Stereolithography

Image credit: ArtCorp

Stereolithography (SLA) is a 3D printing technology that uses ultraviolet light and photosensitive resins to produce parts.

Stereolithography based 3D printers have three main components:

Parts

1) a pool of resin (liquid plastic) that parts are built in,

2) A movable platform that is submerged in the pool of resin that parts are built on,

3) An ultraviolet (UV) light that can harden the resin to construct a part on top of the platform.

With Stereolithography 3D printers a model from a CAD program is turned into a series of cross section data. That data is transferred to the 3D printer and the process begins.

3D Printing

The platform starts out very close (0.05 mm) to the surface of the pool of resin. The UV light traces one cross section of the CAD data onto the surface of the resin hardening it and bonding it to the platform. The platform lowers by a fixed increment (which varies by manufacturer) into the pool of resin and the surface of the model is covered by fresh resin. The UV light then traces another cross section bonding it to the first. This process is repeated thousands of times (The number of repetitions depends on the height of the model being built) until a full model has been produced.

Finishing

When the process is complete, the platform is lifted out of the pool of resin and the part can be removed from the platform. Parts made using Stereolithography based 3D printers need to be washed to remove excess resin and often need to have support structures removed. Once washed, parts can be machined, sanded, painted, and other wise modified.

Pros

Benefits of Stereolithography

High resolution parts
Translucent materials
Complex parts can be produced

Cons

Drawbacks of Stereolithography

Expensive relative to other 3D printing technology
Requires some cleaning/finishing
In the stereolithography process parts that have dynamic shapes require support structures to be built. Ex. when printing a martini glass
the section that holds the liquid protrudes from the stem. To ensure the model is not deformed the 3D printer creates a support structure to support the model. When complete the structure can be removed
but it does impact the aesthetics of the part slightly.

Companies that Sell Stereolithography Equipment

Companies that Offer Stereolithography Services

FAQS

Why is it called “Stereolithography”?

The name “Stereolithography” can be misleading. Traditionally lithography meant printing on a stone (from the greek “Lithos”). However, the term “lithography” has been been adopted in the printing industry to describe any printing technology that relied on transferring ink to paper via an inscribed platform. The “Stereo” prefix suggests the dimensionality of this technology.

Why should I use Stereolithography instead of another 3D printing technology?

High level, use Stereolithography when you need high quality parts and aren’t focused on low cost.

Cost

Parts made with stereolithography can cost as little as $20 to many thousands, depending on the size and complexity of the part, the resolution required, and the time frame for production. Stereolithography is one of the more expensive 3D printing technologies.

Time

Parts can usually be made in 1-2 weeks and in days if your budget allows for rush fees. There are many service bureaus that allow you to upload parts, pay via credit card, and have the parts delivered to your home. There is little difference in production times between 3D printing technologies.

Scale

Stereolithography and other 3d printing techniques are generally used for rapid prototypes or in extremely small scale manufacturing for specialized industries. Because of the high surface finish of Stereolithographed parts they are often used as masters for urethane castings.

Use

Parts can be:
Used to test mechanical designs
Finished and painted to be used as models for presentations
Used as casting patterns for urethane or other casting processes

Quality

Parts made with a stereolithography 3D printer can be extremely high with translucent optical properties and smooth surface finishes. Parts made with stereolithography have mechanical properties close to engineering materials and are often used for mechanical testing.