Flexible resin is a type of UV-cured 3D printing resin that mimics the properties of rubber. It stands out for it’s ability to create firm but flexible parts. How stiff or flexible these parts are depends on the Shore hardness of the resin when cured. The numbers on the Shore scale indicate how flexible a material is, with the lower numbers denoting more flexibility.
Most 3D printing flexible resins are measured either on the Shore A or Shore D scales. The former ranges from very soft and flexible to hard and semi-rigid, while the latter is reserved for tough and hard materials. Among flexible resins, a Shore hardness of around 80A is pretty common, and it’s similar to the hardness and flexibility of a rubber shoe heel.
When it comes to color, flexible resins tend to be transparent, making them a blank canvas to which you can add dye or pigment to create a color of your choice. Alternatively, you can add some flexible resin in with your usual resins to improve the tensile strength of the latter.
In this article, we’ll introduce you to some of the best flexible resin brands. If you see something you like, just be sure to check that it’s compatible with your machine. Some brands have different variants depending on your type of printer.
Printing Tips
Printing flexible resin does pose some challenges that you won’t encounter with other resins. Implementing a few tricks in the design and printing process will help you get the best quality part.
When printing flexible parts, it’s important that they’re in their final form. For example, if you’re printing a watchband, the model should be designed in the shape of a watchband around someone’s wrist, not flat. The reason for this is that, similar to harder types of rubber, the resin will always try to revert to its original shape; it won’t form as well if you try to bend it into the desired shape after curing.
Print settings largely depend on the brand you’re using, but compared to other resins, you’ll probably want to increase the layer deposit and cure time for flexible resin. When it comes to removing flexible parts from the build platform, insert a scraper under one edge and slowly peel the print off from the build platform’s surface.
3DMaterials
With a shore hardness rating of 80A, 3DMaterials’ SuperFlex is a versatile flexible resin that’s compatible with a wide range of regular or mono LCD 3D printers. The manufacturer promises low shrinkage and exceptional dimensional stability, which is also reflected in several positive reviews.
Some users suggest blending this resin with other cheaper brittle resins to bring the cost down, while still achieving good flexibility and durability. Experienced users report achieving structurally robust prints that boast TPU or rubber-like characteristics. Beginners, however, should be cautious and follow the recommended instructions to avoid potential print breakages.
- Wavelength: 405 nm
- Sizes: 0.5 kg, 1 kg, 5 kg
- Price: ~$60/kg
- Color: Clear
- Shore hardness: 80A
Prusament
Prusa’s flexible resin is made in-house, like their Prusament filaments, and they strive for the same great quality. The resin comes in black, white, and transparent. Their slicer, PrusaSlicer, has built-in resin printing profiles for their Prusa SL1S Speed, so you can complete the whole printing process using only Prusa’s ecosystem.
They also make a tough resin with a Shore hardness of 76D, and it’s perfect for making RC model parts.
- Wavelength: Not specified
- Size: 1 kg
- Price: ~$70/kg
- Colors: Transparent, black, white
- Shore hardness: 82A
Monocure
Monocure Flex100 is ideal for those requiring high-quality and high-performance resin. Monocure recommends using their flexible resin in combination with their Rapid resins. If you’re after a firm, durable print, use a 25:75 ratio (25-g Flex100 to 75-g Rapid resin). For a very flexible result, increase the ratio to 90:10 (90-g Flex100 to 10-g Rapid resin).
This resin can take longer than others to fully cure, with cracks possibly occurring if the resin isn’t properly cured. As a plus, if you want to do a lot of printing and 1-L containers aren’t enough, you can buy a huge 5-L container.
- Wavelength: 225-420 nm
- Sizes: 0.5 L, 1 L, 5 L
- Price: ~$80/L
- Color: Clear
- Shore hardness: Not specified
eSun eResin Elastic
eSun’s eResin Elastic has high flexibility and good tear resistance, making it ideal for projects demanding intricate details as well as intense flexibility. According to eSun, this resin excels in crafting flexible models with complex cross-sections and has a remarkable stretchability of up to 300% of its original size. Further, the low viscosity of this resin helps ensure improved release and molding compared to its previous version, eResin Flex.
The resin is compatible with a wide range of LCD, MSLA, and DLP resin 3D printers. The manufacturer recommends cleaning the printed objects without post-curing them to achieve optimal flexibility and avoid hardening issues.
- Wavelength: 395-405 nm
- Size: 0.5 kg
- Price: ~$100/kg (~$50 for 0.5 kg)
- Color: Transparent Yellow
- Shore hardness: 85-90A
Photocentric
Photocentric’s Flexible UV160TR Resin is compatible with both DLP and LCD resin printers. It boasts a Shore hardness of 86A, making it a great option for functional parts, according to the company.
There was chatter on forums about cleaning prints made with the previous version of this resin, specifically the one tailored to SLA resin printers. One user recommended cleaning Photocentric resin prints with warm water and mild detergent (rather than alcohol).
