Hubs is now Protolabs Network. Find out more

Get instant quote

3D printing STL files: A step-by-step guide

Learn how to avoid low quality 3D prints or unnecessarily large files by exporting your STL file in the correct resolution.

3D Printing STL files: A step-by-step guide

Introduction

The STL (Standard Triangle Language) is the industry standard file type for 3D Printing. It uses a series of triangles to represent the surfaces of a solid model. All modern CAD (Computer Aided Design) software allow you to export their native file format into STL. The 3D model is then converted into machine language (G-code) through a process called “slicing” and is ready to print.

This article will teach you the basic steps you need to follow to correctly export your models for 3D printing.

Curious about the cost of 3D printing your STL files?

Upload your parts

Step 1. Understand the STL resolution

The STL file format uses a series of linked triangles to recreate the surface geometry of a solid model. When you increase the resolution, more triangles will be used, approximating the surfaces of the 3D model better, but also increasing the size of the STL file.

A sphere rendered in three different resolutions in MeshMixer

If you export in too low of a resolution, the model will have visible triangles on its surface when it is printed. Most of the times this is undesirable, but it can be exploited to create “low-poly” models with a digital look.

Increasing the resolution above a certain point is also not recommended, as it brings no additional benefit: very fine details cannot be 3D printed, so the size of the file will be unnecessarily increased, making it more difficult to handle and process.

A low resolution sphere: The triangles are affecting the shape

Step 2. Choose the right exporting parameters

You can change the resolution of your STL files by altering the tolerance in your CAD software. When unsure, selecting the “high” preset is the safest option for generating an STL file that is suitable for 3D printing.

Each CAD package has a different way of specifying the STL resolution, but most use two main parameters: chord height and angle.

The chord height is the maximum distance that your software will allow between the surface of the original 3D model and the surface of the STL file. Using a smaller chord height will help represent more accurate the curvature of a surface.

The recommended value for the chord height is 1/20th of the 3D printing layer thickness and never below 0.001 mm (1 micron). This will always result in an STL file with ideal accuracy for most 3D printing applications. Exporting in a smaller tolerance will not have any effect in the quality of your print, as most common 3D printers are not able to reproduce such a high level of detail.

A visual illustration of chord height

The angular tolerance limits the angle between the normals of adjacent triangles. The default setting is often 15 degrees. Some software also specify this tolerance as a value between 0 and 1. Unless a higher setting is necessary to achieve smoother surfaces, the default value of 15 degrees (or 0) is recommended.

A visual illustration of angular tolerance

Step 3. Export STL files from your CAD software

All CAD software have their own way to export STL files. Use the following table as a quick reference:

Software Description
Solidworks
File > Save As... Set Save As... file type to STL Options > Resolution > Fine (or Custom) > OK
3DS Max
3DS Max Application Menu > Export > StereoLitho (*.STL)
AutoCAD
Output > Send panel > Export At the Command prompt, enter export. In the Export Data dialog box, enter a filename. Under Files of Type, select Lithography (*.stl) and click Save. Select one or more solid objects. Note: The XYZ coordinates of all objects must be above zero. The file extension .stl is automatically appended to the file name.
Fusion 360
File > 3D Print Under Refinement / Refinement options, select export settings. Output > untick “Send to 3D Print Utility” > OK > Save
Inventor
File > Print > 3D Print Preview Save Copy As... (top left of window) > Save
Onshape
Right click on [Part Name] on bottom right > Export Under Format, select STL. Specify model units. Select export settings.
PTC Creo
File > Save As... > Save a Copy Change Type to Stereolithography (*.stl). Click OK > a new Export STL dialog will open. Under Deviation Control, change export settings.
Rhino
File > Save As… In the Save As... box, select Stereolithography [*.stl].
Sketchup
Download Sketchup to DXF or STL plugin. Start Sketchup. Tools > Export to DXF or STL
Solid Edge
File > Save As... Set Save As... file type to STL. Options > Select export options
ZBrush
Use Decimation Master to appropriately reduce the polygon count. Zplugin > 3D Print Hub > Export as STL.

You can learn more about the different types of CAD software for 3D printing in this article of the Knowledge Base.

