Turbocad v Shapeways a possible mismatch

Discussion in 'CAD Corner' started by geoff_nicholls, 12 January 2018.

  1. geoff_nicholls

    geoff_nicholls Western Thunderer

    This is an appeal to fellow Turbocad users. I'd like to have Shapeways print a complicated driving wheel splasher, but I've had some expensive mismatches with 3D printing in the past with curved surfaces being printed a multifaceted polygons. It may be that I'm getting the same problem with Shapeways

    I thought I'd run a test, I used the 3D cylinder command, to create a cylinder:
    atest4 in turbocad.jpg
    but when I save this as an STL file then open it in AXON2 it looks like this:

    atest4 in axon2.jpg
    and after uploading in Shapeways:
    atest4 in shapeways.jpg

    I'm using Turbocad Professional 19.2 64-bit
    Am I panicking unnecessarily, or would it actually come out like an elongated threepenny bit?
     
  2. mickoo

    mickoo Western Thunderer

    Several of my parts appeared faceted in Shapeways but came back fine. Smoothing of 3D shapes takes a lot of CPU grunt, so many 3D viewing applications, especially web based ones will not use 3D smoothing. Thus you don't see exactly what you're getting which is not helpful.

    There's a free 3D object viewer that shoes what the object will look like and if it will print from a lot of commercial printers, can't recall it's name but will find it when I get home. Sadly though that also showed my items as faceted but your milege may be better.

    MD
     
  3. SimonT

    SimonT Western Thunderer

    Geoff,
    a lot of these packages have an control hidden in Options/Tools/some such alley way that allows the user to set the level of faceting on the model. Have a nose around the nether reaches. I use Rhino and Alibre so I cannot tell you where it might be in TurboCAD.

    Simon
     
  4. Dan Randall

    Dan Randall Western Thunderer

    Hi Geoff

    I had a cylindrical item 3D printed a few years ago that came out faceted, though in this instance it didn't matter.

    Looking at this phenomenon on a TurboCAD forum, it seems to be fairly commonplace, but a few people have offered suggestions that might help....

    Many facets instead of smooth.

    Good luck!


    Regards

    Dan
     
  5. Big Train James

    Big Train James Western Thunderer

    Autocad does have options to increase the smoothness of curves (Facetres, Viewres) but these are really just about managing memory usage and speed of regeneration when views are manipulated. They can be found under via display options. There may be a similar functionality in Turbocad, as they seem to share some features.

    Here are a couple of examples of how Shapeways will render the model for review, and the one printed example I have on hand of curved geometry printed in Frosted Extreme Detail.
    shapeways faceting.JPG shapeways faceting 2.JPG IMAG1385.jpg

    You can see some artifacts of faceting in the top edge of the plenum print, they are consistent all the way around. But in practice, the faceting is minimal, if even present at all. If I run something like a dental pick around the inside of the opening, it doesn't seem inclined to catch at any of the "corners" anymore than anywhere else. For scale, the opening is just over 1" in diameter.

    In my opinion, depending on scale and resolution requirements, there are better printing options available besides Shapeways. Those options most likely cost more than Shapeways, so a balance must be struck regarding value.

    Jim
     
  6. mickoo

    mickoo Western Thunderer

    Jim,

    That's interesting, I wonder if the STL generation is what you see on your screen, ramping up the smoothness might result in smoother objects in Shapeways? The STL code may hold data for material surface properties.

    The choice of Shapeways material seem to make no difference to the preview image.
     
    Last edited: 12 January 2018
  7. Brian McKenzie

    Brian McKenzie Western Thunderer

    Here's another TurboCAD thread that may offer some insight STL output

    While the onscreen display resolution can be cranked up within TurboCAD to smooth faceting, it appears that TC's conversion process into STL may only offer a limited coarser range of settings.

    I've never worked out at which point STL resolution matches Shapeways best output of 16 micron layer thickness. My software (Solidworks) offers control of STL res, so I move the adjustable resolution slider buttons out to the point where the file size approaches Shapeways maximum of 64mb ! While no doubt excessive, their automated processes soon crunch it down.

    I could output a high-res STL for you, from any file that SW can open for the purpose.

    -Brian McK.
     
  8. Big Train James

    Big Train James Western Thunderer

    It seems counter-intuitive to me for the stl generation to reflect what is onscreen, especially given that what is onscreen is acknowledged to be a representation and a compromise for the purposes of efficiency. I would think the stl would generate based on the real numbers behind the scenes.

    That being said, if the stl generation is based on extracting the surfaces from a solid model (watertight mesh sort of has that ring to it), then would it actually be comprised of lots of little triangles? And would smoothing, or using many more smaller triangles, lead to a better stl? I don't know. I know that in my shallow dive into Maya, there was a function to smooth or unsmooth objects, and the number of triangles comprising the object would change dramatically. The suitable number was again a balance between rough economy and luxurious smoothness, with the upper limit being a crash of the program.

    I've never taken an stl file into a dedicated viewer, so I can't say whether the faceting happens from the model to the stl, or from the stl to Shapeways.

    A quick search on google does indicate that an stl file is in fact an approximation in triangles, of the surfaces of a 3d object. But again, I'm not sure where degradation of the 3d model is taking effect.
     
  9. Big Train James

    Big Train James Western Thunderer

    Errr, mostly the same thing as Brian said while I was typing.