Officially, though, Photocentric recommends their Resin Cleaner 30, along with very specific wash cycles. They even caution that exceeding their recommendations may negatively impact the prints. All of that is to say, you might want to stick to the manufacturer’s recommendations. Otherwise, your prints might end up a gooey mess.
- Wavelength: 385-405 nm
- Sizes: 0.5 kg, 1 kg
- Price: ~$100/kg
- Color: Clear
- Shore hardness: 86A
Liqcreate
If you’re looking for an even bendier resin, particularly for a functional part, Liqcreate’s Flexible X is a great choice. With a Shore hardness of 55A, the resin produces medium soft prints that are harder than an eraser but softer than car tires. It’s fine to use on most DLP, LCD, and SLA resin 3D printers.
Flexible X represents the middle ground in Liqcreate’s assortment. Thanks to a Shore hardness of 43A, their Elastomer X is softer and more flexible – closer to the eraser side of the spectrum. And if you want harder, Premium Flex with a Shore hardness of 63A is more in the direction of car tires. None of these may sound all that soft, but the Shore hardness does vary a bit with material thickness. The thinner you make the part, the more flexible it tends to be.
- Wavelength: 385-420 nm
- Sizes: 0.25 kg, 1 kg
- Price: ~$155/kg
- Color: Black
- Shore hardness: 55A
Formlabs
Formlabs Flexible 80A simulates TPU or TPE with a Shore hardness of 30D. It’s best suited to functional objects like seals and gaskets or personal products like a watchband. If you need something even more flexible, their Elastic 50A resin produces results comparable with silicon.
As you would expect, these resins are intended to be used with Formlabs machines. This accounts for the higher-than-average price, as they’re high-quality resins.
- Wavelength: Not specified
- Size: 1 L
- Price: ~$200/L
- Color: Transparent
- Shore hardness: 80A
Formlabs IBT
Formlabs Indirect Bonding Tray (IBT) Resin, used widely in dentistry to make flexible indirect bonding trays, is a great biocompatible flexible resin. In fact, it’s the only biocompatible transparent resin on this list. This means that if you need to print something flexible that’s in contact with food or people, such as a mouthguard or a CPAP mask, this is the safest option.
Formlabs IBT resin is more expensive than other resins on this list, but this price point is arguably justified because it’s the only resin here that’s certified non-hazardous for human internal contact. If you’re using a non-Formlabs printer and need IBT resin, you can check out alternatives such as NextDent IBT resin.
- Wavelength: Not specified
- Size: 1 L
- Price: ~$250/L
- Color: Transparent
- Shore hardness: Less than 90A
Tough & Flexible
The resins in this category are measured on the Shore D scale and are harder than those measured on the Shore A scale. These options may be a better choice when you need flexible prints with high toughness and impact resistance. The degree of their flexibility, however, will have a lot to do with the thickness of your model.
Anycubic
Anycubic’s UV Tough Resin is much less flexible than the other resins on this list. Whereas standard resins tend to be brittle, Anycubic’s UV Tough Resin is designed to flex and bend rather than snap when shear force is applied to a printed part. As mentioned, the part’s overall flexibility will depend on its thickness. The hollow ball in the image above demonstrates this resin’s potential.
Alternatively, it can be a great resin for pieces that don’t need to be very flexible but can’t be as brittle as normal resin, such as certain fittings and adapters or finely-detailed miniatures. Likewise, if you’ve printed a part in standard resin over and over again just for it to keep breaking, it might make sense to try printing it in this resin, as the part will be less likely to break when accidentally dropped or stepped on.
- Wavelength: 365-405 nm
- Sizes: 1 kg, 5 kg, 10 kg, 20 kg
- Price: ~$42/kg
- Colors: White, black, grey, transparent, translucent green
- Shore hardness: 76D
Siraya Tech
Siraya Tech’s Tenacious flexible resin is designed for LCD resin printers and is also compatible with DLP printers. For the best results, use a high-quality FEP film-based vat with the resin at 25 °C.
While the regular Tenacious resins (Clear and Obsidian Black) work great for most prints requiring flexibility, the Tenacious Flex Black resin with a Shore hardness of 70A is ideal for projects that demand higher durability and stress tolerance, such as creating gaskets or seals. Costing ~$15 more than the regular Tenacious resin, it comes with better compression properties and faster rebound performance.
Siraya Tech also makes a plethora of other resins for all your printing needs, including resins designed to be easy to print and clean, faster to print, and suitable for higher resolutions. You can mix their flexible resin with any resin of the same wavelength, letting you find the perfect combination of flexibility and stiffness for any project.
- Wavelength: 405 nm
- Sizes: 0.5 kg, 1 kg, 5 kg
- Price: ~$65/kg
- Colors: Clear, obsidian black, flex black, easy gray
- Shore hardness: 65D, 70A (flex black only)
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