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Photopolymers for 3d printing


What Is Photopolymerization in 3D Printing? | Blog Posts

During operation, 3D printers often release heated material in a liquid or semi-solid state. Doing so allows the 3D printer to release an even and consistent amount of material, thereby reducing the risk of defects like ghosting. Finished objects, however, must be solid, which is where photopolymerization comes into play. Photopolymerization is used to harden the deposited material so that the finished object achieves a solid state.

The Basics of Photopolymerization

Photopolymerization is the curing process that’s characterized by the use of ultraviolet (UV) light. In 3D printing, it’s used to cure the deposited material. When exposed to UV light, the deposited material cures. Curing results in physical changes to the deposited material, turning it from a liquid or semi-solid state to a solid state.

Not all materials support photopolymerization. Rather, this curing process is used exclusively for photopolymer materials. A photopolymer material is a type of resin material that hardens under UV light. Other types of materials are generally unaffected by UV light. For photopolymerization to work, a photopolymer material must be used in the 3D printer.

How Does Photopolymerization Work?

Photopolymerization works by leveraging the UV-sensitive properties of photopolymer materials. For most 3D printing processes, layers of deposited material are cured via a UV light. After the 3D printer has completed a layer, a UV light is projected over it. The UV light triggers a reaction within the deposited material, essentially solidifying it. The cured material changes to a solid state, allowing for the production of a solid and finished object by the 3D printer.

Some of the most common 3D printing processes that support photopolymerization include the following:

  • Digital light processing
  • Continuous liquid interface production
  • Stereolithography

Benefits of Photopolymerization

Of course, there are other curing methods available for 3D printing materials. Some 3D printing processes use a laser, for instance. The laser moves across the top of the print bed while curing the underlying material. When compared to lasers, as well as other curing methods, photopolymerization offers several advantages.

Photopolymerization is highly effective at solidifying deposited materials. It’s able to change the physical properties of the deposited material so that it’s stronger and better protected against damage.

With photopolymerization, entire layers of deposited material can be cured at once. This is in stark contrast to laser-curing methods, which generally only cure a small section of material at once. Because it’s capable of curing entire layers at once, photopolymerization can be performed very quickly.

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3D Printing Photopolymer Parts | PolyJet, SLA | Stratasys Direct

Photopolymers utilized in 3D printing offer fine feature detail along with a final-product aesthetic realism unmatched by other technologies. With prototypes and concept models, simulating cosmetics and feel of the end-product is often essential. That’s where photopolymers really shine. With little finishing needed, photopolymer technologies (such as PolyJet or Stereolithography) make aesthetic parts rapidly, getting your idea into your hands and in front of your team that much quicker.

Photopolymers are thermoset materials, or polymers, that change properties when exposed to ultraviolet light. These materials can be clear or opaque, flexible and rigid, and can be specially formulated to accommodate unique application needs.

Suitable for models and prototypes that don’t require a long shelf-life, photopolymers have limited durability. They are not UV stable and can become discolored or deformed over time. These properties are essential considerations when working with photopolymers, but when testing a particular look or functionality of a prospective design, the material remains unmatched in fine detail and smooth finish. At Stratasys Direct, we offer a wide range of photopolymers for two technologies: PolyJet and Stereolithography.

PolyJet

PolyJet photopolymers have properties that range from rubber to rigid, transparent to opaque, neutral to full color. PolyJet technology also allows us to combine several materials in one model to fulfill specific requirements. We’re able to simulate over-molding with two different photopolymers to give prototypes exact product feel. Additionally, PolyJet prints in full color, adding another level of customization and possibilities for final product aesthetics.

PolyJet builds by jetting layers of liquid photopolymer as thin as 16 microns (0.0006”) layer by layer as a UV light cures simultaneously. PolyJet can print rigid and flexible materials in a single build to create over-molded parts without tooling. The technology delivers parts with shore hardness ranging from 27A-95A. Because PolyJet doesn’t require hard tooling to deliver an over-molded part, it is frequently used for prototypes requiring an elastomeric surface, such as grips or buttons, or for testing material hardness.

By blending two or three base resins to create nearly 1,000 composite materials with specific, predicable properties, PolyJet photopolymers expand your possibilities, because a range of hues, translucencies, Shore A values and other properties can be achieved for imaginative prototypes.

Stereolithography

Stereolithography (SL) photopolymers are epoxy or acrylate based resins that can create clear or opaque, strong and rigid parts. These materials mimic the properties of ABS, polycarbonate and polypropylene in layers as thin as 0.002”. At Stratasys Direct, we offer specially formulated SL photopolymers for applications like investment casting patterns.

