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STL export-- arbitrary coordinate system?

michael_bush
michael_bush Member Posts: 1 PRO
edited November 2016 in Community Support
Hi-
I've got a model where the parts are all where I want them to be, but when I create an STL export, the origin is moved to some apparently arbitrary place inside the body.  
This is problematic because I'm trying to produce models that can then be manipulated (in another software package) with a coordinate transformation.
How do I force the STL export to use the coordinate system that I've designated in the model?
thanks,
Michael

Answers

  • rex_hanson
    rex_hanson Member Posts: 41 ✭✭
    I have the same question. Looks like there isn't an answer since this was first posted back in 2016.
  • mthiesmeyer
    mthiesmeyer Onshape Employees Posts: 115 image
    Hi @rex_hanson,

    STL files are simply a list of x, y, z points defining triangles that, when rendered, look like the shapes that you were modeling. If you create some geometry offset from the origin by a significant amount:



    then export that geometry as stl and re-import to Onshape (ensuring that import units are the same as export units), you will notice that the geometry has not changed position:



    What software are you importing your STL file into? It is possible that they designate a different axis as y (perhaps y pointed up?) or that they are trying to be helpful by centering your geometry on the origin after import.

    Best,

    Mike
  • rex_hanson
    rex_hanson Member Posts: 41 ✭✭
    I'm importing my stl file into Makerbot for 3D printing. The problem is I started with an imported CAD geometry that has an angled surface that I'd like to use as my reference when exporting my new geometry. As it is, my exported geometry comes in at an angle due to the initial reference coordinate system used to generate the stl file. It is simple enough to rotate my model in Makerbot if I want to do a straight print. But if I want to scale the model in one direction then it is impossible to do since the part is tilted in space relative to the default coordinate system of the part. If I could select a reference frame to use when creating the stl file then it would be easy to scale the stl file in the standard XYZ directions. The model I'm working on with this issue is:
    https://cad.onshape.com/documents/9e862dc61083856716a3b568/w/9518ac2e5bf0597d55ad12a6/e/05def64b3ee0bd111485c700
  • owen_sparks
    owen_sparks Member, Developers Posts: 2,660 PRO
    edited January 2019
    Why not scale the model in CAD? (Onshape has linear and non linear scaling then the transform function.)
    Cheers, Owen S.
    Business Systems and Configuration Controller
    HWM-Water Ltd
  • MBartlett21
    MBartlett21 Member, OS Professional, Developers Posts: 2,064 ✭✭✭✭✭
    You can use transform by mate connectors or rotate to transform it so it points the right way.
    You can then scale your part
    mb - draftsman - also FS author: View FeatureScripts
    IR for AS/NZS 1100
  • rex_hanson
    rex_hanson Member Posts: 41 ✭✭
    I had the same problem with exporting files for 3D printing. Here is how you do it:
    1) Add a mate connector to each part you want to export. Orient the Z axis so it will point up when you bring it into the Makerbot software.
    2) Create a new assembly and add a mate connector. Locate it at the origin of the assembly. By default the Z axis will be point upwards. Not sure about the orientation of the X & Y axis.
    3) Assemble your part into the assembly and then use a fasten mate to locate the part relative to the mate connector in the assembly.
    4) Export your file and all of the values are now relative to the mate connector in the part.
    5) Repeat this for each part, making sure you only have one part at a time in the assembly as you will be exporting the assembly and not the part.

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