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.


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


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

Continue reading

INDUSTRY SPOTLIGHT: 3D Printing for Production Parts Gains Credibility

Why are some engineers so hesitant to use 3D printing for more than just development?

Engineers are hardwired and trained to make calculated decisions based on facts. Traditional manufacturing processes such as casting and molding have been around a very, very long time—since the Bronze Age—and time has perfected these processes and brought them to what they are today. Both industry experts and novices alike can benefit from hundreds of years of this process evolution. 3D printing processes are relatively new, especially when compared to casting or injection molding.

Motor mounts are among a growing list of automotive parts that are now manufactured using commercial-grade 3D printing.

Modern, commercial-grade printing equipment and processes are capable of predictable results that will ease the mind of the most skeptical engineer. DMLS (direct metal laser sintering) can produce repeatable results for parts that can be manufactured in no other known method. Proto Labs’ 3DP facility is not only ISO 9001:2008, but also AS 9100. This is the supplemental requirement established by the aerospace industry to satisfy DOD, NASA, and FAA quality requirements. This certification should give any engineer a sense of security.

Understanding some basic quality parameters around the processes can help to lay a foundation of credibility. For example, limits are set to the number of times base material can be used, or only virgin powder could be specified. This is no different than controlling the amount of allowable regrind into a plastic injection-molded part.

Rolls-Royce is a notable automaker now using commercial-grade 3D printing for some production parts.

Testing parts to confirm material properties are extremely common in DMLS. Building a standard tensile bar with each build is a great way to confirm batches of production are producing the desired results. This way the first batch can have destructive testing on the tensile bar and parts to confirm the material and process are producing parts with the specified properties. The future batches can test the tensile bar for confirmation the predictable results were achieved.

The aerospace industry has been embracing advanced manufacturing methods for some time now and the automotive industry has also been making great strides in this area. For example, recent articles have been published around the Rolls-Royce Phantom’s printed parts and BMW’s leading spot in adopting printing technologies.

INDUSTRY SPOTLIGHT: Commercial 3D Printing for Production Parts

Technology in the 3D printing space is advancing at the speed of light—everything from support structure software to material options and properties to ever improving processes. Some simply take these advancements as small steps in the overall progress of 3D printing, but these improvements are significant attributes that add value across industries and applications. 

Nylon handheld device 3D printed with SLS.

Medical and Health Care Development
Industries are adopting this technology for varying applications at very different paces. The health care industry has embraced nearly all forms of printing, but has particularly grasped onto direct metal laser sintering (DMLS). As we discussed last month, DMLS has a solid advantage over other 3D printing processes since it produces functional, production-quality parts from metal powder.  When plastics are concerned, selective laser sintering (SLS) is another additive manufacturing process with production in mind.

Product developers, designers and engineers in the medical and health care industries use many different types of 3D printing technologies, but why?

  • concept modeling and prototyping during early phases of product and device development
  • iterating design often to get parts in hand fast
  • reducing financial and design risks
  • building high-quality assemblies for end users to evaluate and influence human factor designs

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.

Continue reading

HP Selects Proto Labs to Test New 3D Printing Technology

HP Inc. made its announcement Tuesday morning at RAPID, the 3D printing trade show underway this week in Orlando. Here’s a glimpse of HP’s booth at RAPID.

Proto Labs has been selected by HP Inc. as a product testing site for the printing and PC giant’s new HP Multi Jet Fusion technology for industrial-grade 3D printing.

HP announced its new technology today at RAPID, a 3D printing and additive manufacturing trade show underway in Orlando, Florida through May 19. Proto Labs is at RAPID. You can find us at booth #443 to talk with a customer service engineer about our industrial-grade 3D printing services.

We’re excited to test drive this new technology that looks to be a dramatic leap ahead in 3D printing. We are looking forward to collaborating with HP on this new platform that promises to be faster and more economical than currently available 3D printing options.

Proto Labs’ staffers take a short photo break during RAPID underway all week in Orlando. From left, Joe Cretella, Greg Thompson, Rob Connelly and Thomas Davis. Visit Proto Labs at booth #443.

Proto Labs is one of several companies HP is working with as part of the company’s Early Customer Engagement Program, which conducts product testing and garners user feedback.

We were chosen because of our extensive experience as a prime user of industrial-grade 3D printing technology (also known as additive manufacturing) for our prototyping and low-volume manufacturing services.