Stereolithography 3D Printing –The Complete Guide

Stereolithography 3D Printing –The Complete Guide

In this guide, you will find all information you are looking for about Stereolithography.

From the definition, working principle, and advantages to practical applications – you will find everything about Stereolithography right here.

What Is Stereolithography 3D Printing?

Stereolithography is an industrial resin 3D printing technology. This technology is in the vat photopolymerization family.

It uses light for photopolymer curing.

Stereolithography 3D Printing Procedure
Stereolithography 3D Printing Procedure

 

Materials Used In Stereolithography 3D Printing

SLA 3D printing process uses photopolymers. Such polymers guarantee higher precision and stronger prints.  The notable photopolymer resins types to use in SLA 3D printers are as follows;

1. Standard Resins

A standard stereolithography resin is the primary and most affordable of all types. It offers quality surface finish.

For this reason, the standard resin is ideal for decorative parts. Nevertheless, the resin cannot endure high temperatures. It is also more brittle compared to other resin types.

2. Clear Resins

Clear resin is a unique type.

You can fabricate transparent parts like;

  • Camera lenses
  • Windows
  • See-through models
  • Components housing.

However, the main disadvantage of clear resin is extensive post-processing to achieve the desired clear finish.

3. Engineering Resins

Engineering Resins

Engineering resins are thermoplastic that have undergone special blending. The essence is to better their thermal and/or mechanical features than commodity resins.

These SLA 3D printing resins are resistant to corrosives, wear, and high temperatures.

4. Dental Resins

Dental Resins

These are specialized resin based on their intended application. For instance, there are resins for denture bases, surgical guides, and dental prototypes etc.

Dental resins should be biocompatible and exceptionally resistant to continual wear. The SLA 3D printing resins are very costly.

5. Biomaterial Resins

Biomaterial resin formulation come as aqueous solutions. It comprises of biological polymers such as hyaluronic acid, dextran, or gelatin. Furthermore, it can constitute synthetic polymers such as polyethylene glycol.

6. Castable Resins

Castable resins constitute a mix of wax in liquid or powder form. These stereolithography 3D printing materials are essential in creating molds for investment casting.

Components Of Stereolithography 3D Printer

Each standard SLA 3D printer machine comprises of the following 4 key sections:

  • A tank full of the liquid photopolymer: Normally, the liquid resin is a transparent and liquid plastic.
  • A punctured platform submerged in a tank: You immerse the platform into the tank and it can shift up and down depending on the printing process.
  • A high-powered, UV laser
  • A computer interface that regulates both the laser movements and the platform.

Types Of Stereolithography 3D Printer

There are two major variations of SLA 3D printer machine:

1. Top-down SLA 3D Printer

Top-down 3D printer has the laser source overheard the resin tank. Normally, it builds the part facing up.

The build platform starts at the apex of resin vat and goes downwards after each layer. With top-down printers, you can step up to substantially big build sizes without major loss in precision.

 

 Top down SLA 3D Printing Illustration
Top-down SLA 3D Printing Illustration

However, these advanced abilities come at an added cost. The common use of this printer type is in industrial stereolithography 3D printing systems.

2. Bottom-up SLA 3D Printers

The light source here is below the tank. Bottom-up stereolithography 3D printer builds the part upside down.

The resin tank features a transparent bottom having a silicone coating. Laser light can pass through the coating but does not allow the cured resin to adhere to it.

The printer detaches the cured resin from the base of the tank after each layer. While at it, the platform advances upwards.

Bottom up SLA 3D Printing Illustration
bottom Up SLA 3D Printing Illustration

This process of detaching the cured resin is known as peeling step. Bottom-up SLA 3D printing systems are easier to make and operate.

But they have limited build size. The forces exerted on the component in the peeling step may lead to print failure.

Often, the bottom-up orientation find use in desktop stereolithography 3D printing systems.

Factors To Consider During Selection Of SLA 3D Printer

Here are fundamental considerations when choosing a stereolithography 3D printing machine;

Purpose

The intended purpose greatly influence the type of stereolithography 3D printer you need to buy.

Printer Style

There exist a few variety of printer designs available that you need to consider. Your choice dictates the type of SLA 3D printed parts you can produce.

Quality

You should assess the general quality of the stereolithography 3D printing system. Print speed and print resolution are the main parameters determining the print quality.

How Stereolithography 3D Printing Works

The 3 main steps in SLA 3D printing process are:

Step 1: Designing Parts For SLA 3D Printing

You can 3D scan data or utilize any CAD software to design your prototype.