    Curious about the stl resolution. I wonder if autocad can do that. I'll have to check because I'm planning on printing some masters soon and I'd sure like to get the best results possible.
     
  10. mickoo

    mickoo Western Thunderer

    James,

    There is an stl export quality setting in Autocad, it's called FACETRES, type that and then type 10 (max resolution), the file size does bloat but boy oh boy the quality and smoothness of the object is staggering.

    Here's the stl output with the default export of 0.5....some seem to default to 0 but mine is 0.5

    Image10.png

    here's the same stl with it set to 10

    Image11.png

    The difference in file size is 339K to 2.5Mb but as you can see the quality is superb.

    The only downside is that the setting has to be changed each time you change your scene, or at the start when you open it, I think you can change it as a default in the *.dwt Template but I've no idea how to do that.

    Sorry for the hijack Geoff, but it for what it's worth, it does appear that you need to find a way to change the default stl export settings in your package.

    MD
     
    Last edited: 12 January 2018
  11. geoff_nicholls

    geoff_nicholls Western Thunderer

    this is all good stuff, thanks. These suggestions will help me frame my questions when I visit the Avanquest stand at the model engineering show at Alexandra Palace next weekend.
     
  12. Big Train James

    Big Train James Western Thunderer

    Default value for Viewres is 1000, default for Facetres is .5. If I go to options and change them (I like 20,000 and 10) they stay put from file to file and session to session.

    Since I tend to have my resolution values maxed out, maybe that is why I never really noticed a problem before.

    As to modifying template files, there's nothing to it. Just open the template file, make your changes, and save as a template file. Just like a drawing file.
     
  13. mickoo

    mickoo Western Thunderer

    James, so they do, I'd read that they didn't but maybe it's only an issue when making a new scene ?

    Didn't know about viewres, mine was 1000, changed to 10,000 and a little smoother, tried 20,000 and couldn't tell much difference and no slow down when scrolling or zooming so I'll stick to 10K.

    Facetres doesn't appear to impact the view in Autocad, only the exported stl file, the images above are from Shapeways when it views the exported stl file, proving that the value of facetres has an impact on the quality of smoothness of the object sent for printing.

    MD
     
    Big Train James likes this.
  14. Brian McKenzie

    Brian McKenzie Western Thunderer

    Already answered by Mickoo, but when I had a play got this:
    AutoCAD FACETRES affect on STL.jpg
     
    Big Train James and mickoo like this.
  15. Big Train James

    Big Train James Western Thunderer

    Lol, like many things in Autocad, there's a million variables but good luck knowing what any of them are except by accident. I didn't realize that's what Facetres did. Now I know.
     
  16. SimonT

    SimonT Western Thunderer

    In Alibre refining the faceting also effects the facets on the stl; yes I too have printed a hexagonal cylinder. In Rhino the two functions are separate and the stl export tool allows control over the mesh of triangles.
    • The simple control sets a tolerance for the maximum distance that the mesh of triangles can go from the solid model.
    • The complex control allows total control over all six attributes of the triangles.
    The above actions will affect the accurcy of your model and the file size. The Meshmixer Manual produced by the boys who designed Meshmixer gives graduate level information on how stls work. Unfotunately it is not available from those helpful folk at Autodesk but might still be available on the web. I have a copy somewhere on my hard drive if you cannot find it and are interested.

    Rhino also gives an option on the file formt of the stl - binary or ASCII, the later being the more compact file format if Shapeways (yuk) place an overall size limit. ASCII is about 5/8 the size of a binary file. Such controls would be worth finding in your drawing package.

    Simon
     
  17. Brian McKenzie

    Brian McKenzie Western Thunderer

    > I've never worked out at which point STL resolution matches Shapeways best output of 16 micron layer thickness.

    Apologies for the humongous image. Trying to answer my own question.

    The default 'coarse' setting in SolidWorks for creating an STL file looks more than adequate for anything that Shapeways can print at present. Happy to help Geoff boost the resolution of his wheel splasher STL file._____________Edit: Hook is 4.75mm overall in height.
    Hook STL.jpg
     
    Last edited: 14 January 2018
  18. Bill Bedford

    Bill Bedford Active Member

    Shapeways has a limit of 1,000,000 facets.

    Binary files are compressed, so should be smaller than an an ASCII.
     
  19. geoff_nicholls

    geoff_nicholls Western Thunderer

    thank you for all your responses and advice, I'll follow it up next week. Doing a drawing in CAD then posting it off and receiving a more or less complete finished object, is much more in my comfort zone than real modelmaking.
     
    DrIain likes this.
  20. Brian McKenzie

    Brian McKenzie Western Thunderer

    A portion of the STL file triangulation, from the 4.75mm high hook pictured previously, has been overlaid with red lines representing 3D printed layers of 16 micron thickness. This is about the finest resolution that Shapeways can offer.

    I'm not so sure now that the coarser STL file, at left, provides the optimum amount of data for the printing process at 16 micron level. Many of the triangles leap across several layers. However, in such a small part as this, any loss in form would not be discernible. Would it take on more importance for parts with larger radius curvature?

    Others have questioned Shapeways about STL resolution, but I haven't come across definitive answers - if indeed they are possible.

    STL resolution v 16 micron layers.jpg
     
    Dan Randall and simond like this.