Stereolithography: Sorting Out Surface Finishes

Posted On May 25, 2017 By Tony Holtz

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 Protolabs, and when it makes sense to use each.

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.

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.

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.

A standard finish is applied after support surfaces have been sanded in the natural finish stages and the part undergoes a fine grit blast—this provides a uniform look and soft, frosted appearance. The part has less clarity, but best appearance. When should a standard finish be selected?

  • When a uniform finish is required
  • When part clarity is less important

With all three surface finishes—unfinished, natural, standard—you will see very minimal cost differences, so it really comes down to cosmetic requirements and part functionality.


But wait, there’s another option! If you require a part with more detail or elevated level of cosmetic appearance, custom finishing is available. This is great for when you need 3D-printed parts to resemble injection-molded parts, highly cosmetic parts to show to potential customers or colleagues, for concept modeling, or for marketing purposes. One consideration that should be made when requesting a custom finish, however, is that it may impact lead time and part cost.

There are multiple custom finishing options:

  • Soft-touch paint
  • Clear part finishing
  • Paint
  • Decals
  • Texture

If you have any further questions regarding stereolithography or surface finishes for 3D printing, please visit or contact one of our application engineers at 877-479-3680 or [email protected].