Tolerance & Accuracy

The dimensional accuracy of 3D printed parts manufactured by 3D People

measuring the dimensional accuracy of a MJF part to qualify the 3D printing tolerance

3D printing tolerances overview

Tolerance is the permissible variation in dimensional accuracy. At 3D People, we use two types of 3D printing technologies, with multiple materials. Each material meets a standard of accuracy that we guarantee. The parts we produce through our online service will measure within our 3D printing tolerances.

Our Guaranteed Tolerances for your parts

  • 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    		 3D printing
    material    		 95% of
    printed parts    		 Guaranteed
    tolerance*    		 Guaranteed
    lower limit    		 Layer
    height
    Selective Laser Sintering (SLS) PA12 Nylon DATA-LOADING DATA-LOADING DATA-LOADING DATA-LOADING
    Selective Laser Sintering (SLS) PA12 Glass Filled Nylon DATA-LOADING DATA-LOADING DATA-LOADING DATA-LOADING
    Multi Jet Fusion (MJF) PA12 Nylon DATA-LOADING DATA-LOADING DATA-LOADING DATA-LOADING
    Multi Jet Fusion (MJF) Ultrasint TPU01 DATA-LOADING DATA-LOADING DATA-LOADING DATA-LOADING

    *We use a percentage to calculate the tolerance for a given dimension. For example, an SLS PA12 part with a measurement of 100mm has a permissible range of DATA-LOADING to DATA-LOADING.

Three factors contribute to the dimensional accuracy of 3D printed parts

1. Machine tolerance

Internal view of an SLS 3D printer with a roller distributing a fresh layer of nylon powder, part of the precision layer-by-layer printing process.

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

Close-up of cracked nylon powder surface inside an SLS 3D printer, showing warping caused by uneven cooling or thermal stress during the print process.

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

Parts undergoing automated depowdering inside a Dyemansion Powershot system, demonstrating the post-processing stage of SLS 3D printing

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.

First article inspection (FAI)

We offer First Article Inspection reports to verify key dimensions and qualify the accuracy of your parts. One part (or a set for large batches) is chosen at random from the first production run and measured to check dimensions against your drawing. The results are documented in a traceable report to demonstrate compliance with your specifications, including any regulatory or contractual requirements.

To request FAI for 3D printed parts, please provide a detailed technical drawing along with your order.
First Article Inspection report to evaluate the 3D printing tolerances
To request FAI for 3D printed parts, please provide a detailed technical drawing along with your order.

How to measure tolerances

Measure a digital dimension

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.

Calculate the permissable range

Calculate the permissible range for this dimension using the tolerance percentage for the corresponding 3D printing technology.

Measure your part

Measure the same dimension off of your 3D print. We recommend recording several measurements and using the average values.

Check if in range

Check to see if the measurement of the 3D printed part lies within the permissible range calculated in step 2.

Measure a digital dimension

A 3D CAD model displaying a measurement between two edges with an annotation showing a 25.000 mm distance.

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.

Calculate the permissable range

A tolerance range calculation showing a ±0.3% variation around a nominal 25 mm dimension, with results and the difference highlighted.

Calculate the permissible range for this dimension using the tolerance percentage for the corresponding 3D printing technology.

Measure your part

A hand using a digital caliper to measure the edge-to-edge distance of a white SLS nylon part, displaying a result of 25.01 mm

Measure the same dimension off of your 3D print. We recommend recording several measurements and using the average values.

Check if in range

An engineer analysing a 3D model of a part on their laptop, verifying dimensions of a part.

Check to see if the measurement of the 3D printed part lies within the permissible range calculated in step 2.

A 3D CAD model displaying a measurement between two edges with an annotation showing a 25.000 mm distance. A tolerance range calculation showing a ±0.3% variation around a nominal 25 mm dimension, with results and the difference highlighted. A hand using a digital caliper to measure the edge-to-edge distance of a white SLS nylon part, displaying a result of 25.01 mm An engineer analysing a 3D model of a part on their laptop, verifying dimensions of a part.

3D Printing Tolerances 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.