TIPS WITH TONY: Behind the Scenes with File Formats

Why can’t you read my CAD file? Wrong file format? What formats do you accept? In our latest tip, I’ll cover what file formats work best with each manufacturing service at Proto Labs and discuss common questions that occur.

Simply put, we accept several different file formats, but some work better than others. To begin, here’s our list of formats that can be uploaded to our website:

CAD Programs:

  • Solidworks (.sldprt)
  • Autodesk Inventor (.ipt)
  • AutoCad (3D .dwg)
  • PTC ProE/Creo (.prt)
  • CATIA (.catpart)
  • SpaceClaim (.scdoc)
  • SketchUp (.skp)

Neutral File Formats:

  • IGES
  • STEP
  • ASIS (.sat)
  • Stereolithography (.stl) — only available for additive and machining

Proprietary Software
We use proprietary software that is able to read or translate the file formats above. If you submit a format not listed, you’ll receive a no-quote and will need to upload a new file from the list of approved file formats in order to receive a quote. But if you submit a file from the list and you still receive a no-quote, there is a good possibility that the file was either corrupt or unable to be translated properly. In this case, we would suggest trying another file format, or multiple file formats, so we have options for translation. Or, reach out to one of our customer service engineers at or 877.479.3680 to discuss a solution.

Injection Molding
Our software is able to read a majority of file formats for injection-molded parts but we suggest uploading a CAD with only the features you would like molded. Internal faces and multiple part files are difficult to read or translate, which run the risk receiving a no-quote or having the wrong features molded. We’ve found that exporting IGES or STEP files work best as much of the information within the CAD is not exported, leaving you with only the geometry intended for injection molding.

The lone file format not accepted for injection molding is Stereolithography (.stl). An .stl file is constructed of small, triangular faces that create much larger surfaces whereas a neutral CAD file will have a much smoother surface that comprises the part’s geometry.

The illustration depicts a sphere modeled as the native file format of a CAD program versus an .stl file. The red dotted lines show how the part would appear smooth in the native CAD format and the black triangular faces show how the part would appear jagged in a model designed as an .stl file.

CNC Machining
We accept all previously mentioned file formats for CNC machining, regardless of whether it’s a milled or turned part. Our automated toolpathing software can define the direction for machining or we can manually manipulate the surfaces for improved toolpathing with all but one file format — you guessed it, .stl files. This format is acceptable, although manual positioning for machining is not possible and left to our automation. It’s very important to note that threaded features are also unsupported in the .stl file format. All other formats are possible for threading as long as they follow our guidelines for threaded holes. We suggest that whenever you are able to provide a file other than .stl for machined parts, please do so.

A comparison between a 3D CAD model designed as an IGES file (left) versus and .stl file (right).

Additive Manufacturing
Additive manufacturing (3D printing) can produce cosmetically pleasing parts as well, but unlike its machining and molding counterparts, our old friend .stl is the preferred file format. All formats submitted in native CAD or neutral file formats are translated into .stl in order for our additive machines to properly produce parts.

Another advantage of the .stl file format in 3D printing is that you can typically receive an instant quote; on occasion, a manual quote may be required but this is still typically sent to you within a few hours. Instant quotes are available for stereolithography (SL) and selective laser sintering (SLS); Direct metal laser sintering (DMLS) also uses an .stl format, but more processing is required so a manual quote is always sent. Although all file formats can be submitted, we would suggest submitting a .stl file format whenever possible for parts that are 3D printed.

For more information on file formats or to receive a quote, please visit our website at or contact one of our customer service engineers with additional questions on any of our services.

This entry was posted in Tips with Tony and tagged , by Tony Holtz. Bookmark the permalink.

About Tony Holtz

Tony is a technical specialist at Proto Labs with more than 10 years of experience ranging from CNC mill operator to mold designer to customer service engineer. While his formal education is in industrial machinery operations, he has extensive knowledge and experience in both traditional and advanced manufacturing processes and materials. Throughout his tenure at Proto Labs, Tony has worked with countless designers, engineers and product developers to improve the manufacturability of their parts.

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