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Discrepancy dimensions CAD file / CURA


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Posted · Discrepancy dimensions CAD file / CURA

Today I noticed something strange...

I have a small object to print. Basically nothing more than a 15mm high ring with an outer diameter of 28mm.

Designed in FreeCAD, exported as STL and loaded into CURA.

Now when I look at the dimensions in CURA, there is a small but noticeable deviation between X and Y, which moves as the ring rotates.

You would think that 28mm is also 28mm in CURA; that's not the case...

Why is that?!?

 

img-2024-07-04-09-56-19.png

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    Posted · Discrepancy dimensions CAD file / CURA

    What does the size indicator in the bottom left say? That should be the size of the imported file (although it might just round it up to 28 anyway).

    image.thumb.png.cf9f823f98fb0c8d36afe25942e22c61.png

     

    It's also possible FreeCAD didn't export the STL as perfectly as expected (you have to know exactly where to look in the settings to control the output resolution of STLs, especially when it comes to angle increments) but the size is well within a reasonable margin of error.

     

    And... I can understand why you're curious, but someone show me a printer capable of a 0.0087mm resolution and then I'll say this is something worth worrying about 🙂 

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    Posted · Discrepancy dimensions CAD file / CURA

    You are of course right about the minimal discrepancy that no printer can currently display.

    And you are also right that I just want to know. It has to come from somewhere; that kind of thing always bothers me...

     

    The measurement is correctly given in the bottom left corner. So there is also a discrepancy in CURA itself...

    I'll take a look at what I can set in FC regarding the resolution of export files; I'm still a beginner there also...

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    Posted · Discrepancy dimensions CAD file / CURA
    31 minutes ago, CBX_Micha said:

    The measurement is correctly given in the bottom left corner. So there is also a discrepancy in CURA itself...

    Nah, Cura's just rounding it on the bottom left corner. It'll never go beyond one decimal place:

    image.thumb.png.84c9f1164a6cd788fa49c343c0dc04c2.png

    (and your discrepancy is obviously far less than that)

     

    35 minutes ago, CBX_Micha said:

    I'll take a look at what I can set in FC regarding the resolution of export files; I'm still a beginner there also...

    It's totally not confusing. Just like the rest of FreeCAD.

    If your object is a mesh in FreeCAD (green icon in the object tree image.png.01843ce349735be63ae1bb0fc29cb504.png) then you go to

    Edit > Preferences > Import/Export (on the left) > Mesh Formats (at the top) > Export > Maximum mesh deviation

    If your object is a body in FreeCAD (blue icon in the object tree image.png.e2ba04c66f97b4b8fcc83fed800718db.png)... or pretty much anything other than a mesh:

    1. Go to the Part Design workbench
    2. Go to Edit > Preferences > Part/Part Design (on the left) > Shape View (at the top) > Maximum deviation depending on the model bounding box and Maximum angular deflection
    3. I'm not kidding, those settings don't show up unless you're in the part or part design workbench. Totally not confusing.

    If your object isn't a mesh, it might be worth converting it to one and exporting that.

    1. Go to the Mesh workbench
    2. Select your object in the object tree image.png.3f54886662031a02fcf72052539be10d.png
    3. Use "Create mesh from shape" on the toolbar at the top image.png.495ab3637fefe5e76db8eb20f63bc912.png
      The panel on the left will then go to the settings for creating the mesh where you can set things like the maximum deviation. Set those and click "OK" at the top.
    4. Use "Export Mesh" on the toolbar (should be next to create mesh) image.png.cae463171066d4fb3d8e85668e7264a0.png
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    Posted · Discrepancy dimensions CAD file / CURA

    Thank you very much for the good advice.


    I have now set

    ... > Shape View > Maximum deviation = 0.1% 

    and

    
    ... > Shape View > Maximum angular deflection = 18°


    I also made a mesh out of the part and exported it with the defaults specified by FC.
    The direct export of the Part > STL did not change the values in CURA, the export of the Mesh > STL is worse than the direct Part export...

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    Posted (edited) · Discrepancy dimensions CAD file / CURA

    OK, something is totally wrong here!

    I have now exported four cylinders from FC, each with a 0.2mm difference in diameter.

    When I import these files into CURA, they are all the same!

    The following is specified in CURA: (Dia FC -> left bottom corner -> scale)

    • 27.0mm -> 27.6x27.6 -> X=27.5885, Y=27.5943
    • 27.2mm -> 27.6x27.6 -> X=27.5885, Y=27.5943
    • 27.4mm -> 27.6x27.6 -> X=27.5885, Y=27.5943
    • 27.4mm -> 27.6x27.6 -> X=27.5885, Y=27.5943

    STL files and FC attached in the ZIP

    Dia is defined in FC

    Quote

    Ringkörper/Zylinder/Sketch001

    - outer dia

    E-Technik.zip

    Edited by CBX_Micha
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    Posted (edited) · Discrepancy dimensions CAD file / CURA

    I opened your FreeCAD file and the two pads were invalid and wouldn't recompute - so it'll just export the last model it could compute.

     

    Hadn't seen the error in FreeCAD before so had to look it up and the solution is here.

