Stereolithography: Sorting Out Surface Finishes

There are a number of factors—resolution, tolerance, material selection, surface finish—to consider when designing for the industrial 3D printing process of stereolithography (SL). For our latest tip, we’ll discuss the four stereolithography finishing options available at Proto Labs, and when it makes sense to use each.

Unfinished

Stereolithography (SL) technology uses a build platform that requires support structures for all features so they don’t float away or collapse during the build process. These support structures are removed after the build is complete, but they do leave visible markings on the part.

stereolithography proto labs

3D-printed parts are moved from the SL chamber after a build finishes. Supports are then removed, parts are UV cured, and a selected finish is applied.

In an unfinished state, after the support structures are removed, dots or nibs are noticeable where structures were attached to the part surfaces. So, when would leaving a part unfinished make the most sense?

  • When a clear part is desired with no custom finishing
  • If you have your own finishing capabilities, or have another shop that can perform post-build finishing
  • To achieve the best accuracy possible

Natural

A natural finish provides a surface finish that absent of dots or nibs, which leaves a more desirable cosmetic appearance. The surface is not as clear on the down-facing surfaces that had supporting structures, but the top surface would remain clear. When should you use a natural finish?

  • On small or delicate features that may be destroyed by additional finishing such as grit blasting
  • On clear parts where down-facing surfaces are not a cosmetic concern

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On-Demand Webinar: Designing for Stereolithography

Last week we kicked off our webinar series on designing for 3D printing. The first session focused on stereolithography (SL) and it’s available on-demand here.

Key Takeaways

  • Properties of commonly used stereolithography materials
  • The unique benefits of stereolithography such as feature resolution and recommended applications
  • General design tips for overhangs, support structures, finishes and more

Top Questions

Can you describe the resolution of SL parts in terms of microns?
There are 25 microns per 0.001 in. Normal resolution builds in 100 micron layers, high-resolution builds in 50 micron layers and micro-resolution builds in 25 micron layers.

The minimum X/Y resolution would be 250 microns in normal resolution, 100 microns in high-resolution and 50 microns in micro-resolution.

What’s the cost difference between normal- and high-resolution SL parts?
There’s no set number since it depends on the part’s geometry. But for parts under 1 in., customers will see a relatively low cost difference between normal- and high-resolutions.

Height is a primary driver of cost so once you start approaching 2 to 3 in. build heights it can start to differentiate more dramatically. But, with our instant quoting process it’s easy to compare these costs simply by clicking back and forth and comparing resolutions.

What’s the rule of thumb for wall thickness in hollow structures?
We try to stay above 0.03 in. and a general rule is 0.01 in. wall thickness per inch of the part. For example, a part that’s 8 in., you’ll want to shoot for 0.08 in. wall thickness for a well-supported hollow part.

More 3D printing webinars on the way…
The next webinar on our calendar will be on accelerating medical device development with rapid prototyping, which you can sign up for here. And, in the coming months we’ll have more 3D printing webinars that will focus on designing for selective laser sintering as well as direct metal laser sintering.

WEBINAR: Designing for Stereolithography

3D printing deserves an in-depth look. Whether it’s determining the right 3D printing process, selecting the right material or understanding design considerations, there’s a lot to think about.

Eric Utley, 3D printing application engineer

We’re kicking off a series of 3D printing webinars with each session focusing on one process so we can really take a close look at what makes each process unique.

Eric Utley, 3D printing application engineer at Proto Labs, will share:

  • An overview of stereolithography
  • Material options and recommended applications
  • Design tips to improve surface finish, reduce cost and other benefits

After the presentation, you’ll be able to ask Eric any questions you have in an open Q&A session.

TITLE: Designing for 3D Printing: Stereolithography
DATE: June 23 at 1 p.m. CDT
REGISTER: Click here to register and attend

Even if you can’t make it, you can still register and we’ll send you a recording and you can watch it on-demand.Also, feel free to forward this invite to your colleagues.

Q&A: Eric Utley Discusses the Advantages of Stereolithography

Eric Utley, application specialist at Proto Labs.

We’ve been 3D printing for a while now, and our facility in Raleigh, North Carolina is packed with 3D printing specialists. For this installment of our Q&A, we spoke with one of those experts, Eric Utley, application specialist, for a chat about stereolithography and why product designers and engineers need it for prototyping.

To start off, can you give a quick overview of the stereolithography (SL) process?
Stereolithography uses UV light shot from a laser to cure a liquid thermoset resin called a photopolymer. In fact, even though 3D printing is often thought of as a new technology, SL has been around since the 1980s. But there’s a reason it has stuck around for so long — it has some key features that product designers need for prototypes.

What are some of those key features unique to SL?
I’d say the most important feature is that it creates a very high-resolution part with excellent surface finishes.

It can handle micro-sized features so it’s most suitable for parts that have a high level of detail. Most SL parts will have a nice, smooth finish and, although it’s typically used for prototyping, it leaves you with the feel of a final part — and looks go along way when sharing your new product design.

Another important benefit of SL is that it’s our most flexible process in terms of geometry it can handle, which gives designers a lot of freedom to work with.

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NEW JOURNAL: Pitting Manufacturing Processes Against One Another

In the cover story of our current issue of the Proto Labs Journal, we pit manufacturing processes against one another.

As you know, the manufacturing industry is peppered with prototyping and production processes that share some common attributes, but also some notable differences. Our manufacturing “bouts” explore how several of these processes — big and small — compare. The fight card includes:

  • Magnesium Injection Molding vs. Magnesium Die Casting
  • Stereolithography vs. Fused Deposition Modeling
  • Direct Metal Laser Sintering vs. CNC Machining vs. Metal Injection Molding

Beyond our cover story, read about Sean Doan, a long-time Proto Labs employee who is the go-to person in our R & D division; the latest in innovation and advanced technology we’ve mined from the Internet; and new service offerings at Proto Labs.

Read the full Journal now.