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