Rules of thumb

  • Export with a 0.001 mm chord height and 15o angular tolerance for best 3D printing results.
  • Avoid exporting unnecessarily large STL files.
  • Upload your STL files and we will auto-fix small geometry imperfections.

More resources for engineers

Guide to plastics cover image

What materials have the best repeatability?

Read article
article-1million-image-1.png

Guide to designing for product scalability

Read article

What is GD&T? How to reduce manufacturing errors and improve quality

Read article

How do you design parts for MJF (Multi Jet Fusion) 3D printing?

Read article

What is design for manufacturability (DFM)?

Read article
3D Printing STL files: A step-by-step guide

3D printing STL files: A step-by-step guide

Read article
SLA 3D Printing materials compared

What’s the right resin for SLA? 3D printing materials compared

Read article
How to design parts for Binder Jetting 3D printing

How to design parts for binder jetting 3D printing

Read article
Aerospace 3D printing Applications

3D printing for aerospace and aviation

Read article
Understand and fix common STL file errors

What are the top STL file errors? Here's how to fix them

Read article
3D Modeling CAD Software

What is CAD modeling? Comparing design software for 3D printing

Read article
How to design parts for Material Jetting 3D Printing

How to design parts for material jetting 3D printing

Read article
Guide to plastics cover image

What materials have the best repeatability?

Seeking consistency and predictability in your parts? Check out our guide on repeatability, which highlights the materials that will perform the same way time and time again.

Read article
article-1million-image-1.png

Guide to designing for product scalability

How can you create a part or product that’s ready to move from prototype to production? Check out our article, which offers tips and tricks for designing with scalability in mind.

Read article

What is GD&T? How to reduce manufacturing errors and improve quality

What is Geometric Dimensioning and Tolerancing (GD&T) and how is it used? This article explores the basics of how and when to use GD&T to get the best results out of custom part manufacturing.

Read article

How do you design parts for MJF (Multi Jet Fusion) 3D printing?

Multi Jet Fusion (MJF) 3D printing can create highly accurate, complex industrial parts more efficiently - and potentially more cost-effectively - than other industrial 3D printing processes. This article covers how to design parts for MJF, common applications of the technology and key best practices.

Read article

What is design for manufacturability (DFM)?

Design for manufacturing (DFM) means taking a design-first approach to manufacturing. In this article, we look at the overall DFM process, the necessary steps for a successful outcome, examples of DFM done right and how to get the most out of your own processes.

Read article
3D Printing STL files: A step-by-step guide

3D printing STL files: A step-by-step guide

Learn how to avoid low quality 3D prints or unnecessarily large files by exporting your STL file in the correct resolution.

Read article
SLA 3D Printing materials compared

What’s the right resin for SLA? 3D printing materials compared

What are the different materials available for SLA 3D printing? This article compares the main printing resins, including standard, tough, durable, heat resistant, rubber-like, dental and castable, by material properties. Find the best material option for your application.

Read article
How to design parts for Binder Jetting 3D printing

How to design parts for binder jetting 3D printing

A comprehensive guide on designing parts for Binder Jetting, covering the printing process, design specifications and material options.

Read article
Aerospace 3D printing Applications

3D printing for aerospace and aviation

How does 3D printing accelerate innovation in the aerospace and aviation industry? In this article, we explain how 3D printing and additive manufacturing are commonly used in aerospace and how they improve prototyping and end-use part production for these industries.

Read article
Understand and fix common STL file errors

What are the top STL file errors? Here's how to fix them

What are the most common STL file errors and how will they affect your ability to export models for 3D printing? Learn to identify the errors you may encounter when working with STL files and how to fix them so they don't delay your next 3D printing run.

Read article
3D Modeling CAD Software

What is CAD modeling? Comparing design software for 3D printing

What is CAD modeling and why is it an essential tool for digital manufacturing? Explore the types of CAD software available for bringing ideas into the physical world via digital 3D modeling. Find the right software tools for your application.

Read article
How to design parts for Material Jetting 3D Printing

How to design parts for material jetting 3D printing

This article explains how to design Material Jetting 3D printed parts including technical design specifications, materials, limitations and an introduction into the post-processing options available.

Read article

Show more

Show less

Ready to transform your CAD file into a custom part? Upload your designs for a free, instant quote.

Get an instant quote