Does Shapeways Alter User Models Before Printing Or Is It Wysiwyg?

Discussion in 'Design and Modeling' started by MapBliss, Dec 11, 2016.

  1. MapBliss
    MapBliss Active Member
    Is Shapeways supposed to be more or less WYSIWYG? Or does the software that runs the printers smooth, or otherwise alter models after they are uploaded?

    I uploaded a small terrain model created as a TIN (triangulated irregular network). It basically models the land surface as triangular facets instead of smooth ground. After upload to Shapeways the model passed all validations and the online preview clearly showed the facets I wanted to print. But now that I have the finished print, I don't see any sign of the facets. It looks very much like the software (or a tech) smoothed or interpolated my model before printing.

    This is my second print with Shapeways, but first faceted terrain model. I'd like to do more, but not if I can't count on the preview being a fair representation of what I'll get when it prints.

    Screen Shot 2016-12-10 at 8.21.54 PM.png

    thumbnail_IMG_3163.jpg
     
  2. MrNibbles
    MrNibbles Well-Known Member
    If you ordered SF orange the part is slightly polished before the dye bath so that would remove some detail. But even with unpolished SF you may not see the facets or sharp edges so easily depending on how small they are relative to the print layer thicknesses.

    As far as how the files might be processed for different materials and printers that's a good question, but most likely there's also a large variability in what comes out of various machines over time even if everything is done the exact same way each time.
     
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  3. stonysmith
    stonysmith Well-Known Member Moderator
    No, the geometry you upload is not smoothed before it's printed. As @MrNibbles mentioned, any of the Colored Strong Flexible materials are run thru a polisher first so that the dye will adhere better.

    Usually, it's the other way around. Some prints end up with "stepping lines" where the facets are are terraced, not smoothed.
     
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  4. MapBliss
    MapBliss Active Member
    Interesting. I thought the polishing would actually help enhance the detail of the facets!

    For reference, this model is about 15cm x 6.3cm and 1.5cm thick. I'm planning to make a silicone mold of the print to then cast cement or resin models from.

    So if my goal is to retain as much of the faceted surface as possible, but also get as smooth a surface as possible for making the mold, what material should I be printing in?

    Any other tips for helping ensure I get the look I want? I have another model to print (Tahoe) but I can't afford to guess at what it will come out like.

    Screen Shot 2016-12-10 at 10.40.58 PM.png
     
  5. glehn
    glehn Well-Known Member
    I think you should try FUD or the new Black Acrylate. They should give you the finest resolution and preserve the details.

    Regards,
    Luis
     
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  6. MapBliss
    MapBliss Active Member
    Thanks, FUD and BA are both too expensive at this model size for me to experiment with ($180 and $150 respectively). Looking at small detailed model examples (incl from smallscaleshop) it looks to me like fine details are not really an issue in this material so I think something else must be going on. I would expect even with the polishing to see remnants of my faceted surface, even if over rounded, but I don't.

    While cleaning up another TIN model in Meshmixer I tested the Make Solid function which had the effect of re meshing my entire model from its irregular facets into a mesh of smaller regular triangles, which made the virtual model look very much like the print, no facets. I'm still not convinced something like that didn't happen to my model between order and print.
     
  7. MapBliss
    MapBliss Active Member
    Here's what I'm talking about. First image is the model in Meshmixer as submitted to Shapways, larger facets obvious in model. The second image is after running Make Solid and is more like what I got as a print:

    Screen Shot 2016-12-11 at 8.11.53 AM.png
    Screen Shot 2016-12-11 at 8.12.21 AM.png
     
  8. paulopereira
    paulopereira Active Member
    Hi,
    To make the prints cheaper you may consider making them hollow.
    In some cases you can reduce the price by 50-70%.

    The SF is printed from a polyamide (nylon) powder, what happens is the edge sharpness is dependent on the powder grain and laser diameter. That loss in detail is really not surprising.

    Hope I helped
     
  9. NoahLI
    NoahLI Well-Known Member
    if you ran SW's autofix on an upload, the model is changed. otherwise it's as you uploaded, even the same format as you uploaded. You can check this using the download button after you upload a file. you will get a zip file containing the original file you uploaded. If you used autofix, you get an X3D file.

    however it's never exactly WYSIYG, as the printer resolution is not nearly as high as your display. And you are printing smaller than the displayed size. Same effect as rescaling down a bitmap image: pixels get resampled and details get lost. The orange print is what I'd expect from your first screencap, since colored nylon prints are polished, the process will reduce small details and make everything look rounded. There's no possible way a polishing process will enhance details since polishing removes material starting at the highest points, exactly the opposite of enhancing details.

    Print orientation also plays a role. The test print was printed with large flat side down, you can try setting orientation so it's side ways with one of the edges down. It can give better results on gradual slopes and curves like much of your terrain.

    last factor is material, SLS has minimum feature size of 0.2mm, although for practical purposes it's closer to 0.5~0.7mm. Anything raised details than 0.5mm may not consistently print, and would certainly be lost during polishing.
     
  10. MrNibbles
    MrNibbles Well-Known Member
    I would recommend you start small. Cut out a smaller piece of the map, perhaps one with the most detail, and have it printed in a few materials so you can compare results. This is a good way to waste less money.

