Exporting an STL file writes inches as mm?

[weshowe]

I think this behavior has changed with the current release. Previously, if I modeled in inches, Fusion saved an STL file such that CURA interpreted an inch to be an inch. I don't really know whether that is specified in the file or if Fusion automatically scaled the body, it just worked.

Now, a 1 inch model comes in as one millimeter. There is an obvious workaround (25.4x) that I applied and, of course, that works and I can move on with my project. I double-checked my units (in) and used the measure tool to confirm what I made was the size I wanted.

Perhaps I changed something, but I would really rather have Fusion work like it used to. Millimeters is the native size for the 3D printer, and sometimes I model in millimeters, but this old dog still thinks in inches, so much of what I make is my default inch sizes.

Is this a bug, a change, or am I doing something wrong?

[weshowe]

At the expensive of looking like I am talking to myself here, I found the root of why I thought the behavior changed, in fact it may not have:

When you export to 3D utility (Meshmixer) either Fusion or Meshmixer converts the size from inches to millimeters. When you just write an STL file, whether from the Make menu or by right clicking on the body menu, no conversion is applied. Since I don't usually need help making support structures, I started just going straight to STL files.

I would think from a consistent behavior standpoint, applying a units conversion no matter what would be how Fusion should act. When I want to output millimeters, I can set my units to millimeters.

So it appears this isn't a bug, but perhaps someone at AD can look at whether this could be changed in a future release.

 - Wes

[Anonymous]

I just had this happen to me after a Fusion update last week. I just started using Fusion 360 and inches would output to inches in the .stl but now it doesn't and the .stl converted inches to mm. I joined the Forum and searched for my problem and I'm surprised your post is from June last year.

Perhaps it was corrected and then lost in the last update?

[weshowe]

I was recently reminded of this post. Further research I did after I made it indicates there is no place in the STL file itself that specifies units (inch, mm, cm, etc.). Just numerical coordinates. The slicer you are using would have to be set to have the same units, and Slic3r and Cura do not seem to have any option to do that. Simplify3D has a function that scales inches to mm, but it has to be manually applied on every file.

The best option, IMO, is to just create your models in mm, or if they are already created to change the scale for the file and save it. I don't think this is Fusion's fault, just a loose file specification. Working in millimeters is not so hard to learn and has saved me from many frustrations.

[HughesTooling]

From my tests if you use Save As STL within Fusion, enable Send to 3D Print Utility, set to Custom and select your slicer the export will be scaled to mm. I've tested a few slicers and they all seem to expect the STL to be in mm.

If you just want to export and save the STL without sending it to your slicer just change the Document Settings, Units to mm and export. After export just change them back to whatever they were before. The Unit setting is in the browser under Document Settings.

I did find a bug I'm not sure's been fixed but if you use the first option above and save directly to your slicer then try using the second option above the scale can be wrong. The only way to fix this is to close Fusion and restart.

If you are exporting from the cloud the export will be size for size so in a mm design 1mm will be one unit and in an inch design 1 inch will be 1 unit. So if you export an inch design from the cloud and import into most slicers you'll need to scale up by 25.4.

Mark

[TheCADWhisperer]

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@weshowe wrote:

…. or if they are already created to change the scale for the file and save it. …. 

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No need to change the scale.

I have 2 dozen different printers.

Software for some allows changing the units - others do not.

I have simply gotten into the habit that if I am working in inches - I set the units to mm before save as stl and then set back to inches if needed.  No scaling required.  Works flawlessly.

[lichtzeichenanlage]

Just for the protocol. STL files are exported as units. If the document in Fusion 360 is set to mm 1 unit equals 1mm. If it set to inch it is inch and if it set to miles guess what... yes a unit is a mile 😉

So scaling is not need, you just have to know what unit means...

[karina.harper]

As an update to this old thread:

After some research we found that having Cura open or sending a file to Cura from Fusion results in a file being translated to mm before being written as an .stl.

Normally, Fusion should export the value of the size, not changing the units at all.

e.g. a 1 inch cube would be exported as 1 x 1 x 1 and would enter into any other software unitless. With Cura open, a 1 inch cube will be written as 25.4 x 25.4 x 25.4 

This has been logged internally (FUS-46804) and will be worked on by the devs.