Stereolithography builds parts with a precise UV laser to cure and solidify thin layers of resin. Post-build, SL parts require some support material removal and further UV curing, and other requested post-processing. Our finishing expertise can take your SL prototypes and transform them into a replica of your finished product. Custom finishing, texture, color, artwork, EMI/RFI shielding, plating and other functional coatings can bring additional value to prototyping and models.

Stereolithography materials differ from PolyJet in that some offer higher impact resistance, heat deflection temperature and humidity resistance for functional prototyping or patterns. At Stratasys Direct, we offer a unique near-hollow build style with Stereolithography that allows us to build large concept models at the fraction of the weight. Use SL photopolymers to build light, large-scale parts in much faster and at less cost with this method.

Photo-Quality Finish with Photopolymers

The ultimate benefit of building parts with PolyJet and SL photopolymers is the ability to get your vision into your hands much faster than conventional manufacturing methods. PolyJet and SL offer highly-cosmetic, sometimes large and extremely lightweight models delivered right on time.

Choosing a liquid photopolymer for a 3D printer.

Classification of materials for SLA/DLP 3D printing.

Contents:

  1. Introduction
  2. SLA Overview
  3. SLA Standard Resins
    1. Standard photopolymer resin - Standard
    2. Clear Photopolymer Resin - Clear
  4. Engineering photopolymer resins
    1. Rigid photopolymer resin - Tough (like ABS)
    2. Durable photopolymer resin - Durable (PP-like)
    3. Heat resistant photopolymer resin - Heat resistant
    4. Rubber-like photopolymer resin - Rubber-like (Elastic)
    5. Ceramic photopolymer resin - Ceramic filled (Hard)
  5. How to choose the right resin for your application
  6. Dental and medical SLA resins
    1. Medical Device Photopolymer Resin - Custom Medical Appliances (Class I Biocompatibility)
    2. Dental Long Term Biocompatible Resin (Class IIa Biocompatible)
    3. Biocompatibility class I vs biocompatibility class IIa
  7. Cast SLA resins
    1. Cast resin for jewelry making
  8. Generalized rules

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This article compares photopolymer resins using Formlabs SLA 3D printing products –

Catalog of photopolymer 3D printers

Photopolymers from FormLabs

Detailed review of the Formlabs Form 3 3D printer

Introduction

The stereolithography prints plastic parts with high resolution, good fine detail and smooth surface. Due to the variety of photopolymer resins available for SLA, this technology is used in many different industries:

  • "Standard" photopolymers are used for prototyping

  • Engineering photopolymers have certain mechanical and thermal properties

  • Dental and medical photopolymers have biocompatibility certificates.

  • Cast photopolymers have a zero ash content after burning.

SLA 3D Printing Resin Overview

SLA uses a laser to cure a liquid photopolymer resin. This process is called photopolymerization. Various combinations of polymers and other additives that are part of the resin allow you to get different material properties.

The main advantages and limitations that are common to all resins in SLA 3D printing are:

Benefits:

Weaknesses:

Base Resins for SLA

Post-Processing SLA/DLP 3D Printing Article


Standard photopolymer resin - Standard

Standard resins produce parts with high stiffness, detail and a smooth surface. The low cost of resins, from $250 per liter, makes them ideal for prototypes.

The color of the resin also affects its properties. For example, in FormLabs products, gray resin is suitable for models with fine details, and white resin for parts that require the smoothest possible surface.

Benefits of using Standard grade resins:

Cons Standard:

Also included in the class of "Standard" photopolymer resins from FormLabs is the Color KIT - a set of special dyes and "Color Base" photopolymer resin for mixing and obtaining a variety of color solutions. This eliminates the need for painting parts after 3D printing.

FormLabs Engineering Photopolymer Resins

Engineering resins have a range of properties for injection molded plastics.

All engineering resins require additional UV curing, such as using the Form Cure, to achieve their maximum properties.

Tough photopolymer resin - Tough (ABS equivalent)

Tough resin was developed for models that need to withstand high loads and be durable.

This material produces strong, shatter-resistant parts and functional prototypes such as snap-on housings.

Pros:

Cons:

Ideal for: functional prototypes, mechanical parts


Durable photopolymer resin - Durable

Durable resin is a wear-resistant and flexible material with mechanical properties similar to polypropylene.

Durable photopolymer produces models with a smooth glossy surface and high resistance to deformation.

Durable Resin is ideal for:

  • Bushings and bearings;
  • Various functional compounds

Pros:

Cons:

  • Not suitable for thin wall parts (recommended minimum wall thickness 1mm)

  • Low heat distortion temperature

  • Low flexural strength (lower than hard resin)

Ideal for: functional prototypes.


Refractory Photopolymer Resin - Formlabs High Temp Resin

The heat resistant resin is ideal for parts that require high temperature resistance and operate at high temperatures.

