Change from mm to inches when exporting as STL

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Change from mm to inches when exporting as STL

Postby Rusty » Mon Jul 01, 2019 1:25 pm

Greetings All,

Did all the designing using inch dimensions. Verified.
Exported project as STL.
Opened up project in a 3d printer slicer program and discovered that the size has been reduced/changed because the project seems to be now in MM.
How do I make sure that my project gets exported as an STL in inches, not mm?

Thanks to all that reply,
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Re: Change from mm to inches when exporting as STL

Postby garylmast » Mon Jul 01, 2019 1:30 pm

If your job setup is in inches the STL will export in inches and visa-versa. If you want it the other way around, after you accept the job setup, go back into it and change it to mm or inches and close it. It will automatically change the size of everything to the new value.

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Re: Change from mm to inches when exporting as STL

Postby Rusty » Mon Jul 01, 2019 1:51 pm

Thanks @garylmast, greatly appreciated for the quick reply.

Very odd, I changed my material setup from inches to mm, then re-exported as STL, opened the new file up in my 3d printer slicer program and everything seems to be in the right proportions, all good. Printing will confirm this.

So, why did it not export the STL file in inches when everything was identified in inches?

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Re: Change from mm to inches when exporting as STL

Postby TReischl » Mon Jul 01, 2019 2:01 pm

Rusty wrote:So, why did it not export the STL file in inches when everything was identified in inches?

Rusty


I am pretty sure that the STL importer works in units, not inches or mm. It threw me for a while too because there are those little inch/mm buttons, etc. At first I thought I was supposed to use those to tell it which units were being used. Nowadays I ignore them and just type in the size I want the object to be in inches because I work in inches most of the time.
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Re: Change from mm to inches when exporting as STL

Postby Adrian » Mon Jul 01, 2019 2:02 pm

Are you sure it's not the slicer program that is the issue? Maybe it's set to mm as a default and if you import something that is 6 inches it's assuming it's 6mm? My slicer program recognises exported STL files in either format correctly prompting me to convert if it's not metric.
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Re: Change from mm to inches when exporting as STL

Postby StuC » Mon Jul 01, 2019 2:12 pm

Hi Rusty,

STL files contain no units or scale, just raw X,Y,Z values. This means that it will be read in as whatever unit values the opening program is using and when exported Aspire will just put the raw values into the file. This is why when importing a STL model into Aspire there is the option to set the units so we can scale things appropriately as this information isn't contained within the file. If your 3d printer software only expects mm input and has no way to scale a file from inches then a mm model needs to be used for the job to make sure the raw values in the file are what your 3d printing software is expecting.

Hope that helps to clarify,
Stu

(as others have indicated whilst I was typing this :) )
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Re: Change from mm to inches when exporting as STL

Postby Rusty » Mon Jul 01, 2019 2:21 pm

Thanks to All, for the replies.

I will re-read all your comments to make sure I understand the process.

What was throwing me off is that I create inch models in Fusion 360, export as STL, and my slicer program recognizes that, no problem, no converting.

If Aspires "exporting as STL" function prefers mm then I will just design/model in mm.

Thanks again All for the quick replies.

I am trying to learn the modeling side of Aspire to use with both my cnc router and the 3d printer.
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Re: Change from mm to inches when exporting as STL

Postby Adrian » Mon Jul 01, 2019 2:35 pm

Rusty wrote:What was throwing me off is that I create inch models in Fusion 360, export as STL, and my slicer program recognizes that, no problem, no converting.

Are you exporting models the same sort of size from Fusion 360 as you are from Aspire though? After a bit of experimenting my slicer program "recognises" a model in inches by the fact that it's either very small or very large if the units were in metric and prompts me if it thinks I need to convert.
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Re: Change from mm to inches when exporting as STL

Postby StuC » Mon Jul 01, 2019 3:09 pm

Hi Rusty,

Aspires Export to STL function has no preference for units, it just exports as whatever units the user has chosen to create the job in. This appears to be the same behaviour as Fusion. When you mentioned exporting to your slicer program from an inch model in Fusion, are you just saving the STL file out, or sending it to your slicer program directly. There is a bug in Fusion where it would convert inch models incorrectly to mm when it was sending to an open slicer program, see the last post here:
https://forums.autodesk.com/t5/fusion-3 ... -p/6414039

However this, as shown in that thread, is a bug and not the expected behaviour. The expected behaviour in Fusion is to use the document units when exporting to STL which is the same process Aspire uses.

Maybe the above bug might be why you have been seeing differences?
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Re: Change from mm to inches when exporting as STL

Postby Rusty » Mon Jul 01, 2019 5:22 pm

Thanks again All,

I was only using F360 as a comparison. When I design in F360 I export as a STL, I do not go thru the 3d print save function. From the saved STL I then load into the slicer program. What ever design units I choose, they come thru perfectly to be correctly uploaded to the slicer program.

I just tried to scale my file, in mm, in the slicer program and was able to scale up to the actual size (converting the inch to mm).

In Aspire if I design in mm and export as STL the file is the right size in the slicer program.
So, not sure why the inch units do not reflect the true size.
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Re: Change from mm to inches when exporting as STL

Postby fixtureman » Tue Jul 02, 2019 11:00 am

On my laser software it sees everything in MM so I have to export my files from Aspire in MM to get the correct size. I design in inches and then go to job size and position and change to mm then export it
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Re: Change from mm to inches when exporting as STL

Postby Rusty » Tue Jul 02, 2019 2:36 pm

Thanks, @fixtureman.
I tried your procedure and that is what I need to do moving forward.
In Canada metric and imperial are both used, but I am from the old world, so I prefer imperial.
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