Understanding Accuracy, Precision, and Tolerance in 3D Printing

Accuracy, precision and tolerance mean different things with 3D printing. They define output, quality and capability in their own ways. Understanding what they mean individually will help you master 3D printing as a process.

In this article, we’ll explain in bite-sized chunks what accuracy, precision and tolerance mean in 3D printing and help you understand how they come together.

What is accuracy?

In 3D printing, accuracy refers to how close a printed model is to its design. A highly accurate model is identical to the one drawn in software. You can remember accuracy as the value that describes how close your print is to its digital design.

What is precision?

In 3D printing, precision refers to the repeatability of a measurement. This is a value that 3D printers have, rather than your model or CAD design. You can remember precision as the value that describes how reliable your 3D printer is.

What is tolerance?

In 3D printing, tolerance defines precision. A simple explanation for this is your 3D printer has tolerances. Your materials have tolerances. Your projects have tolerances. These define output and ultimately precision. You can remember tolerance as the limitations imposed by your 3D printer, your materials and by you.

Where does resolution factor in?

We thought you’d ask that. So, here’s a concise explanation. Layer resolution is a measurement of the layer height of each successive layer of material 3D printed. It is usually measured in microns. Contrary to belief, just because your 3D printer has a high resolution that doesn’t mean it will be accurate or precise. It simply means you have a higher tolerance to work with when it comes to printing fine detail.

What 3D printing technologies are most accurate and precise?

Now that you understand the differences between accuracy and precision in 3D printing, we’re able to get onto the good stuff and talk about hardware.

It’s important to keep in mind that 3D printing is an additive manufacturing process. This means that models are built up layer by layer, regardless of the technology. Or, if you like, they are ‘stacked’. However, there is a difference in the accuracy and precision between some technologies. This is because the process by which layers are formed affects the level of precision and ultimately model accuracy.

Stereolithography is considered to offer the most accurate 3D printing experience for desktop applications. With this technology, liquid resin is cured by a highly-precise laser to form each layer. The Formlabs Form 2 is an excellent example.

Fused Filament Fabrication 3D printers can also print accurate parts. But they have different tolerances or limitations. Chiefly, they can’t print as geometrically complex parts as SLA printers. Regardless, they are extremely precise. In our opinion, the standout Fused Filament Fabrication 3D printers on the market include the Zortrax M300 (pictured above) and Ultimaker 3.

Materials and their role in accuracy

We’ll finish up with a section about 3D printing materials.

These play a crucial role in the accuracy of your models. Every material has different mechanical properties – which can be thought of as tolerances.

A material or filament’s mechanical properties determine its dimensional stability and how likely it is to warp. They also determine how well it can show fine detail. For example, PLA is generally considered a better material than ABS for printing fine detail. This is because it prints at a lower temperature and is therefore less likely to warp.

Different materials offer different results. Your choice will play a role in the accuracy of your models. You’ll also find that switching between materials alters the precision of your models. This is because the tolerances have changed. This affects repeatability just the same as accuracy. So, as you can see, accuracy, precision and tolerance are linked.