Guide to Working with 3D Printing Flexible Materials

Flexible materials are essential in 3D printing, enabling applications that require movement, cushioning, or adaptability. They are widely used in areas such as footwear, medical devices, seals, flexible joints, and wearables, where softness and elasticity are critical to performance. As 3D printing flexible materials and 3D printing soft materials continue to grow in demand, selecting and processing them correctly becomes increasingly important.

However, working with flexible materials also introduces challenges – printability, post-processing, and durability often complicate production and application. This guide explores how to understand, select, and print flexible materials effectively, helping users balance elasticity with mechanical strength for their specific use cases.

To work effectively with 3D printing flexible material, 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.
 

What Makes a 3D Printing Material Flexible?

A 3D printing material becomes flexible when it features:

• Low modulus, allowing bending and compression
• High elongation at break, enabling stretch
• Elastomeric polymer backbones, such as urethanes or soft acrylates
• Plasticizers or flexibilizing monomers, which soften the network
• Proper crosslink density, controlling softness vs toughness

In resin-based printing, oligomer and monomer selection directly influences softness and stretchability.

A wide range of material families offer flexible characteristics in 3D printing, each with specific performance profiles tailored to different needs. Below is an overview of the most relevant families and their standout products.

• Polyester Acrylates: Polyester acrylates are known for their softness and stretchability. GENOMER* 3135 is a leading example offering a soft feel, and incorporating bio-renewable content, making it a more sustainable option. It delivers one of the best balances between elongation (up to 250%) and tear strength, making it ideal for applications that demand both flexibility and durability.
   
• Urethane Acrylates and Methacrylates: This family excels in combining toughness with elasticity. GENOMER* 4270 and GENOMER* 4256 offer a balanced elongation and softness, making it suitable for elastomer.
   
• Acrylated Oligoamines: Acrylated oligoamines serve as performance enhancers in formulations. GENOMER* 5695, even at low concentrations, significantly improves printing speed, elasticity, and cure depth in elastic formulations. It’s often used as an additive to boost overall efficiency and performance in flexible resins.
   
• Speciality Resins: Some specialty resins offer unique enhancements for specific needs. GENOMER* 7302, for example, is used at low concentrations to enhance surface curing of elastomeric materials, improving final part quality and surface consistency without compromising flexibility.

These material families and their respective resins provide a strong foundation for tailoring flexibility in 3D printed parts, depending on the specific application and required mechanical profile.

Demonstration from our RadLab

Resin-Based Flexible Materials (DLP / SLA)

• Offer superior detail, higher elongation, and better surface finish
• Suitable for medical, fashion, prototyping, seals, and soft-touch components
• Enable tailored formulations via oligomers and additives (e.g., GENOMER* range)

This comparison helps users understand where different 3D printing flexible materials fit depending on the technology.

PolyJet / Material Jetting

Material Jetting technologies produce rubber-like materials with:

• Exceptional detail
• Multi-material combinations (hard + soft in one print)
• Precise tuning of Shore hardness

Material jetting 3D printing is particularly well-suited for prototyping overmolded components, grips, handles, gaskets, and tactile interfaces

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.

Because of these trade-offs, material selection must be closely aligned with the application’s requirements. Below are examples that illustrate how different formulations are optimized for specific use cases:

High elongation, low tear strength:

• GENOMER* 1122 is suitable for stretchable items where maximum flexibility is desired over tear resistance.
• GENOMER* 4269/M22 offers similar high elongation with lower tear strength, making it ideal for soft, stretchable applications.

Balanced properties:

• GENOMER* 4277 delivers a good balance between tensile strength and elongation, along with low water uptake, making it well-suited for durable, long-term parts exposed to varying environments.
• GENOMER* 4267 provides a balanced profile of flexibility and strength, making it an excellent choice for gaskets or components under moderate mechanical load.

Understanding these performance trade-offs enables users to strategically choose the right material formulation, ensuring that printed parts perform optimally in their intended roles.

Advantages

• High elasticity and softness
• Excellent energy absorption and cushioning
• Ideal for complex organic shapes
• Enables wearable and skin-contact applications
• Customizable mechanical properties through formulations

Disadvantages

• Can be challenging to print (stringing, warping, deformation)
• Lower stiffness may limit structural use
• Some materials show reduced tear resistance at high elongation
• Post-curing must be carefully controlled to avoid brittleness

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.

In industrial and mechanical applications, flexibility must often be paired with durability, chemical resistance, and mechanical strength. For snap fits and flexible joints, materials like GENOMER* 4212 and GENOMER* 1280M serve as effective flexibilizers, offering good rebound, low viscosity, and minimal yellowing – important for visual and functional longevity. In addition, custom seals and vibration dampers can be formulated using these resins for optimized performance in demanding environments.

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.