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Stereolithography (SLA) can produce plastic parts with high resolution and exactness, fine details, and an easy surface finish. Thanks to the number of resins available for SLA THREE DIMENSIONAL printing, this process has found a large number of applications in diverse industrial sectors::
Standard resins are used for general prototyping
Engineering resins have specific mechanical & thermal properties
Dental & medical resins have biocompatibility certifications
Castable resins have zero ash-content after burnout
On this page the most common SLA material choices are presented. The key benefits of each SLA material will be summarizes and actionable ideas to help you choose the one that is most ideal for your application are presented.
SLA uses an UV laser to cure liquid resin in hardened plastic in a method called photopolymerization. Different permutations of the monomers, oligomers, photoinitiators, and various other additives that comprise a resin cause different material properties.
SLA produces parts from thermoset polymers. Here are the main rewards and limitations that are popular among all SLA materials:
Pros:
Smooth, injection mold-like, surface finish
Fine features & high detail
High stiffness
Cons:
Relatively brittle (low elongation at break)
Not suitable for outdoors use: the material properties may change over time, due overexposure to UV radiation (sunlight)
Susceptible to creep
In the following sections, we will go deeper into material properties that are specific to each SLA resin.
Regular resins produce high firmness, high resolution prints with a simple injection molding-like finish. The low-cost makes them ideal for prototyping applications.
The color of the plant affects its properties. For instance , grey resin is better fitted to parts with fine facts and white resin meant for parts that require a very simple surface.
Pros:
Fine features & high detail
Smooth surface finish
Most economic SLA material
Cons:
Brittle (low elongation at break)
Low impact strength
Low heat deflection temperature
Ideal for: concept modeling, rapid prototyping, art models
Hearing aids 3D printed with SLA in Standard resin
Sharp resin has similar mechanised properties to standard botanical, but can be post-processed to near optical transparency.
Pros:
Fine features & high detail
Smooth surface finish
Transparent
Cons:
Brittle (low elongation at break)
Low impact strength
The optical clarity may change over time, as the part is exposed to UV radiation (sunlight)
Ideal for: showcasing internal features, LEDs housing, fluidic devices
An electric enclosure 3D printed with SLA in Clear botanical during different post-processing methods
Design resins simulate a range of injection-molded plastics to provide technicians with a wide choice of materials properties for prototyping, screening, and manufacturing.
All executive resins require post-curing below UV light to reach their particular maximum mechanical properties
Rough resin was developed for applications requiring materials that can endure high stress and stress. Parts printed in difficult resin have tensile strength (55. 7 MPa) and modulus of elasticity (2. several GPa) comparable to ABS.
This fabric will produce sturdy, shatter-resistant parts and functional representative models, such as enclosure with snap-fit joints, or rugged representative models.
Pros:
High stiffness
Excellent resistance to cyclic loads
Cons:
Not suitable for parts with thin walls (recommended minimum wall thickness of 1 mm)
Low heat deflection temperature
Relatively brittle (low elongation at break)
Ideal for: functional prototypes, mechanical assemblies
A quadcopter prototype 3D printed with SLA in Tough (ABS-like) resin. Image courtesy: Formlabs
Tough resin is a wear-resistant and versatile material with mechanical homes similar to Polypropylene (PP).
Resilient resin can be used for parts that require high flexibility (high elongation at break), low friction and a smooth area finish. Durable resin is specially fitting for prototyping client products, snap fits, the ball joints and low-friction moving parts.
Pros:
High wear resistance
Flexible (relatively high elongation at break)
High impact resistance (higher than Tough resin)
Cons:
Not suitable for parts with thin walls (recommended minimum wall thickness of 1 mm)
Low heat deflection temperature
Low tensile strength (lower than Tough resin)
Ideal for: functional prototypes, consumer products, low-friction and low-wear mechanical parts.
A toolcase with a hinge 3D printed with SLA in Durable (PP-like) resin. Image courtesy: Formlabs
Heat-proof resin are ideal for applications that need high thermal stability and operate at high temperatures.
These types of resins have a warmth deflection temperature between 200-300°C and are ideal for manufacturing heat proof fixtures, mold prototypes, heat and fluid flow gear, and casting and thermoforming tooling.
Pros:
High heat deflection temperature
Smooth surface finish
Cons:
Brittle (low elongation at break)
Not suitable for parts with thin walls (recommended minimum wall thickness of 1 mm)
Ideal for: mold prototyping, casting and thermoforming tooling.
A low-run injection mold 3D printed with SLA in Heat resistant resin. Image courtesy: Formlabs
Rubber-like resin allows engineers to simulate rubber parts which can be soft to the touch. This material includes a low tensile modulus and high elongation at rest, and it is well-suited for items that will be bent or pressurized.
It can also be used to add ergonomic desk features to multi-material devices, like packagings, stamps, wearable prototyping, handles, overmolds and grips.
Pros:
High flexibility (high elongation at break)
Low hardness (simulates an 80A durometer rubber)
High impact resistance
Cons:
Lacks the properties of true rubber
Requires extensive support structures
The material properties degrade over time, as the part is exposed to UV radiation (sunlight)
Not suitable for parts with thin walls (recommended minimum wall thickness of 1 mm)
Ideal for: wearables prototyping, multi-material assemblies, handles, grips, overmolds
A model car tire 3D printed with SLA in Rubber-like (flexible) resin. Image courtesy: Formlabs
Rigid resins are reinforced with glass or additional ceramic particles and result in very stiff and rigid parts, with very smooth surface finish.