Formlabs High Temp Resin provides the highest melting point (HDT): 238°C at 0.45 MPa.

The resin should be used to print detailed, accurate prototypes with high heat resistance.

Pros:

Cons:

Flexible Resin

Rubber-like resin allows flexible parts to be made. This material has a low tensile strength and high elongation at break and is well suited for parts that will be bent or compressed.

It can also be used to add ergonomic features to multi-material assemblies such as: dies, wearable prototypes, handles, pads and grips.

Pros:

  • High flexibility (high elongation at break)

  • Low hardness (simulates 80A durometer rubber)

  • High impact resistance

Cons:

  • Doesn't have all the properties of real rubber

  • Requires extensive support structures

  • Material properties deteriorate over time as the part is exposed to ultraviolet radiation (sunlight)

  • Not suitable for thin wall parts (recommended minimum wall thickness 1mm)

Ideal for flexible prototyping.

Ceramic photopolymer resin - Rigid Resin

This resin is reinforced with glass, which provides very high rigidity and a polished surface. The polymer is very resistant to deformation and is excellent for 3D printing thin elements.

Ideal for: molds and tooling, jigs, manifolds, retainers, electrical and automotive fixture housings

Thermal management components printed with SLA ceramic (hard) resin. Image credit: Formlabs

How to choose the right resin for your application

The table below shows the main mechanical properties of photopolymers for SLA:

Source: Formlabs

Standard resin ( standart ) 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 a good part surface makes it ideal for visual prototypes and art models.

Durable ( durable ) resin has the highest impact strength and elongation at break of any other SLA material. Best suited for prototyping parts with moving parts and latches. It lacks, however, the strength of thermoplastic 3D printing materials such as SLA nylon.

tough tough resin is a compromise between the material properties of tough and standard resin. It has a high tensile strength, so it is best suited for rigid parts that require high hardness.

heat resistant resin ( heat resistant ) can withstand temperatures above 200 o C, but has poor impact strength and is even more brittle than standard resin.

ceramic ( ceramic reinforce ) resin has the highest tensile strength and flexural modulus, but is brittle (poor elongation at break and toughness). This resin is preferred for thin wall parts that require increased rigidity.

The graphs below compare the mechanical properties of the most common SLA materials visually:

Comparison chart for elongation at break and toughness for common SLA printing specifications and standard media. Image courtesy of Formlabs.

Stress-strain curves for conventional SLA technologies and standard materials. Image credit: Formlabs

Pros:

Cons:

  • Moderate wear and tear resistance

Ideal for: Surgical aids and appliances

Dental Long Term Biocompatible Resin - Dental Long Term (Class 2A biocompatible)
0114

These resins are specially formulated for long term dental fixtures. Class 2A biocompatible resins can come into contact with the human body for up to a year.

High resistance to breakage and wear make this resin ideal for making rigid cotter pins or retainers.

Pros:

Cons:

  • High price

Ideal for: durable dental instruments, fracture and wear resistant medical parts, rigid cotter pins, retainers

What is the difference between class 1 and class 2a biocompatibility?

Class 1 biocompatibility rules apply to materials that are allowed to be used for:

  • non-invasive devices that come into contact with intact skin

  • devices for temporary use or short-term use in the mouth or ear canal or in the nasal cavity

  • reusable surgical instruments

Class 2a biocompatibility rules apply to materials that are allowed to be used for:

  • devices that come into contact with bodily fluids or open wounds

  • devices used to introduce substances into or remove substances from the human body

  • invasive short-term devices such as invasive surgical items

  • long-term implantable devices placed in the teeth

Photopolymer resins in SLA 3D printing for jewelers


Jewelry resins

This material allows you to print models with fine details and a smooth surface without leaving ash or residue after burning.

Cast resin allows you to get the finished product directly from design to precision casting with just one 3D printed part. It is suitable for making jewelry and other small and complex components.

Pros:

Cons:

Ideal for: investment casting, jewelry making

    SLA/DLP 3D printer catalog

    Photopolymers from FormLabs

    Post-Processing SLA/DLP 3D Printing Article

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    Overview of photopolymers for 3D printing

    Rapid prototyping

    Author: Nikita Kudryashov

    Author: Nikita Kudryashov

    Clara A: transparent photopolymer | Formula L1 and Formula W: analogues of ABS | Magna L90, Magna L100 and Magna W120: heat-resistant photopolymers | Robusta G and Robusta LR: tough and durable | Flexa W: analogue of polypropylene | Why ProtoFab? | Order test 3D printing

    Laser stereolithography (SLA) has established itself as one of the most advanced technologies for prototyping, tooling, functional products and burnout master models on a 3D printer. The highest accuracy and strength of models, the ability to create objects with complex geometry, the speed of additive installations, as well as the ideal surface quality - these are the main advantages of the technology using photopolymer resin as a consumable material.

