TOLERANCE & ACCURACY
The dimensional accuracy of 3D printed parts manufactured by 3D People
SUMMARY:
Tolerance is the permissible variation in dimensional accuracy. At 3D People, we use two types of 3D printing technologies, each one meeting a standard of accuracy. The parts we produce through our online service will measure within our 3D printing tolerances. The parts we produce through our online service will measure within our 3D printing tolerances.
DIMENSIONAL ACCURACY OF 3D PRINTED PARTS
Three factors contribute to the precision and accuracy of 3D printed parts.
1. Machine Tolerance
All 3D printers have variations in accuracy determined by their engineering and construction. The many moving components must remain calibrated to one another for accurate results. Tolerances provided by the machine manufacturers give us guidelines on what to expect. However, these only apply to designs optimised for 3D printing with their technology.
2. Material Shrinkage
3D printed polymers shrink as they are cooled during the printing process. Elements of a part that shrink at a different rate cause internal stresses that can affect the dimensional accuracy. Several variables cause uneven shrinkage such as part geometry, heat distribution, printer settings, orientation and cooling rates.
3. Post Processing
3D printed parts undergo additional processes after removal from the machines. Cleaning of the surfaces, removal of support material and other finishing techniques can alter the external dimensions. An optimised design considers the post-processing requirements for the printing technology and minimises its impact on the accuracy of its surfaces and features.
3D PRINTING TOLERANCES
The value of tolerance for each of our 3D printing technologies are a result of 3D printing and measuring many thousands of custom components. The vast majority of parts we produce are considerably more accurate than our guaranteed tolerances. The reason we cannot guarantee more accurate tolerances as some dimensionally challenging geometries are prone to warping.
| 3D Printing Technology | 95% of printed parts | Guaranteed Tolerance* | Guaranteed Lower Limit | Layer Height |
|---|---|---|---|---|
| Selective Laser Sintering (SLS) | ± 0.15% | ± 0.3% | ± 0.15 mm | 100 microns |
| Multi Jet Fusion (MJF) | ± 0.2% | ± 0.3% | ± 0.25 mm | 80 microns |
*We use a percentage to calculate the tolerance for a given dimension. For example, an SLS 3D print with a measurement of 100 mm has a permissible range of 99.7 mm to 100.3 mm
HOW TO MEASURE TOLERANCES
We use highly accurate measuring equipment to record the dimensions of the 3D printed parts and check them against their corresponding 3D file. Any measurement that lies outside of the acceptable range out of tolerance.
Step 1.
Measure a dimension from the 3D file in a 3D CAD program. It is best to use the exported mesh file as opposed to the original CAD model.
Step 2.
Calculate the permissible range for this dimension using the tolerance percentage for the corresponding 3D printing technology.
Step 3.
Measure the same dimension off of your 3D print. We recommend recording several measurements and using the average values.
Step 4.
Check to see if the measurement of the 3D printed part lies within the permissible range calculated in step 2.
FAQ:
+ What is Guaranteed Tolerance for 3D printing?
Guaranteed tolerance is the maximum permissible deviation in the dimensions of a printed part from its design. It helps in ensuring the consistency and quality of printed components.
+ What causes dimensional inaccuracy in 3D printing?
A common cause for dimensional inaccuracy is uneven material shrinkage during the cooling process, causing internal stresses in the printed part. This may affect its dimensional accuracy and overall integrity, especially for large flat parts.
+ Why is machine tolerance important in 3D printing?
Machine tolerance refers to the inherent variations in accuracy determined by a printer's engineering and construction. Ensuring proper calibration among the moving components of the printer is essential for precise results.
+ How does post-processing 3D prints impact the dimensional accuracy?
Post-processing, such as surface cleaning or support material removal, can alter a part's external dimensions. A well-optimized design will consider these post-print requirements, helping to maintain accuracy.
+ Why might some geometries be more prone to warping?
Certain complex or thin geometries might not have uniform cooling or may experience uneven stress distribution during the printing process, making them more susceptible to warping.
+ Why is tolerance expressed as a percentage?
Expressing tolerance as a percentage allows us to calculate permissible variations relative to the actual dimension of a part. This way, larger parts have a proportionally larger tolerance range compared to smaller parts.
+ How do you measure and verify the tolerances?
We employ high-precision measuring tools to record the dimensions of the 3D printed parts, then cross-check against the original 3D file's dimensions. This ensures the parts meet our specified tolerances.
+ If I have concerns about my design's compatibility with the chosen 3D printing method, can I discuss it with your team?
Absolutely! We encourage clients to reach out with any specific requirements or concerns. Our team can provide insights and suggestions to ensure optimal print results.