Next, you should export the model using a 3D printable file format (OBJ or STL).

Remember, every stereolithography printer incorporates software to designate printing configurations. It also segments the digital prototype into layers for 3D printing.

After completing the setup, the print preparation program relays commands to the printer through a cable or wireless connection.

Step 2: Stereolithography 3D Printing

The SLA 3D printing process begins by the laser “drawing” the first print layer into the resin. Any place the laser beam strikes, the photosensitive resin solidifies.

A computer-controlled mirror helps in directing the laser to the right coordinates. After completing the first layer, the printer lifts the platform depending on the layer thickness.

In most cases, layer thickness is often around 0.1mm. Subsequently, the system permits additional resin to flow under the already-printed segment.

The laser beam then cures the subsequent cross-section. This operation repeats itself until completion of the entire 3D part.

You can reuse the resin not struck by the laser, which stays always stays within the vat.

Step 3: Post-Processing of SLA 3D Printed Part

You should rinse the part in isopropyl alcohol after completing the SLA 3D printing process. It eliminates any uncured resin.

After drying of the rinsed part, certain materials need post-curing. This process aids parts to attain their optimal strength and stability.

Ultimately, detach the supports from the components and sand the residual support marks. It ensures a clean finish.

You can easily paint, prime, machine and assemble SLA 3D printed parts for specific finishes or applications. Post-curing is vital for engineering resins.

Stereolithography 3Dprinting Process
Stereolithography 3Dprinting Process

It is also compulsory for certain jewelry and dentistry materials and applications.

Print Parameters Of Stereolithography 3D Printing Process

Most print specifications of SLA 3D printing systems are set by the manufacturer.

They are unchangeable. The only configurations are the part orientation (dictates support position) and layer height.

Part Orientation

Part orientation is a crucial print parameter for the designer. The variable relies on the type of stereolithography 3D printing machine.

Layer Height

In SLA 3D printing, the layer height varies between 25-100 microns. Lesser layer heights record curved geometries more precisely.

Even so, it increases cost, build time, and possibility of an unsuccessful print. The preferred layer height for popular applications is 100 microns.

Advantages Of Stereolithography 3D Printing Technology

Some of the main advantages of this technology include:

Uniform Strength

The SLA 3D printing technique produces parts with consistent properties throughout the model. Resin polymerization results in firm and uniform bonds throughout the material.

As a result, the mechanical characteristics of the part are predictable.

In contrast to fused deposition modeling components, an SLA printed part orientation does not affect its strength.

High Precision

Liquid resin curing is an exclusively photochemical process. The operation emits very little or no heat.

This component experiences no thermal expansion or contraction as a result. It produces an identical part to the original prototype.

The process maintains this precision layer after layer. As a result, it ensures precision throughout the 3D print.

Surface Finish

The most accurate SLA 3D printers can produce layers as thin as 25 microns. Basically, that is a quarter the thickness of standard writing paper.

The UV laser cures every specific point (Voxel). It results in a more precise reproduction of surface details comparable to the additive manufacturing procedure.

A stereolithography 3D printed part has a polished surface finish. It is similar to that of an injection molded part.

This is as a result of reduced layer thickness and surface features reproduction.

Specialty Materials

You can find numerous materials for stereolithography 3D printing available. There are low-cost SLA resins for DIY purposes and premium resins for industrial or specialized uses.

Each application requires a unique type of resin.

Moreover, SLA 3D printing application is widespread. This is due to SLA materials diversity from engineering grade resins, tough resins, wax resins, dental resins among others.

Disadvantages of Stereolithography 3D Printing

Some of the disadvantages of this printing technique include:

High Cost

SLA technology has a greater 3D printing cost than fused deposition modeling. Its resins are expensive, and much of it is wasted as support structures and residue.

They are also expensive due to the precision and high quality and precision of their parts.

Post-Processing

You cannot use SLA printed parts immediately after printing. Rather, you need to carry out considerable level of post-processing within SLA 3D printing operation.

All these post-processing activities consume additional resources and time. They also prolong the lead time of stereolithography 3D printed parts.

Expertise

SLA 3D printing technique is not the simplest to use.  Unlike FDM 3D printers, stereolithography printers need a specific degree of expertise and training to operate.

Applications Of Stereolithography 3D Printing

SLA 3D printed components have detailed features and polished surface finish. Therefore, SLA 3D printing is ideal for applications that need precision-built parts.

Manufacturing

Stereolithography 3D printed parts are perfect for investment casting applications.

