount of acceptable deviation.

In 3D printing, like any other manufacturing process, machines have specific tolerances. This means that prints may slightly deviate from the actual dimensions. A tighter tolerance indicates consistently higher dimensional accuracy.

3D Printer Tolerance Why Tolerances Matter

Tolerances are key for parts that must fit together.
Tolerances are key for parts that must fit together. Source: Sculpteo

3D printing tolerances are important when you create parts that must fit together. In particular, with FDM 3D printing, you need to watch out because tolerances tend to be loose.

If you have an idea of your printer’s tolerances, you can design parts with proper clearances in mind. Parts should be created with enough space between them to account for potential dimensional deviations.

Poor understanding of your 3D printer’s tolerances can cause parts to fit poorly or support structures to fully adhere to your prints.

Now that we understand why tolerances are important, let’s dive into how to test and improve your printer’s limits.

3D Printer Tolerance Testing for Tolerances

A dimensional accuracy test.
A dimensional accuracy test. Source: MatterHackers

To test for your 3D printer’s tolerances, start by properly calibrating your printer and its extruder. A helpful tool in this endeavor is a calibration cube.

When you’re ready, print out three to five of these dimensional accuracy tests or calibration cubes.

Measure each of the prints in the same place. Note the orientation of the model (indicated by the notch in the dimensional accuracy test and the large letters on the calibration cube). Record your measurements for each of the 3 directions (X, Y, and Z).

For each direction, subtract the smallest measurement from the largest measurement. This number is a good starting point for designing clearances. The tolerance of your printer will be +/- half of the clearance value.

Example: You might get 20.1, 20.0, and 19.9 mm for the calibration cube Y dimensions. Your clearance will be 20.1-19.9 = 0.2 mm, and your tolerance +/- 0.1 mm.

3D Printer Tolerance Directly Testing for Clearances

The Maker's Muse clearance test.
The Maker's Muse clearance test. Source: Sinterit

Alternatively, you can test directly for clearances. This is helpful if you’re only interested in fitting 3D printed parts with other 3D printed parts.

Angus Deveson from the Youtube channel Maker’s Muse has created very helpful clearance tests, one for free and one for $2. Just follow his guides for the free version or the improved $2 version.

With this tool, you can figure out how low you can set the clearances in your designs.

3D Printer Tolerance Improving Your Tolerances

Proper calibration and maintenance can improve tolerances.
Proper calibration and maintenance can improve tolerances. Source: 3D Hubs

There’s always room for growth. If you’re unsatisfied with your results, here are a few things you can try in order to improve your printer’s tolerances:

  • Check the motion components. Deteriorating components will make your printer less precise. Ensure that your printer’s belts are taught and that there is minimal wear on the rods or bearings. If not, tighten or replace the parts. Consult your printer manufacturer on how best to approach this.
  • Use better filament. Cheap filament usually has poor tolerances, which causes extrusion irregularities that can translate to irregular surfaces on your prints.
  • Properly calibrate your printer and your printer’s extruder before retesting for tolerances. If your tolerances vary with part size, it may be an indication of poor printer calibration. To accurately measure this variance, try using a calibration cube.

3D Printer Tolerance Going Further

With tolerances down, you're on your way to printing better mechanical parts!
With tolerances down, you're on your way to printing better mechanical parts! Source: Zmorph

Hopefully, this guide was helpful for testing and improving your 3D printer’s tolerances. With this locked down, you’re one step closer to producing precise, high-quality, mechanical parts!

Next, you’ll likely want to look into the best materials for your needs, and for FDM printing specifically, the filament choices that are available. Additionally, by learning how to make use of supports, you can achieve more complex mechanical structures.

Happy printing!

License: The text of "How to Test and Improve Your 3D Printer’s Tolerances" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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