There are six technologies suitable for rapid prototyping and mass production projects. Of the six, "additive manufacturing," aka 3D printing, offers project managers and manufacturers the most flexibility regarding production volume and product design adjustment.

3D printing comprises two primary methods, Selective Laser Sintering (SLS) and Stereolithography (SLA), which offer engineering-grade component development. This post takes a deep dive into these two 3D printing methods. We'll look at their differences and compatibility with rapid prototyping and mass production projects.

Selective Laser Sintering (SLS)

Let's start with SLS. This 3D printing system utilizes a powder-bed, fusion additive manufacturing process. The laser in the device sinters layers of parts using a material-based powder bed.

After producing each layer, the roller lays out the next powder layer, repeating the process layer by layer until the project is finished.

After construction, the operator manually removes the finished component, bead blasting it in the post-production phase.

Stereolithography (SLA)

This process utilizes a laser to bounce ultraviolet (UV) light beams off reflective mirrors. The Galvo Motor System in the device steers the beam across the component's surface.

The laser starts by drawing layers of support structures, followed by the component geometry. The UV light cures each layer of the thermoset liquid resin before moving on to the next.

The operator utilizes a solvent post-manufacturing process to remove additional resin before removing the support structures.

Analyzing the Right Choice for Rapid Prototyping Needs

Common industry applications for SLA-manufactured parts include the construction of cosmetic prototypes featuring large parts, smooth surface finishes, and components requiring intricate details and high dimensional accuracy.

If your components require durability, SLS is the better manufacturing process for the project. SLS constructs accurate, functional prototypes quickly. There's an important consideration to bear in mind with SLS. No support structures are required, allowing the inclusion of multiple components in a single build. It offers a highly economical solution for high-volume production of parts.

SLA and SLS – Production Materials

SLA manufacturing materials are liquid thermoset resins known as photopolymers. SLA offers manufacturers and prototype designers the widest selection of printable plastic materials with an array of physical properties.

Some thermoplastic materials include the following.

• ABS-like.
• Polycarbonate-like.
• Polypropylene-like.

SLS printing materials are thermoplastic powders. Comparing them to SLA liquid resins, SLS materials are suitable for building durable end-user components. Some options for SLS materials include the following.

• Filled materials such as PA12 40% Glass-filled and PA12 Mineral-filled.
• Multi-purpose nylons like PA 12 White and PA 11 Black.
• Specialty materials like polypropylene natural and TPU 70-A.

Surface Finishes for SLA & SLS Components

Typically, components manufactured with SLA processes offer a smoother surface finish compared to those made with SLS. There are four finishes available. Let's look into each of them in detail.

Unfinished – There are remnants of the supports on the base of the component in the shape of dots. This finish is the better choice for cost-efficiency in manufacturing prototypes, larger volumes, or when fast lead time is a priority.

Sanded – The support structure remnants are sanded, eliminating nibs or dots.

Blasting – The operator sands the support remnants and finely blasts the part. Noticeable payers are still present in the finished part.

Custom – Clear finishing, soft-touch painting or paint, color matching, painting, textures, masking, and graphics or decals are available.

The surface finish of SLS components is usually rougher. However, they're more durable and suited for chemical or heat resistance. SLS works well for applications requiring dimensional stability or flexibility where needed.

SLA or SLS? – Final Considerations

Considerations like resolution, durability, and component size determine whether your process requires SLS or SLA printing. Here are some of the factors that may sway your decision on which technology best suits your needs.

• Surface Finishes – SLA offers a high-quality finish on printed components, producing a smoother finish than SLS after manufacturing. They look similar to injection molded components.
• Strength & Durability – Typically, SLS builds high-strength, durable components due to its use of engineering-grade plastic materials.
• Resolution – SLA offers higher resolution than SLS. You usually have three options for resolution to balance surface finish quality and detail with cost.
• Component Size – SLA printers have larger build envelopes than SLS printers.
• Production Tolerances – SLA produces tighter tolerances than SLS.
• Heat and Chemical & Heat Resistance – SLS thermoplastics offer better chemical and heat resistance than SLA components.
• Cost – SLS materials are significantly more expensive, ranging from $300 to $600 p/kg. SLA materials cost approximately $80 to $100 per liter.

SLA or SLS – Which Is Better?

There's a trade-off between using SLS and SLA printing for your projects. Some rapid prototyping projects may require a combination of SLA and SLS parts to reduce costs while maintaining optimal surface finishes where required.

The choice of which 3D printing solution best suits your project depends on your requirements and budget. A skilled and reputable manufacturing partner can advise you on the right process for your project.