Resolution, precision and dimensional accuracy describe different aspects of 3D printing performance. They should not be used interchangeably when evaluating a printing system or a printed part.
3Dresyns supplies scientific Instructions for Use (IFU) together with calibration files designed to measure and optimize dimensional accuracy in all three dimensions: x, y and z.
Key distinction: resolution describes printable feature detail, precision describes repeatability, and dimensional accuracy describes how closely printed dimensions reproduce the nominal dimensions of the digital design.
Definitions
- Resolution refers to the range of detail or minimum feature size that can be printed with fidelity. On the 3Dresyns flat coin, resolution can be evaluated by identifying the smallest concentric line that is printed clearly. The concentric features include engraved width and depth values ranging from 500 down to 2 microns, together with micron labels in relief.
- Precision refers to repeatability: the capability to reproduce the same dimensions repeatedly with limited variation between prints.
- Dimensional accuracy refers to how closely the printed x, y and z dimensions correspond to the theoretical x, y and z dimensions defined by the digital design.
A printing process can therefore be highly precise without being dimensionally accurate. Repeatedly producing the same dimensional deviation demonstrates repeatability, but not necessarily agreement with the nominal design dimensions.
How to measure dimensional accuracy with the flat coin
The 3Dresyns flat coin STL calibration file has a nominal thickness of 2 mm, excluding the raised micron text, and a nominal diameter of 25 mm in the xy plane.
Dimensional accuracy is evaluated by comparing the printed dimensions with these nominal dimensions.
Z-axis accuracy
Measure the real printed thickness and compare it with the nominal thickness of 2 mm.
XY accuracy
Measure the real printed diameter and compare it with the nominal diameter of 25 mm.
Worked examples: relative error and dimensional accuracy
Z-axis example
Nominal thickness: 2.00 mm
Measured printed thickness: 2.10 mm
Difference from nominal: 0.10 mm
Relative error = (0.10 / 2.00) × 100 = 5%
Dimensional inaccuracy = 5%
Dimensional accuracy = 95%
XY example
Nominal diameter: 25.00 mm
Measured printed diameter: 25.25 mm
Difference from nominal: 0.25 mm
Relative error = (0.25 / 25.00) × 100 = 1%
Dimensional inaccuracy = 1%
Dimensional accuracy = 99%
Resolution vs precision vs dimensional accuracy
The following visual summary illustrates the distinction between low and high resolution, precision and dimensional accuracy.
For the 3Dresyns flat coin calibration file, resolution is evaluated from the smallest concentric feature that can be printed cleanly and from the corresponding micron labels in relief.
Why three-dimensional calibration matters
Dimensional calibration should not be limited to the visibility of small xy features.
A printed part has dimensions in x, y and z. A printing system can reproduce fine xy details while still producing a systematic deviation in z thickness, or it can reproduce z dimensions correctly while producing dimensional deviations in the xy plane.
For this reason, resolution measurements and dimensional measurements provide complementary information.
Key takeaways
- Resolution describes the smallest feature size that can be printed with fidelity.
- Precision describes repeatability across multiple prints.
- Dimensional accuracy describes how closely the printed dimensions reproduce the nominal design dimensions in x, y and z.
- A highly precise printing process is not necessarily dimensionally accurate.
- Resolution and dimensional accuracy should be evaluated separately because reproducing a small feature does not by itself demonstrate correct overall dimensions.
- Proper calibration should evaluate all three spatial dimensions rather than relying exclusively on xy feature visibility.