Export STL is the wrong size

[Anonymous]

Hi All,

I am experience a strange behavior in fusion 360. When I export to a STL file when the units are in inch the corresponding part in the STL file is not sized correctly.   Changing the units to mm and exporting the same body to a STL results in a correctly sized part in the STL file.

Changing the units back to inch again and exporting a STL again results in a file with the part being to small.

I also have problems importing mesh (STL) files. I have to play with the default units to get the part to be the correct size.

Regards,

[kush.sharma]

Can you provide the exact steps to reproduce this issue and sample stl body with it? There are some known issues with scaling in mesh but it would help us fix faster if you can provide your workflow too.

[Anonymous]

Sure. I right click on the body or component and click "Save as STL". I use all the default STL settings. I change the units under the browser "Units". I've attached two STL files of the same component that was saved as an STL. The difference being the units, either inch or mm. The inch STL is a fraction of the correct size.

Thanks for your help. 

[HughesTooling · Accepted solution]

STL files don't contain unit information so if you export from Fusion in inches you need to make sure the program opening the file knows the file's in inches. Here's your 2 files inmported into Rhino into a file set to mm. The inch file is 25.4 time smaller, this is correct behaviour.

Mark

[Anonymous]

Thanks. I didn't know STL files didn't inherently have units.

[shdwlynx]

Since the Export STL function is now (in 2020) called Make->3D Print, this is now not a generic export function but rather a function to specifically supply an STL for a slicer, nearly all of which expect millimeters (mm) only.

The Send to 3D Print Utility function already automatically converts drawings that are in inches so that they appear in the slicer software in millimeters instead.  This same automatic conversion from inches to millimeters should also occur when exporting to an STL file (which will prevent thousands of wasteful Internet searches to find this very conversation).

If this is not the correct place to submit bug fixes / feature suggestions, please let me know where I should post this instead.  For anyone else reading this, please add your support to this post (or to whatever page I link this to should I be informed of the proper place for bug tracking).

[etfrench]

The proper place for the bug fix(es) is in the 3d printer slicer programs.

[shdwlynx]

How can it be the fault of the slicers if the de facto standard units for
STLs is millimeters? Why should Fusion 360 spit out files with very
different relative dimensions depending on which units you choose to use!?

[etfrench]

Stl files are unitless.  There is no de-facto standard.  Slicer software should allow the user to select the units.  Why should Fusion 360 output files in units which have not been selected?  It's a simple matter to select the desired units in Fusion 360, so the odds of this UI changing are rather remote.

[shdwlynx]

OK, let’s say that there is no de facto standard (even though there clearly
is based on the fact that all of the most popular slicers assume
millimeters). In that case, Fusion 360 should ask what units to base the
STL output on, rather than assuming that the units are not important. If
you design something in inches and know you’re going to use software to
consume the STL that assumes millimeters, then it makes sense to be able to
have Fusion 360 handle that conversion. Otherwise, we have to remember
that the consuming software assumes millimeters and change our drawing’s
units, export the STL, and change them back again. This is not an extreme
hardship by any measure, but it is a silly one since it can be so easily
overcome.

Ideally, the interface should look like this:

Units:
( ) auto – same unit as the design
(o) mm – default for most slicers
( ) inches

[etfrench]

Have you attempted to contact your slicer company to tell them to get out of the stone age and support better 3d modeling file formats?

[shdwlynx]

Sure, I’ll tell Utilimaker, Repetier, and all the other big slicers. What
new format should I recommend to them?

[etfrench]

Step.  I'll expect you to report back on what they say.

[shdwlynx]

Step, got it.

[dmichael.wagner]

It seems this is still an issue 5 years later as I can export a file as an stl and a step however they are significantly different and not with all models.  I create all models using inches however 99% of my exports regardless if its an stl or step file are the same size in my slicing software.  I am having this issue with a file where the stl is a fraction of the size compared to the step file.  Sure I can scale it up however I don't feel I should have to and I agree with shdwlynx that this is a Fusion issue.  The comment that "most slicers" assume MM and there for it is a slicer issue.  Two problems "most" and "assume", most does not mean all and I learned from Benny Hill that when you break down the word ass-u-me...

This is a Fusion issue that Autodesk should address.

[TheCADWhisperer]

@dmichael.wagner 

Can you Attach a *.f3d file here that Exports as the wrong size in stl?

[dmichael.wagner]

I'm not sure what a .f3d file is or where it is generated.

[TheCADWhisperer]

@dmichael.wagner 

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

[dmichael.wagner]

I ended up copying all components into a new file which seemed to eliminate the issue however I don't know why or what caused the original issue.  Having said that, I don't have the original so the file requested wouldn't have the same properties, assuming.