Flexible resins are an exciting group of materials with low shore hardness and quite a lot of means of use. However, they usually come with several downsides. In general, they are more difficult to print (compared to rigid resins), they are often made from dangerous chemicals and some of them require washing in toxic solvents (Loctite IND475 + Cleaner T, for example). This led us to make our own flexible resin with good printability, easy washing in safe chemicals, and low toxicity. The Flex 80 is a virtually odorless, non-toxic resin suitable for hobby and professional use. It comes with fast print speed, great detail, the possibility to print large objects, and easy washing with IPA.

Basic properties of SLA resins and comparison to flexible filaments

First, let’s start with a general overview and comparison with other flexible materials as some of you may have more experience with FFF 3D printing than MSLA. But if you’re already familiar with flexible MSLA resins and want to know more about Prusament Resin Flex80 in particular, feel free to skip this chapter.

Shore hardness

For filaments, there are various shore hardnesses but most of them are quite high. They usually don’t go much lower than values around 90A and 40D. One of the main reasons is the hard manufacturing of a soft filament, the other is print difficulty. Simply said, the softer the filament is, the higher the chance of various print failures. But luckily, this doesn’t apply to the SLA materials. Flexible resins in general can go much lower with shore hardness since the SLA (MSLA in our case) technology works completely differently. This means that you can make quite soft and smooth models, even with thick bodies.

Also, there is a great difference in the hardness of cured and uncured models. While the flexible filament has an exact number that remains unchanged, flexible resin hardness may vary according to the post-curing process. For example, uncured Prusament Resin Flex80 comes with hardness 75A, while cured (after 60 min) reaches maximum values around 85A.

Rebound properties

There is a small catch in rebound properties. While flexible filaments tend to rebound almost instantly, flexible resins remain bent for a longer time and may only return to their normal position after several seconds (this varies between different resins).

Rebound properties of flexible filament (left) and flexible resin (right)

Other mechanical properties

The other mechanical properties are somewhat different from filaments too. The flexible filament is virtually unbreakable. The flexible resin, on the other hand, is much less resilient and may crack if bent too much. Also, if you use it for making a custom gasket and squeeze it with high pressure between two parts, it may not resist and crack too.

Flex80 properties

Now, let’s focus on the Prusament Resin Flex80 only. In general, it is a versatile material developed for easy printability, and overall high performance while maintaining low price. The greatest benefit is its low toxicity with no need for difficult postprocessing or washing in expensive and dangerous chemicals. It fulfills the following requirements:

  • flexible and energy-damping properties
  • low viscosity
  • washable in IPA with no need for other chemicals
  • low odor and high safety according to the skin irritation test standards
  • short exposure times
  • high resolution allowing printing of all kinds of models with fine structures
  • high print reliability even when printing larger and supported objects
  • easy support removal
  • easy postprocessing with Original Prusa CW1S
  • overall high performance with a low price

The material’s mechanical properties simulate rubber-like materials such as car tires, shoe soles, or ebonite hard rubber. Elongation at break reaches 60 % after 60 min of curing in CW1S. Prolonged curing times are needed to reach the final properties of the material during which stiffness, hardness, and ductility increase. Increased temperature helps to perform the curing process to the full extent. The material offers good energy absorbing and damping capabilities with slow relaxation and slow return to its original shape.

Energy damping properties of Flex80

Basic material’s properties after 60 min curing in CW1S:

  • Tensile modulus 17 MPa
  • Tensile strength 9 MPa
  • Tensile elongation 60 %
  • Shore hardness 70-80A

Tensile properties were measured for 1 mm thick tensile specimens with a 50 mm/min deformation rate.

Flex80 resin family is processable by all types of SLA 3D printers using exposure in the 370-410 nm range. However, the resin was developed in particular for printers using the 405 nm wavelength, such as the Original Prusa SL1S SPEED. The combination of Prusa material and hardware guarantees the best results. Rigorous internal testing of our materials and technologies offers ready-to-use printing profiles for carefree and user-friendly printing.

For certain extremely complex and large objects, adjusting the settings may be required. We suggest setting a higher concentration of supports (for example 200 %) with higher penetration depth (for example 0.6 mm). A high viscosity profile with slow tilt and Z-hop is also highly recommended.

Flex80 low toxicity

No hazardous chemicals, such as TPO, ACMO, and BPA, are used for Flex80 resin formulation (check out our previous article on this topic). Also, the Flex80 is virtually odorless. The resin complies with skin irritation standards making it suitable even for various haptic models, rubber parts of various tools, and similar. It may be also used for various educational purposes, where skin contact safety is necessary. Our resins were tested for skin irritation standards at the Czech National Institute of Public Health.

Applications of Flex80:


Models and Figures

High resolution, print speed, and user-friendly processing make this resin a great choice for printing highly detailed visual models. Improved durability may come in handy when roughly treated. With an impact energy of over 100 kJ/m2, it offers great endurance for models.                                                                                                                                

Clear translucent models

FLEX80 Transparent Clear resin is specially developed to minimize discoloration (i.e. yellowing) of the prints after curing. Its optical clarity offers a great choice for clear prints in various applications ranging from figures, microfluidic reactors, fashion, art, or design. Its mixtures with other types of Prusament flex resins can increase their translucency.

Flexible microfluidic cells, pumps, and devices

Flex80 may be used for research purposes in the field of microfluidics. With transparent clear resin and high print detail, it is possible to mix various fluids in molecular biology, microelectronics, and other high-tech fields.

With mechanical properties similar to rubber, the Flex80 resin is a great choice for prototyping tires whether you are a hobbyist, RC car enthusiast, or professional in the industrial segment.

Material’s mechanical properties and print performance even for large and tall models allow the printing of realistic models of organs and soft tissues. This makes it a great tool for education and surgical practice purposes. Models can be sterilized by hydrogen peroxide or heat and water steam to perform in a medical laboratory.


The combination of flexibility and safe skin contact makes the Flex80 suitable for printing various durable grips, spare rugged parts, and similar.

Watertight seals

At shallow depths, the Flex80 can be used for flexible parts of various watertight housings. This may be useful for crafting a watertight flashlight for snorkeling, for example. Learn more in our older article about watertightness.
Rugged housing

Flexible and energy-damping properties offer great protection for electronic devices.

Excellent printing properties, simple postprocessing, and low price make the Prusament Resin Flex80 suitable for both hobbyists and professionals. Plus, without dangerous chemicals and odor, it is safe for various education purposes and use at home. Have you already tried printing with our Flex80? If you like it, don’t forget to leave a comment or share your makes!

Happy printing!