Guide to Dealing with Flexible Materials in 3D Printing

To work effectively with flexible materials in 3D printing, it's important to understand key mechanical properties: elongation, tear strength, modulus, and tensile strength.

• Elongation measures how far a material can stretch before breaking, typically expressed as a percentage of its original length. Higher elongation means greater flexibility.
   
• Tear strength indicates how well a material resists the spread of a tear once it starts – crucial for parts exposed to repeated bending or stress.

• Modulus, or stiffness, defines how much a material resists deformation under force. A lower modulus results in a softer, more pliable material.
   
• Tensile strength is the maximum force a material can endure while being stretched before it breaks, indicating structural robustness.

These properties often trade off against one another. For example, materials with very high elongation typically show lower tear strength, while those with higher tear strength tend to be less stretchy. Finding the right balance between elasticity and durability is essential for achieving reliable, high-performance printed parts that suit their intended function.

Flexible 3D printing materials can be formulated to emphasize either elasticity or toughness, depending on the performance demands of the end-use application. Here’s a comparison between two representative formulations:

• Elastic Formulation: An elastic formulation using 93% GENOMER* 3135, 5% GENOMER* 5695, and a photoinitiator offers good elongation (75%) and reliable printability. This blend prioritizes softness and stretch, making it well-suited for applications such as soft components and flexible seals, where high flexibility, comfort, and surface adaptability are important.

• Tough Formulation: For applications that require more rigidity and strength, a tough formulation based on GENOMER* 4212 combined with ACMO provides lower elongation but very high impact resistance, tensile modulus, and tensile strength. This makes it ideal for parts that need to withstand mechanical stress while maintaining a degree of flexibility, such as PP-like components or rugged wearables.

By adjusting the base resin and additives, users can fine-tune formulations to meet specific performance goals, whether they lean toward softness and stretch or robustness and structural integrity.

Design Guidelines

• Wall Thickness: Use thicker walls (typically ≥1.5 mm) for structural integrity, but maintain flexibility by avoiding overly rigid geometries.

• Support Structures: Opt for minimal, easy-to-remove supports – flexible materials can deform during removal, so reduce contact points where possible.

• Infill Strategies: Use low to moderate infill (e.g., 20–40%) with flexible patterns such as gyroid or honeycomb to maintain elasticity without sacrificing strength.

Print Settings and Curing Methods

• Print Speed: Reduce print speed to improve accuracy and avoid stretching or stringing – typically 15–30 mm/s works best.

• Layer Height: Finer layers (around 50–100 microns) help maintain surface quality, especially for intricate features.
• Curing: Ensure complete post-curing with the correct wavelength and exposure time. Under-curing can result in sticky surfaces and reduced durability; over-curing can cause brittleness. Use recommended UV light sources and rotate parts to expose all sides evenly.

Common Pitfalls and How to Avoid Them

• Stringing: Flexible resins tend to string between travel paths. Minimize this by tuning retraction settings and using lower temperatures if applicable.

• Under-Curing: Parts may feel tacky or lack mechanical strength if not fully cured. Adjust UV exposure and consider using additives that enhance cure depth.
• Warping or Curling: Avoid sharp edges and sudden transitions in geometry that can induce stress. Ensure even bed temperature and consistent ambient conditions during printing.

The landscape of flexible materials in 3D printing continues to evolve, driven by sustainability goals, performance demands, and advances in chemical engineering.

One major trend is the shift toward bio-based oligomers, such as GENOMER* 3135, which combines high elongation, low viscosity and softness with renewable content. These materials address growing environmental concerns without compromising on functional performance, making them increasingly attractive for consumer and industrial applications alike.

Another key direction is the development of custom formulations that achieve hybrid properties – for example, combining flexibility with impact resistance or integrating elastomeric behavior with structural strength.

This enables materials to be tailored more precisely to specific use cases, expanding design possibilities and reducing the need for multi-material assemblies.

Lastly, innovations in photoinitiator chemistry are enabling deeper and more uniform curing, which improves both elasticity and durability. These advances ensure that even complex, thick, or intricate geometries cure thoroughly, resulting in more reliable and consistent mechanical properties across the entire part.

Together, these trends point toward a future where flexible 3D printing materials are more sustainable, customizable, and performance-optimized than ever before.