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Export STL file dimension units issue - Export STL file causes all dimensions to scale approx 2.5x (units issue?)
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RustyL  
#1 Posted : Wednesday, March 16, 2016 5:02:53 AM(UTC)
RustyL

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Hi.

I am a new user of ViaCAD 2D3D 9. I should also point out that this is my first attempt at drawing in 3D, and exporting a file for use in a 3D printing process.

I recently created a new 3D drawing of a part I want to print on a 3D printer, operated by another team. The requirement is to export an STL file to be used by the team.

I have set-up the units in both the original 2D drawing, and the final 3D drawing as centimeters. Using the dimension tool in the 3D drawing, I am able to confirm the part is approx 2.2 units (cm) long. I exported the STL file using the default settings and the file was created successfully (no errors were reported).

When the printing team produced the part in the 3D printer, it was around 2.5 times the size I was expecting.

When I open the STL file in ViaCAD itself (which opens as 'Untitled.vc3'), and use the dimension tool, I confirmed that the STL file has specified the part as approx 5.6 units (cm) long.

The export process seems to have multiplied all the original dimensions by approx 2.5. Not sure if it is a coincidence that this is roughly the number of centimeters to the inch.

What have I missed here? Is there another config step I should have performed to ensure the export knows that the dimensions are already in centimeters and not inches?

I would really appreciate any assistance.

Regards, Rusty.
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rokoko  
#2 Posted : Wednesday, March 16, 2016 8:56:38 AM(UTC)
rokoko

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hi,

when using menu -> file -> import to import the stl into an empty drawing, you can choose units. maybe your printer team imported the file with inches
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RustyL  
#3 Posted : Wednesday, March 16, 2016 4:19:55 PM(UTC)
RustyL

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Thank you for your reply, rokoko.

In this case, I don't think the issue is on the import. The print team do not use ViaCAD - not sure what it is, but it is not the same package. That said, they could be doing the same thing, but I doubt it. Here's why...

The fact that the units are 2.5x on the exported file (before they even see the file) tells me the issue occurs in ViaCAD on the export. The export logic seems to assume the units are in inches and translates them to centimeters, regardless of what units are set in Preferences.

To test this theory out, this morning I changed the units in preferences to inches - the dimension changed from approx '2.2' (centimeters) to approx '.86' (I am rounding here) - and that is what I would have expected. I then exported the STL file again (exact same export defaults). I re-opened the STL file in ViaCAD and checked the dimensions: '.86' - CORRECT!

So it seems a work-around might be to change the units in preferences to inches prior to the export, and change them back to keep working in centimeters.

I am going to send the latest STL file off to the printer team now, and we'll see what comes out of the 3D printer - but so far it looks promising.

Standby....
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Tim Olson  
#4 Posted : Wednesday, March 16, 2016 10:59:02 PM(UTC)
Tim Olson

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Hi Rusty,

The STL file format does not support a unit descriptor. That means you will need to provide the file units along with the file or the scale could be off with whoever reads the file.

Tim
Tim Olson
IMSI Design/Encore
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RustyL  
#5 Posted : Sunday, March 20, 2016 5:26:29 PM(UTC)
RustyL

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Thank you for your reply, Tim.

I can report that the method outlined in my prior post worked perfectly. Not sure why, but changing the units to inches before the export produced the correct sized part in the STL file.

Regards.
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Claus  
#6 Posted : Monday, March 21, 2016 6:12:17 AM(UTC)
Claus

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I don't know what the issue is with your print team but I export stl in mm to my Dimension printer and import the file in mm to the print app. Works as expected.

Claus
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