What is SLA Printing? | The Finest Guide

What is SLA Printing?

SLA Printing, better known as STEREOLITHOGRAPHY, is a high-profile 3D printing and additive manufacturing method utilizing a computer-programmed laser beam to shape the desired product.

SLA is attributed as one of the most popular 3D printing methods globally because of its rapid manufacturing speed. Under ideal circumstances, SLA can produce rapid prototypes, high-end concept models, and parts with complex geometries with high accuracy and isotropic properties in as quickly as one day.

In this guide, I’ll try my best to include all the necessary information related to the SLA 3D printing technique. 

SLA  is capable of manufacturing components with good features and a smooth surface finish. In outline, the method transforms the photosynthetic resin into solid-state layer-by-layer through photopolymerization.

How does SLA Printing work?

• Software
• SLA 3D Printing
• Post Processing 
• Alternate method

Software

SLA comes with a CAD software mechanism that helps in designing a digital version of the product. The CAD files must be converted to STL files (if it doesn’t automatically). Standard tessellation language (STL) is a software format created specifically for stereolithography. It is critical in determining the surface geometry of the 3D object.

SLA 3D Printing

One should note that desktop SLA printers work upside-down. The stereolithography machine starts the process by drawing the layers for support structures, and the component, with a laser, pointed to the resin’s surface. The laser solidifies the resin present on the build surface; it starts slow and increases in a controlled and incremented manner.

A layer starts to image on the resin surface; once the layer is completed, the build platform moves down, and the recoating bar moves across the platform to image the next layer of resin. The same process will be repeated layer-by-layer until the product is completed.

The resin which didn’t come in contact with the laser is kept in the vat and can be reused.

Post-Processing

After the polymerization is finished, the built platform comes out of the tank and ducts the excess resin. In the end, the part will be removed from the platform, washed and cleaned to culvert the excess resin, and then kept in a UV oven for final curing.

Post-print curing is often overlooked but is extremely crucial for making the part stronger and more stable in nature.

Alternate Method

There is a successor or progeny for SLA, and that is DLP (Digital Light Processing). DLP doesn’t use laser light but a digital projector screen to flash a single image across the build platform as it is a digital screen; each laser will be made from square pixels.

That makes the DLP printers’ resolution corresponds to the pixel size; on the other hand, it’s a laser spot size for SLA.

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SLA Printer Components 

SLA machine construction, Source - manufactur3dmag.com

All types of SLA printers are comprised of four sections; here are they:

1. A tank filled with the liquid photopolymer. The liquid resin is crystal clear in appearance.
2. A punctured platform submerged in a tank – The platform is placed very low in the tank and moved according to the printing process.
3. An ultraviolet laser
4. A computer program or interface which manages the laser and platform moments.

Advanatges and Disadvnatges of SLA 3D Printing 

Advantages

1. SLA’s precision and accuracy with product development make it one of the best in the 3D printing industry.
2. SLA is capable of the most acute tolerances for any additive manufacturing method – +/- 0.005″ (0.127 mm) for the first inch, and an additional 0.002″ for each additional inch.
3. Print surfaces cones with a smooth finish and aesthetic looks.
4. It makes high-quality products with detailed features like sharp corners and thin walls etc. Minimum feature size – 50 and 250 μm, layer thickness, go as low as 25 μm.

Disadvantages

1. High printing costs – the materials, equipment, machine, and other setting up costs a ton.
2. Rapid slope and overhang extensions need support structure; else, there is a possibility of the product’s potential collapse during printing or curing.
3. Limited offering in colors (black, get, and white) and materials. Resins are exclusive; thus, changing or switching them between printers becomes impossible.

Applications

SLA printing is widely used in several industries to create the state of the art products. Here are some examples:

Engineering and Product Design

Stereolithography adds tremendous value to engineering and product design. It manufactures custom tools, molds, and manufacturing aids at significantly lower costs and cycle times than conventional manufacturing. This creates significant improvements in labor productivity, defects, and assembly speed.

Healthcare

Affordable SLA printing will help doctors create unique solutions for individual patients leading to better-delivered treatments. It can evolve the entire healthcare ecosystem making treatments specific and cost-effective for both parties.

Dental

Dentistry can reap fantastic benefits from 3D printing. It will help create specific solutions for individual patients, such as custom teeth and custom appliances at every stage of the workflow to improve patient care.

Education

Here’s where things will become a bit more interesting as education as an industry has been struggling for years to bring innovative solutions to teach students the necessary skills. With the help of other 3D printing solutions, SLA printing can display students to newer and more formidable technologies and immerse them in creative and critical learning.

Audiology:

SLA printers can produce innovative audiology products with high quality and cost-effectiveness. The common applications are custom earplugs and earbuds, hearing protection, custom hearing aids, etc.

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Stereolithography Design Guidelines

SLA vs. SLS 

SLS (Selective laser sintering has a drastically different approach to producing products; however, it still utilizes a laser.

