Thermoforming is a popular manufacturing process that involves heating a plastic sheet and forming it around a mold to create a specific shape. One of the key aspects of thermoforming is creating tools that can be used to form the plastic sheet.
In a previous article, we looked at the different technologies used to fabricate thermoforming tools, as well as their main advantages and applications. In this guide, we will explore how SLS 3D printing can be used to create high-quality thermoforming tools.
What is SLS 3D printing?
Selective Laser Sintering (SLS) is a 3D printing technology that uses a high-powered laser to fuse small particles of plastic powder together. Unlike other 3D printing technologies, SLS does not require any support structures, as the powder acts as its own support.
SLS 3D printing advantages for thermoforming
Below are a few of SLS 3D printing’s many advantages. Those listed here are more relevant to the creation of thermoforming tools:
Internal porosity
One of the main advantages of using SLS 3D printing for thermoforming is that the resulting parts are porous. This means that there is no need to add air holes to the tool, or that the required amount may be significantly lower. This is crucial for thermoforming, as air pockets can cause the plastic sheet to bubble and deform during the forming process.
Material properties
One advantage of SLS 3D printing is that it commonly uses nylon, which offers excellent mechanical properties and temperature resistance. This makes it ideal for creating thermoforming tools.
For example, the Formlabs Fuse 1 SLS 3D printer is compatible with Nylon 12, which has a Heat Deflection Temperature of 171ºC (0.45 MPa) and an Ultimate Tensile Strength of 50 MPa.
Part complexity
SLS 3D printing is particularly good at creating complex parts due to the laser's ability to reach every nook and cranny, resulting in a high level of detail. In addition, SLS 3D printing does not require any support material, allowing for greater design flexibility and the creation of even more intricate parts. This is because the powder itself acts as a support, eliminating the need for additional materials.
Designing and manufacturing thermoforming tools
Here are some tips to remember when creating thermoforming tools using SLS 3D printing.
Part orientation
When designing thermoforming tools for SLS 3D printing, it is important to consider the orientation of the part on the build platform. This is because the temperature of the powder can vary depending on the location of the part, which can cause warping.
If the tool you are designing is wide and relatively flat, it is recommended to 3D print it at a slight angle of 20º to minimize warping.
Post-processing and surface finish
Although SLS 3D printing is an excellent technology for creating complex shapes and parts with no air holes, a downside is that the resulting parts often have a grainy surface finish. This is where media blasting comes in. It is highly recommended to achieve a smoother finish.
SLS 3D printed tool: Surface texture
In addition, tools can be polished or coated to achieve a different finish, providing more options for customization. However, it is important to be aware that altering the surface of the tool may affect its porosity, which can impact the final result of the thermoforming process.
SLS 3D printing: Tool cleaning process
Recommended SLS materials for thermoforming
Nylon 12 is the most popular material used for SLS 3D printing, and it is ideal for creating thermoforming tools. This is due to its excellent mechanical properties and temperature resistance. Nylon 12 has a heat deflection temperature of 171ºC (0.45 MPa) and an ultimate tensile strength of 50 MPa. Additionally, the resulting parts are porous, eliminating the need for air holes in the tool or requiring fewer holes.
Applications for SLS thermoforming tools
SLS 3D printing offers several advantages in thermoforming scenarios due to its unique part properties:
- End-use parts. SLS tools provide excellent strength and temperature resistance, while still achieving high dimensional accuracy. As a result, they are well-suited for creating high-quality end-use parts.
- Small batch production. SLS tools typically have a longer lifespan than tools made with other 3D printing technologies, making them a great option for creating tools that will be used multiple times in small batch production.
- Complex geometries. SLS 3D printing allows for the creation of thermoforming tools with complex geometries, thanks to the laser precision and the ability to use powder as its own support material.