    Here's a couple I exported after fixing that (and then changing the sketch to increase the diameter).

    image.thumb.png.7bcfa1ad55b08d5193d59f948c0d6784.pngimage.thumb.png.44c3c11661b942bebd3a26908c4466fc.png

     

    Edit: Also it appears I'm exporting in much more detail than you:

    Yours: image.png.f97d134b2c7709a711993f3e94321cbc.png

    Mine:  image.png.3faf3b95a1748e7a5f891a992a585f44.png

    Mine's too much actually - I've had to use MeshLab to decimate some of them to get them to a reasonable size 😄 

    Edit #2: Here's my settings:

    image.thumb.png.3054a1a2ce136ce5c2f3e3b3ce008054.png

    Edited by Slashee_the_Cow
    added bit about detail
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    Posted (edited) · Discrepancy dimensions CAD file / CURA

    Crazy... Many thx for your time to spend in this.
    I have read the solution but I'm understand ... nothing 🥴 
    I always thought that at least an error message or the usual red exclamation mark would appear on the pad if something was wrong...
    Originally I had also tried to generate this cylinder in one piece as a turned part, but FC keeps running into an error that I couldn't fix...

     

    EDIT say:
    Got it.. Reading and trial and error helped 😉
    If I double-click each pad after changing any in a Sketch, everything is fine again.
    I would have assumed that this error had been fixed in the current dev a long time ago. Because I have "automatic recalculation" activated in the settings. Unfortunately, it doesn't help to mark all parts and use all marked recalculations; it doesn't change anything...

    Edited by CBX_Micha
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    • Solution
    Posted · Discrepancy dimensions CAD file / CURA
    8 hours ago, CBX_Micha said:

    EDIT say:
    Got it.. Reading and trial and error helped 😉
    If I double-click each pad after changing any in a Sketch, everything is fine again.

    Those weren't the instructions, but if that works for you... go for it. To summarise the instructions to fix it so that you hopefully don't have to manually intervene each time:

    1. Select your pad in the tree menu:
      image.png.15659de9ae1e190741dfca67d96267ee.png
    2. In the settings below that, go to the bottom and click Sketch Based > Profile:image.thumb.png.e6e7eb6657c1d1d59548420c18bdd075.png
    3. Click the ... button that came up there and in the popup click Clear and then OK:
      image.thumb.png.08b840caa466da01f99332107e466c3e.png
    4. Click the ... button again, select your sketch from the list and click OK:
      image.thumb.png.3a450c4e94c356fc2a20ce1b65c46e99.png
    5. Repeat for each pad.

    No I have no idea why the hell this works. It's FreeCAD. Understanding why would probably make your brain explode.

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    Posted · Discrepancy dimensions CAD file / CURA

    Ahhh, thank you. I could understand that now. But it doesn't really work in the 38001dev.
    Only the pad belonging to the sketch is corrected, but the rest remains faulty. So it has exactly the same effect as the double-click on a pad after making changes to the sketch.
    Ultimately, neither is a problem if the component only has a few pads; with complex components, it becomes a click orgy... 😵

     

    5 hours ago, Slashee_the_Cow said:

    It's FreeCAD. Understanding why would probably make your brain explode.

     

    So true, so true 🤪 There are some bugs that have been creeping through all versions for months and years and make life difficult for beginners and, I believe, also for pros. Or bugs that are simply brushed aside in GIT as "unplanned"; nobody understands...
    But what do I know? I'm not a coder and have no idea about it. There must be a reason for that...

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    Posted · Discrepancy dimensions CAD file / CURA

    BTW OT: Why can't CURA most don't read 3MF (read but is empty)? License problem?

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    Posted · Discrepancy dimensions CAD file / CURA
    32 minutes ago, CBX_Micha said:

    BTW OT: Why can't CURA most don't read 3MF (read but is empty)? License problem?

    I don't have problems reading most 3MF files. Sometimes it can get the position of objects wrong but they load fine.

     

    If you can provide an example or two of files which don't load properly we can have a look at them and try and figure out what might be causing issues.

    two objects.3mf

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    Posted · Discrepancy dimensions CAD file / CURA

    I can open your file with the two parts. They stay outside in front of the left corner... That's works well so far...
    I have taken a look and find some I get the error that there are no parts in the file; attached as ZIP originally downloaded from MakerWorls

     

    CUBE+CLOCK+-+fot+KIT+011_IKEA.zip

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    Posted · Discrepancy dimensions CAD file / CURA
    34 minutes ago, CBX_Micha said:

    I can open your file with the two parts. They stay outside in front of the left corner... That's works well so far...
    I have taken a look and find some I get the error that there are no parts in the file; attached as ZIP originally downloaded from MakerWorls

    Cura isn't the only program which can't open those - I couldn't open them in several others.

     

    I'm no expert in 3mf files but I can't help but notice that for the ones you provided the models are stored in multiple files in separate folders (yeah 3MF files are just zip files):

    image.thumb.png.e8944ebc41b7356183a840258839c1b6.png

    image.thumb.png.27b06f8a6079c4b86013e2462d154d09.png

     

    But for the one I made, both objects are stored in the same file:

    image.thumb.png.30a7ebae716975b084146af1dbdefabb.png

    I checked several other 3MF files with multiple models that load successfully and they're the same.

     

    What I'm guessing is that whatever program the ones you provided exported in its own custom kind of 3MF.

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    Posted · Discrepancy dimensions CAD file / CURA

    Seems so. I often crash into this (for me useless) files at MakerBase. No idea why but I think at the moment every coder have it's own idea far from every norm...
    Thanks again for your research on this. That explains a lot...

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