    Photopolymers are versatile plastics that make it possible to obtain high-quality models with desired properties, such as strength, elasticity, transparency, and resistance to high temperatures.

    In this article, we will provide a brief overview of ProtoFab's range of materials. Based on solid experience, years of scientific research and a deep understanding of market needs, ProtoFab has made a real breakthrough in the field of photopolymers for 3D printing using SLA technology. The products of this Chinese company significantly reduce the cost of production and seriously compete with the established monopoly of Western manufacturers.

    Recall that ProtoFab not only develops and manufactures stereolithographic 3D printers and consumables, but also fulfills customer orders in its own rapid prototyping centers. This allows the company to test manufactured materials and equipment, quickly respond to customer requests and improve product quality.

    iQB Technologies experts recommend article: 7 reasons to choose a ProtoFab photopolymer 3D printer

    Clara A: transparent photopolymer

    Most photopolymers for SLA printers are white opaque materials. Due to the high requirements for transparency and colorlessness, as well as the difficulty of solving common problems (for example, the formation of bubbles during molding), transparent photopolymers for stereolithography are a rather rare product in all world markets. This niche is monopolized by several large manufacturers of 3D printing materials. High prices for their products increase the cost of 3D printing and seriously slow down the process of industrialization.

    Prototype to check the appearance of the product. Transparency allows you to see the internal structure

    One of the factors that can accelerate the development of additive technologies will be the development of colorless photopolymers with a high degree of transparency that do not form bubbles. The successful launch of such a product can play an important role in the development of the 3D printing market on the way to Industry 4.0. At the moment, all transparent photopolymers of large manufacturers have certain problems: discoloration (for example, yellowing), excessive hygroscopicity or insufficient transparency.

    Clara A denture model

    During the development of Clara A, the ProtoFab research team performed many experiments and compared hundreds of formulas. The resulting material has excellent transparency, excellent water resistance and dimensional stability, does not yellow and can be used in fast production cycles. No bubbles are formed during the molding process. Printed products are characterized by a smooth surface, dimensional accuracy, strength and impact resistance.

    Due to its ease of processing and the ability to create an “acrylic effect”, Clara A finds application in various fields, for example, in the production of headlights and other automotive components, electronics, lamps, optical research, as well as in the creation of master models or conceptual models and prototypes. This photopolymer can be used for the production of single items - lenses, packaging, models for hydrodynamic and aerodynamic tests, conceptual models.

    Formula L1 and Formula W: Similar to ABS

    3D printed product made of Formula L1 photopolymer

    The high-strength Formula L1 material is a great alternative to ABS in 3D printing. Similarity to ABS is achieved due to the opaque white color, as well as moisture resistance and resistance to yellowing. The second photopolymer in this series is Formula W. The material has excellent strength, heat resistance, and is easy to process. All this allows Formula L1 and W to be used for almost any purpose - from the creation of functional prototypes and concept models to the production of small batches of products.

    Creation of a ski helmet prototype from ProtoFab Formula W material

    Formula L1 Resin Case Study: SLA Concept Car: How It's Made in China

    Magna L90, Magna L100 and Magna W120: Heat Resistant Photopolymers

    Magna L90 and Magna L100 withstand temperatures up to 70°C and 80°C respectively, making them similar to ABS in both appearance and physical characteristics. The ease of fabrication and excellent detail make these photopolymer resins suitable for use in automotive, heat-resistant or lighting fixtures, orthodontics or electronics cases. The surface of the products is smooth and requires almost no post-processing, which significantly reduces the production time for trial models. Magna L100 is also resistant to solvents and oils.

    3D printed product made of Formula L1 photopolymer

    The most advanced material in this series is Magna W120, resistant to temperatures up to 90°C and aggressive substances. It is an ideal choice for temperature and wind tunnel testing.

    Robusta G and Robusta LR: tough and durable

    Robusta G is a white photopolymer with high rigidity, precision and strength, which allows it to be used for the most demanding tasks. It is an excellent replacement for CNC-machined polypropylene or ABS and is excellent for producing functional prototypes, high-detail vacuum casting master models, mounting and fastening fixtures, clip-on or precision-fit parts.

    3D printed product made of Formula L1 photopolymer

    Robusta LR, part of the High-Tough series, features increased elongation at break and impact strength, as well as excellent accuracy and high temperature resistance. Similar to ABS and other thermoplastics, the product's smooth surface texture is easy to clean, making it ideal for functional prototypes and high-strength precision models, fasteners, clip-on or precision-fit parts.

    Flexa W: equivalent to

    polypropylene

    Material Flexa W

    An exceptionally flexible photopolymer that also has excellent strength and moisture resistance.

    Learn more