Rigid resins offer good thermal stability and heat resistance (Heat Deflection Temperature HDT @ 0.45MPa of 88°C). They have a high modulus of elasticity and lower creep (higher resistance to deformation over time) compared to other SLA resins, but are more brittle than the Tough and Durable resins.
Rigid resin is also suitable for parts with thin walls and small features (the recommended minimum wall thickness is 100 µm).
Pros:
High stiffness
Suitable for parts with fine features
Moderate heat resistance
Cons:
Brittle (low elongation at break)
Low impact strength
Ideal for: molds and tooling, jigs, manifolds, fixtures, housings for electrical and automotive applications
Thermal management components 3D printed with SLA in Ceramic filled (rigid) resin. Image courtesy: Formlabs
The table below summarizes the basic mechanical properties of the common SLA materials:
Standard & Clear | Tough | Durable | Heat resistant | Ceramic reinforced | |
IZOD impact strength (J/m) | 25 | 38 | 109 | 14 | N/A |
Elongation at break (%) | 6.2 | 24 | 49 | 2.0 | 5.6 |
Tensile strength (MPa) | 65.0 | 55.7 | 31.8 | 51.1 | 75.2 |
Tensile Modulus (GPa) | 2.80 | 2.80 | 1.26 | 3.60 | 4.10 |
Flexural Modulus (GPa) | 2.2 | 1.6 | 0.82 | 3.3 | 3.7 |
HDT @ 0.45 MPa (oC) | 73 | 48 | 43 | 289 | 88 |
Source: Formlabs
Standard resin has high tensile strength but is very brittle (very low elongation at break), so it is not suitable for functional parts. The ability to create fine features makes it ideal though for visual prototypes and art models.
Durable resin has the highest impact strength and elongation at break compared to the other SLA materials. It is best for prototyping parts with moving elements and snap-fits. It lacks though the strength thermoplastic 3D printing materials such, as SLA nylon.
Tough resin is a compromise between the material properties of durable and standard resin. It has tensile strength, so it is best suited for rigid parts that require high stiffness.
Heat resistant resin can withstand temperatures above 200oC, but has poor impact strength and is even more brittle than the standard resin.
Ceramic reinforce resin has the highest tensile strength and flexural modulus, but is brittle (poor elongation at break and impact strength). It should be prefered over other engineering resins for parts with fine features that require a high stiffness.
The following graphs representative mechanical properties of the most common SLA materials are visually compared:
Comparative chart for elongation at break and impact strength for common SLA engineering and standard materials.
Image courtesy Formlabs
Stress-strain curves for common SLA engineering and standard materials.
Image courtesy Formlabs
Comparative chart of the material properties of the different engineering resins.
Image courtesy Formlabs
Class We biocompatible resins can be used to make custom medical equipment, such as surgical guides. Parts printed in this resin can be steam sterilized using an autoclave, for a direct use in the operating room.
Pros:
High precision
Smooth finish
Class I biocompatible (short term use)
Cons:
Moderate wear and fracture resistance
Ideal for: surgical aids and appliances
Surgical dental guides 3D printed with SLA in Custom Medical Appliances Resin. Image courtesy of Formlabs
This resins are engineered for long term orthodontic appliances specially. Class IIa biocompatible resins can be in contact with the human body for up to a year.
Their high resistance to wear and fracture make it perfect to produce custom hard splints or retainers.
Pros:
High accuracy
High resistance to fracture and wear
Class II biocompatibility
Cons:
High cost
Ideal for: long term dental appliances, fracture and wear resistant medical parts, hard splints, retainers
Custom dental retainer 3D printed with SLA in Dental Long Term Biocompatible Resin. Image courtesy of Formlabs
Class I biocompatibillity rules refer to materials that are allowed to be used for:
· non-invasive devices that that come in contact with intact skin
· appliances for transient use or short-term use in the oral or ear canal or in nasal cavities
· reusable surgical instruments
Class IIa biocompatibility regulations refer to materials that are allowed to be used for:
· devices that come in contact with body fluids or open wounds
· devices used to administer or remove substances to and from our body
· invasive short-term gadgets, such as for example invasive surgical elements
· long-term implantable devices put into teeth
This material enables printed parts with sharp points and a smooth finish, and can burn up without leaving ashes or residue cleanly.
Castable resin allows the production of parts directly from an electronic design to investment casting through an individual 3D printed part. They are ideal for jewellery and other elaborate and small components.
Pros:
Low ash content after burnout (less than 0.02 %)
Fine features and high detail
Cons:
Low impact and wear resistance
Requires post-processing to ensure best results
Ideal for: investment casting, jewelry making
A ring master prototype before casting 3D printed with SLA in Castable resin
Choose Regular resin for prototypes with an easy injection molding-like surface finish.
For functional prototypes, choose Tough resin if stiffness is usually your main design requirement, Durable resin for parts that need higher impact resistance or have moving parts, and Ceramic reinforced resin for parts with fine features.
Rubber-like resin can produce parts with low hardness and high flexibility, but lack the performance of true rubber.
Heat resistant resin can withstand temperatures above 200oC, but are brittle.
Class I biocompatible resins are suitable to come in external contact with the human body, while Class II biocompatible resins are suitable for short-term invasive devices.
Castable resins have leave very little residues and ash content after burnout (less than 0.02%).