The capacity to form tool-less patterns reduces the time needed for molds. This facilitates quicker production.

Moreover, the technique promotes low-volume casting and component prototyping possible. These substantial tooling and time saving are only practical due to SLA 3D printing technology.

Healthcare

Affordable, expert-level desktop SLA 3D printing assists doctors offer treatments. Gadgets customization offers effective service to every unique patient.

As a result, there have been great-impact medical applications. It also saves whilst saving institutions considerable costs and time from the laboratory to theatre.

Education

Stereolithography multipurpose tools for advanced research and immersive learning. The equipment can promote innovation and expose learners to expert-level technology.

While at it, it supports STEAM curricula in art, science, engineering and design.

Jewelry

The jewelry industry extensively applies stereolithography 3D printing technology. It develops sophisticated jewelry art pieces.

SLA 3D printed parts offer a high degree of detail. This enables jewelry makers to form complex designs.

Footwear

Stereolithography 3D printing process is popular in footwear industry. The industry employs SLA 3D printing technology to design and manufacture new shoe types.

Such footwear offer better performance than conventional shoes. The process of SLA 3D printing enables to customize every shoe, from the design to its material and application.

Entertainment

Entertainment industry uses HD physical models in prop making, character modeling, and sculpting.

The use of SLA 3D printed parts is prominent in bespoke costumes and video games. Stop-motion films and unique effects in blockbuster films also use this technology.

Dental Health

The application of SLA 3D printing in dentistry is mainly in the production of invisible aligners. Such aligners are substitutes to conventional metal braces.

aligners

SLA 3D printed prototypes help in oral surgery preparations. Orthodontists scan and print accurate 3D anatomical models.

It assists in efficient surgery preparation and simulation.

Product Design and Engineering

Rapid prototyping with stereolithography 3D printing enables conversion of ideas into practical proofs of concept. Engineers are capable of advancing these concepts to quality prototypes.

Such products resemble and function similar to end products.

Stereolithography 3D Printing Vs Fused Deposition Modeling (FDM)

In fused deposition modeling, you feed the filament via a hot extruder and deposition is layer-by-layer. FDM uses thermoplastics mixed with other materials, like carbon fiber, metal and wood.

This is one of the advantages of FDM over SLA 3D printing. The latter relies on a limited selection of materials.

In FDM technique, resolution implies the motors precision. Stereolithography, on the other hand, resolution is dependent on the laser beam tightness.

For this reason, SLA 3D printing technology can form parts of greater precision and detail.

Post-processing in FDM 3D printing entails detaching supports (if they are there) and polishing surfaces.

Fused Deposition Modelling
Fused Deposition Modelling

Conversely, in SLA 3D printing, post-processing involves dipping the part in isopropyl alcohol.

The essence is to eliminate excess resin.

You follow this by subjecting the stereolithography printed part to passive ultraviolet light. It enables additional strengthening.

However, the end product is generally not as tough as that from FDM process.

Also, the materials cost in FDM is lesser because the printers are inexpensive. Additionally, plastic reels are more affordable than resin.

Opt for SLA 3D printing technique when your priorities are smooth finish and high precision. Where cost and longevity is your concern, go for fused deposition modeling 3D printing method.

Stereolithography 3D Printing Vs Selective Laser Sintering (SLS)

Selective laser sintering utilizes a laser. It entails a completely different approach and is much more powerful.

The reason for this is rather than curing a part.  Laser beam heats up a powder until it fuses its particles tighter.

SLS are selective laser melting and direct metal laser sintering. They are particularly suitable for metals.

Selective Laser Sinthering
Selective Laser Sinthering

Normal SLS uses polymers such as nylon. Parts made through selective laser sintering are strong and durable.

Additionally, SLS creates 3D prints of intricate geometries.

The reason is that the process does not require supports. Also, detailing can be modestly high in SLS 3D printing.

But it typically cannot compare to the accuracy of stereolithography 3D printing.

SLS machines integrate highly advanced technology due to their powered lasers.  They including unique shielding against dangerous UV radiation.

It makes the SLS 3D printers are costlier with few desktop options available.  Moreover, SLS powders cost more than liquid photopolymers.

Simply choose SLS 3D printing if complex geometries, high mechanical are your concern. Also, cost should not matter.

Conclusion

As you can see Stereolithography plays an integral role in modern manufacturing processes. Therefore, it is critical you understand every aspect before adopting the technique in any plastic fabrication.

More Resources:

Stereolithography Process

Vat photopolymerisation

3D Printing On Plastic

 

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