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Contents:

Understanding 3D Printing tolerances and accuracy

Key takeaways

3D printing tolerances define the acceptable variation between your CAD model and the final manufactured part.
Most Sculpteo materials use a combination of a percentage-based tolerance and a minimum tolerance.
Small features are governed by the minimum tolerance, while larger dimensions follow the percentage tolerance.
Dimensional accuracy varies depending on the technology, material, part geometry, and build orientation.
Larger parts naturally experience greater dimensional variation than smaller parts.
For assemblies and mating parts, designers should always include adequate clearances and tolerances during the design phase.
If a dimension is critical, secondary machining operations may be required to achieve tighter tolerances.

Introduction

When ordering a 3D printed part, one of the most important specifications to understand is dimensional accuracy. Whether you are designing a prototype, a functional assembly, or an end-use component, knowing what tolerance to expect helps ensure your part performs as intended.

However, dimensional tolerances are often misunderstood. What does a specification such as ±0.3% (minimum ±0.3 mm) actually mean? Why do small parts and large parts behave differently? And how do tolerances vary between additive manufacturing technologies?

In this guide, we explain how dimensional tolerances work and provide a complete overview of the tolerances available across Sculpteo’s manufacturing technologies.

What is tolerance / accuracy?

A tolerance defines the acceptable variation between the dimension specified in your CAD model and the dimension of the manufactured part.

For example, if a dimension is designed at 100 mm and the manufacturing tolerance is ±0.3 mm, the final dimension may measure anywhere between:

99.7 mm
100.3 mm

while still remaining within specification.

No manufacturing process can produce parts with perfect dimensional accuracy. Small variations occur due to machine precision, material behavior, thermal shrinkage, and post-processing operations.

Understanding percentage tolerances and minimum tolerances

Many additive manufacturing materials use a specification similar to:

±0.3% (minimum ±0.3 mm)

This means two tolerance rules coexist:

A percentage-based tolerance applied to larger dimensions.
A minimum tolerance applied to smaller dimensions.

The larger value always applies.

Example 1: Small feature

CAD dimension: 10 mm

Percentage tolerance:

10 × 0.3% = 0.03 mm

Since 0.03 mm is smaller than the minimum tolerance of 0.3 mm, the applicable tolerance becomes:

±0.3 mm

Final dimension range:

9.7 mm
10.3 mm

Example 2: Medium feature

CAD dimension: 100 mm

Percentage tolerance:

100 × 0.3% = 0.3 mm

Applicable tolerance:

±0.3 mm

Final dimension range:

99.7 mm
100.3 mm

Example 3: Large feature

CAD dimension: 300 mm
Percentage tolerance:

300 × 0.3% = 0.9 mm

Since 0.9 mm exceeds the minimum tolerance, the applicable tolerance becomes:

±0.9 mm

Final dimension range:

299.1 mm
300.9 mm

Visualizing how tolerances scale

As dimensions increase, tolerance values increase proportionally.

Nominal Dimension	0.3% Tolerance	Applicable Tolerance
10 mm	±0.03 mm	±0.3 mm
25 mm	±0.075 mm	±0.3 mm
50 mm	±0.15 mm	±0.3 mm
100 mm	±0.3 mm	±0.3 mm
200 mm	±0.6 mm	±0.6 mm
500 mm	±1.5 mm	±1.5 mm

This is why larger parts naturally exhibit larger dimensional variations than smaller parts.

Why do tolerances exist in 3D Printing?

Several factors influence dimensional accuracy:

Material shrinkage during cooling
Layer-by-layer manufacturing effects
Build orientation
Part geometry
Wall thickness
Internal stresses
Post-processing operations such as polishing, dyeing, vapor smoothing, or machining

For this reason, tolerances should be considered during the design phase, especially when creating mating components or mechanical assemblies.

Looking for the most accurate 3D Printing material?

Not all 3D printing materials offer the same dimensional accuracy. While some materials achieve tolerances as tight as ±0.3%, others may have different tolerances depending on the manufacturing process, material behavior, and part orientation.

If dimensional precision is a critical requirement for your application, we recommend comparing the technical specifications of each material before placing your order.

Our Material comparison guide allows you to compare layer thickness, build size, tolerances, mechanical properties, and key advantages across all available Sculpteo materials, helping you select the best option for your project.

Design recommendations

When designing parts for additive manufacturing:

Do not design press fits based solely on nominal dimensions.
Always account for manufacturing tolerances.
Add appropriate clearances for moving assemblies.
Consider machining or secondary operations for critical dimensions.
Contact our team if specific dimensions require tighter tolerances.

Conclusion

Dimensional tolerance is a critical parameter in additive manufacturing. Understanding the difference between percentage-based tolerances and minimum tolerances helps predict how your part will behave at different scales.

Small dimensions are generally governed by the minimum tolerance, while larger dimensions follow the percentage tolerance specified for the material. By taking these factors into account during design, engineers can achieve more reliable and predictable results from 3D printing.