The laser in SLS is much more powerful than the SLA laser because instead of cutting the substance, the laser beam hits the powder on the build surface until it fuses to create the desired shape.

SLS prints are stronger, durable, and complex geometries( thanks to the fact that they don’t need support structures). On the other side, SLA print products are more precise in their design.

SLS printers are more expensive as they use high-powered lasers, leading to additional equipment incorporation like special shielding against harmful UV radiations. Even SLS powders are more expensive than photopolymers used in SLA.

Conclusively, if cost isn’t a barrier for you and your priority is mechanical strength and intricate shapes, then you should go for SLS. But, if you need precision in your parts, then SLA is the best bet.

Stereolithography Resins 

A quadcopter prototype 3D printed with SLA, Shoutout: FormLabs

There are several reasons for choosing the right resin for your applications. There are mainly five types of resins – Standard Resin, clear resin, engineering resin, dental resin, and castable resin.

Standard Resin: It is perfect for producing art models, ideal for concept modeling and rapid prototyping. Their low cost, injection molding, smooth finished parts, and high stiffness make them attractive to manufacturers.

The color of resin will create a substantial difference in the products. White color resin is specifically used for a smooth surface, and grey color resin is ideal for finer details.

Clear Resin: It is used for producing fluidic products, LED housing, and internal structures. The properties are quite similar to standard resin. However, it can be post-processed to achieve optical transparency. UV radiation might affect transparency in the long term.

Engineering Resin: There are two types of engineering resins – tough resin and durable resin. 

The tough resin can be attributed to materials like ABS used for resisting high-end stress and strain – Tensile strength: 55.7 MPa and elasticity 2.7 GPa. The resin will be used for shatter-resistant and rugged prototypes.

On the other side, the durable resin is resistant to wear, flexible, and has good mechanical properties similar to polypropylene. It is advisable to use this resin for consumer products, functional prototypes, and low-wear mechanical parts.

Dental Resin: As the name suggests, it is used in orthodontic and medical equipment. It is steam sterilized using an autoclave for direct use in the operating room. Its considerable resistance to fracture makes it ideal for surgical aids, appliances, medical arts, hard splints, retainers, etc.

Castable Resin: Castable resins are most compatible for producing jewelry and investment casting. It exhibits material with sharp details, a smooth finish, and fine lines. The production enables directly from a digital design to investment casting through a single 3D printed part.

The castable resin will also burn out quickly (less than 0.02 %)

Here’s a table showing their properties:

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Why Choose SLA for your 3D Printing Project?

In a Nutshell, SLA printing is a fantastic choice for rapid prototyping and manufacturing high-end, intricate designed models. It has the capability of manufacturing accurate, precise, innovative concept models.

FAQs

1. Which 3D printing method is faster? SLA or FDM?

Ans. In simple terms, SLA’s laser printing technique tends to be much slower than FDM. The lasers have a much smaller surface area. Therefore, it takes more time to cover each layer. Generally, SLA printing also has more post-processing steps than FDM. However, projector-based printing like DLP and LCD is even faster than FDM.

2. Which one is stronger: SLA or FDM?

Ans. In terms of mechanical performance and material strength, SLA resins stand no chance compared to FDM filaments. FDM materials like Nylon and polycarbonate are known for their toughness and rigidity. SLA resins generally are more expensive and yield fewer parts per unit of resin than FDM 3D printing filament spools.

3. What are SLA resins made of?

Ans. SLA printing uses liquid resins, which are made of photosensitive mixtures of monomers and oligomers – short chains of carbon molecules that are joined into longer chains during the photochemical process eventually to become hardened plastic.

4. Which are the top 5 3D printing Companies?

Ans. The top 5 3D Printing companies are:

1. 3D Systems Corp. (DDD)
2. Proto Labs Inc. (PRLB)
3. FARO Technologies Inc. (FARO)
4. Materialize NV (MTLS)
5. The ExOne Co. (XONE)

5. What are the common problems practicing while 3D printing?

Ans. Below are the common problems faced while practicing 3D printing:

1. Over-heating
2. Under-extrusion
3. Layer-shifting
4. Over-Extrusion
5. Gasp in the top layer
6. Not sticking to the bed
7. The printer is extruding the plastic at the beginning of the print

Suggested Read – 

• How to Cut Polycarbonate | A Complete Analysis
• What is UHMW Plastic Material? | The Definitive Guide
• 7 Types of Plastics | An Helpful Illustrated Guide
• Mechanical Properties of Plastic Materials | The Definitive Guide
• What are the Top 5 High Tensile Strength Plastics?
• Top 10 Injection Molding Materials (And Why They are the Best)
• Plastics Vs. Polymers | What are the Differences?
• What is PETG Material? | The Definitive Guide

Final Thoughts

That was my take on SLA printing. I believe it’s a technique that, used properly, can bloom great results for manufacturers. Stay tuned for more awesome posts posted every day.

Have a lovely week.

Peace Out.