Even though GrabCAD Print has been able to directly import engineering CAD files for about 3 years now, a recent survey of our customers revealed that nearly 52% still use STLs to 3D print, not native files from SOLIDWORKS, Inventor, Creo or CATIA.

Which is fine, a lot of other 3D printers still don’t have the option to import anything besides STLs or 3MFs, but I just wanted to write a quick something to give that 52% a reason to give native CAD another look. So let me present: 5 Reasons You Shouldn’t Use STLs for 3D Printing (Anymore)

Reason #1: You Lose Resolution

So we all know that STLs are thousands of touching triangles, versus native engineering CAD files, which are defined mathematically:

Think of that hole in the middle here- on the CAD file, it will be perfectly defined as a mathematical, geometric circle, but in the STL, you’ll have a sort of ‘stop-sign’ tessellation effect, depending on the resolution you exported at:

And even worse than that, once someone gives me an STL, I can’t ‘enhance’ the resolution in any way, but I can always convert the CAD file at higher and higher resolutions, with a simple slider in my CAD package.

Of course, 3D printing is a finite process, so after going above a certain resolution, it doesn’t matter to the 3D printer, the print will look the same. But as experienced operators will tell you, the first time a large group of people try to export STLs for printing, many of them will use a too low STL resolution and make their part tessellated, and many will use too high a resolution and make their file size huge.

So why not avoid all that hassle and just work with the CAD data when you can, letting GrabCAD Print’s internal slicer decide what resolution is best?

Reason #2: You Lose Color

Now, I have heard rumors of ‘color STLs’ from time to time, and the new-ish 3MF format does support exporting face and body colors, which is nice. For full color printing of textures and logos I still use VRMLs and OBJs, but CAD files can export body colors into GrabCAD Print, and you can do a surprising amount with just those, with no extra effort.

You know what, here’s a chart to show what I mean:

Of course, you can re-apply body colors to an STL in GrabCAD Print, (see my tutorial here) but why apply them in your engineering CAD system, only to lose them by going to STLs, and then have to apply them all again? Native CAD import solves that.

Reason #3: You Lose Editability

It’s 4:55 on a Friday. You’re about to hit ‘go’ on that big, over-the-weekend print. And that’s when you notice it.

The hole in this engineer’s file is 0.18” inches too far to the left. And he’s already gone home for the week. And all you have is their STL.

Which position would you rather be in: having an STL that you can’t really edit, or being able to open SOLIDWORKS to do this, in under 1 minute:

Even with neutral formats like STEP files, face manipulation like this was one of my go-to tricks when I worked in CAD tech support and had to get a job done fast. (And it was getting close to quitting time.)

STL files don’t have that wealth of smooth, mathematical faces to select to make those commands happen, they have thousands of smaller facets that are harder to select and edit. (If your CAD package and graphics card can even open an STL with 30,000 faces.) STL editing can still be done, but it’s much, much harder than history-based, parametric CAD files.

Reason #4: You Lose Advanced Infill Control

About one year ago, GrabCAD Print introduced new infill features which allowed you to select a face in the software, and put extra FDM contours and material RIGHT THERE behind the face, and only there:

In fact, you can do this on ANY face in your CAD file if you wish:

This is how our best customers optimize their FDM printed parts for weight, strength, stiffness and cost all at the same time, by putting material ONLY where they need it!

But this advanced Infil control only works for CAD files, parasolids, STEP and IGES, not STLs, since STLs don’t have those clean faces. And finally:

Reason #5: You Lose TIME

Everyone knows CAD files are more versatile than STLs. And all busy printer operators will tell you: “Getting only STLs just saves time!” And it does.

If everything goes perfectly.

But the moment you’ve got an STL at the wrong resolution, or one where you didn’t know the color intent of the creator, or need to make some small edit on, or need to optimize the infill on, then you instantly flip to STLs requiring MORE time.

Even worse, it’s more time for you AND for your print requestors, since THEY have to export a new file, YOU have to intake a new file, and you have to compare it and check it, yada yada yada.

So, next time you’re training new engineers how to send you files for 3D printing, if you want to save them AND you time for the next 5 years, maybe ask for their direct CAD file and see what happens?

You may find even more than 5 reasons to like that better.