Taking Mold Creation to the Next Level
High-quality molds can make the difference between successful and failed thermoforming. This means that when designing and creating molds, you should have the knowledge required for thermoforming best practices. Below, we'll tell you how to use SLS 3D printing technology to create high-quality thermoforming molds!
What is Thermoforming?
Thermoforming is a popular manufacturing process that involves heating a plastic sheet and molding it around a tool to create a specific shape. A crucial part of thermoforming is creating the mold that will be used to shape the plastic sheet.
Before We Begin, 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-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 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
Through the video and simple introduction above, I believe you have a basic understanding. So, what are the advantages of using SLS 3D printing? Below are some advantages of SLS 3D printing that are more relevant to thermoforming mold creation:
Internal Porosity, Providing Higher Quality
One of the main advantages of using SLS 3D printing technology for thermoforming is that the produced parts are porous. What's the benefit of this? Porosity means that there's no need to add vent holes to the mold, or the number of required vent holes is greatly reduced. This is crucial for thermoforming molds because vent holes can cause the plastic sheet to bubble and deform during the forming process. Therefore, reducing the creation of vent holes leads to higher-quality prints, increases the stability of the finished product, and saves more time!
Highly Advantageous Material Properties
SLS 3D printing often uses nylon, a material with excellent mechanical properties and temperature resistance. This makes it an ideal material for creating thermoforming molds.
Excellent at Producing ComplexParts
SLS 3D printing technology is particularly adept at producing complex parts because the laser can reach every corner during printing, resulting in a high level of detail. Additionally, SLS 3D printing does not require any support materials; the powder itself acts as a support material, eliminating the need for other materials, thus offering greater design flexibility and allowing for the creation of more complex parts.
Now that we've introduced SLS 3D printing and its benefits, let's officially explain 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 a thermoforming mold for SLS 3D printing, it's crucial to consider the orientation of the part on the build platform. This is because the powder's temperature can vary 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 technique for manufacturing complex shapes and parts without vent holes, its disadvantage is that the manufactured parts often have a rough surface. This is where media blasting comes in. It is highly recommended to use media blasting* for thorough powder removal from 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, which can impact 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 in the mold or reducing their number, making it even 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 precision of the laser and the ability to use powder as its own support material, SLS 3D printing can create thermoforming molds with complex geometries.
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