Taking Mold Creation to the Next Level
High-quality molds can make or break a thermoforming project. This means you need to have the knowledge of thermoforming best practices when designing and creating your molds. Below, we'll explain how to use SLS 3D printing technology to produce high-quality thermoforming molds!
What is Thermoforming?
Thermoforming is a popular manufacturing process that involves heating a plastic sheet and forming it around a mold to create a specific shape. A key part of thermoforming is the creation of the mold, which is used to shape the plastic sheet.
Before we start, let's understand what SLS 3D printing is!
Selective Laser Sintering (SLS) is a 3D printing technology that belongs to the powder bed fusion family of additive manufacturing processes. It uses a high-power laser to fuse small particles of plastic powder together. Unlike other 3D printing technologies, SLS does not require any support structures, as the powder itself acts as the support. The materials used in SLS powder sintering are granular thermoplastic polymers, which offer a very high degree of design freedom, high precision, and produce parts with good consistent mechanical properties.
The SLS 3D printing process
Based on the video above and the simple introduction, you should now have a basic understanding. So, what are the benefits of using SLS 3D printing? Below are some of the advantages of SLS 3D printing that are more relevant to thermoforming mold creation:
Internal Porosity for Higher Quality
One of the main advantages of using SLS 3D printing for thermoforming is that the produced parts are porous. What is the benefit of this? Porosity means that there is no need to add vent holes to the mold, or the number of vent holes required will be greatly reduced. This is crucial for thermoforming molds, as vent holes can cause the plastic sheet to bubble and deform during the forming process. Therefore, reducing the creation of vent holes can lead to higher quality printed products, increase product stability, and save more time!
Highly Advantageous Material Properties
SLS 3D printing typically uses nylon, a material with excellent mechanical properties and temperature resistance. This makes it an ideal material for creating thermoforming molds.
Excels at Producing ComplexParts
SLS 3D printing technology is particularly good at producing complex parts because the laser can reach every corner during printing, resulting in a high level of detail. In addition, SLS 3D printing does not require any support material, as the powder itself acts as a support, making the design more flexible and allowing for the creation of more complex parts.
Now that we've introduced SLS 3D printing and its benefits, let's officially discuss the process and considerations for using it for creation.
Designing and Manufacturing Thermoforming Molds
Here are some tips to keep in mind when creating thermoforming molds using SLS 3D printing:
Part Orientation
When designing thermoforming molds for SLS 3D printing, it's essential to consider the orientation of the part on the build platform. This is because the powder's temperature changes depending on the part's position, which can lead to warping.
If you are designing a mold that 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
While SLS 3D printing is an excellent technology for manufacturing complex shapes and pore-free parts, its drawback is that the manufactured parts often have rough surfaces. This is where media blasting comes in. It is highly recommended to use media blasting* for thorough powder removal on SLS parts to achieve a smoother surface finish.
*Media blasting is a process for surface cleaning and preparation for various repair, restoration, or coating applications. It involves propelling abrasive material at high speed onto a surface.
Additionally, molds can be polished or coated according to your needs to achieve different surface effects, providing more personalization options. However, it's important to note that altering the mold's surface may affect its porosity, thereby impacting the final outcome of the thermoforming process.
Recommended SLS Materials for Thermoforming
Nylon 12 is the most commonly used SLS 3D printing material and is ideal for creating thermoforming molds. 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, parts made from this material are porous, eliminating the need for vent holes on the mold or reducing the number of holes, making it more convenient!
Applications of SLS Thermoforming Molds
SLS 3D printing offers several advantages in thermoforming applications due to its unique part characteristics:
• End-use parts: SLS molds offer excellent strength and temperature resistance, while also achieving high dimensional accuracy. This makes them ideal for manufacturing high-quality end-use parts.
• Small-batch production: SLS molds typically have a longer lifespan than molds made with other 3D printing technologies, making them the best choice for molds used multiple times in small-batch production.
• Complex geometries: Due to the high precision of the laser and the ability to use powder as its own support material, SLS 3D printing technology can create thermoforming molds with complex geometries.
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