    A lot of things can happen in the print process. The first thing that is done is to convert the file into slices. Different printers for different materials will have different layer thicknesses. The slice file calculates the intersection of each layer with the surface of each model facet it comes in contact with. If a facet is large enough multiple intersections will be calculated both within a slice layer and for multiple slice layers. If the facet is too small the slice layer may ignore that facet. And to compund the problem vertical step resolution might be different than horizontal laser dot resolution. This is a fundamental filtering or aliasing process that can slightly alter your model but it's not the same thing as smoothing an entire 3D file like Meshmixer might do.

    Then as @paulopereira pointed out the printer settings and source material can affect how the lasers solidify material. This is another filtering process that can "smear" fine detail. And finally cleaning and polishing the prints after they come out of the machine may have an additional effect.

    Meshmixer can be a tricky beast when it comes to fine detail. Running make solid may have emulated the printing process to some extent but the full 3D file is not altered in that way at Shapeways. Just the plain act of remeshing a model in Meshmixer can mess up your model detail unless you use the last option that simply subdivides existing facets. I have no idea of what Meshmixer can do well since I'm somewhat memory limited at the moment. But it's my experience that some functions in the program benefit from a very fine remeshing beforehand.

    You should be able to hollow out your slab using Meshmixer with no ill effects to reduce cost of the print. Maybe also remove the bottom flat section and add a thin rim around the bottom for support while molding (like this), assuming you are trying to create a model master. That would negate the need for cleaning out the hollow cavity which could be a pain in some materials.
     
    Last edited: Dec 11, 2016
  11. MapBliss
    MapBliss Active Member
    I didn't run autofix, just submitted as uploaded. In my mind I imagined that "polishing" was a method for removing print fuzz or other artifacts of the process, revealing the model underneath. That's more a subtractive thing though I think. When I buff out CNC wood models I get more detail, not less.

    Just starting to experiment with hollowing in Meshmixer. I think I can see how to do that and drop the bottom plate as well, will give that a try, thanks.

    I should also get an accurate measure of some of the facet sizes to see how they compare to the feature minimum sizer specs.

    Thanks all.

    David
     
  12. MrNibbles
    MrNibbles Well-Known Member
    You can do a boolean subtract with a box enclosing the bottom plate to remove it. But you might need to remesh the box to a finer mesh first to get a clean cut. Not an expert in MM so there's probably more than one way to do this.

    Another tip. If you add something to your MM file, like a mounting flange for example, you can overlap and "combine" the pieces so they look like one solid part without having to "make solid" afterwards to get a model with a continuous mesh. As you probably noticed the "make solid" remeshes things. When you upload separate overlapping model pieces to Shapeways their software will merge them and I don't think it affects the mesh away from the intersection areas. Of course you can download the "merged" file to verify the result of this.
     
  13. NoahLI
    NoahLI Well-Known Member
    polishing process with plastic prints is more like sanding in woodworking, with medium grit paper. Buffing wood or metal is more like "finishing", you are still removing material, though in much more minute amounts, the effect is increasing visual contrast between rougher and buffed areas of the surface, accentuating detail. If you buff long enough, details will still get destroyed.
     
  14. MapBliss
    MapBliss Active Member
    I finally received my test prints for the faceted Mt Hood model in both polished and unpolished White Strong and Flexible. I've examined the models and I'm now convinced that something is not right about my 1551045 order. Both of the test pieces show the same shapes and details as the Shapeways rendering. In both test models the geometric surfaces and edges of the facets are clearly visible, despite the polishing. The only real difference between polished and un polished is the texture of the material. Compare that to my previous order where the finished model is completely smoothed compared to its faceted rendering on Shapeways. From my test I can't see how the polishing could remove that much detail or alter the shape of the models surface to that degree. It looks very much to me like earlier model was re meshed prior to being printed which has the effect of smoothing those facets out.
     
  15. NoahLI
    NoahLI Well-Known Member
    Polishing removes around 0.2~0.3mm of material, enough to completely smooth out print lines on convex areas. concave areas receive less polishing, pellets are 2mm diameter by 4mm length, with slanted ends that taper to maybe 0.5mm. any concave areas smaller than that will receive very little abrasion if any at all.

    Even taking polishing in to account, the orange print from 1st post is much closer to the faceted preview than the blobby smoothed version you linked few posts later.

    smallest printable detail is around 0.1mm at best, any facets smaller than that will be lost, effectively smoothed out, during print before any kind of polishing happens.
     
  16. MapBliss
    MapBliss Active Member
    Given the test results I think its much more likely that the stl model was either too small to render facets or the file was modified somehow. Given the very delicate and small details I can see in may of the prints in the Shapeways store I'm not sure how the model facets would have been too small to print, but will see if I can get some measurements to compare. Will also be re printing a test section of the original model in a few other materials to compare results.
     
  17. stannum
    stannum Well-Known Member
    Did the problematic model require autofixes by SW?
     
  18. polished prints can vary, i had one that really didn't hold up well, was uneven just didn't come out right and i would say was faulty via the printing process. with experience maybe you can recognise when this has happened. it hasn't happened to me too often and mostly prints are consistent.

    just a word on note, my opionion for what is worth, on what you are trying to achieave. usually i put everything through polish but i am trying attain smooth results, if you are doing terrain i would say the unpolished would work best as it means many of your sharp peaks will be retained and not smothed down. with such a rough model such as your mountains etc i would think unpolished would be best, polished can take away some of the terracing effect of 3d printing but your model may not ever take away all anyway meaning you lose sharps edges and still have terraces.

    also note when you view your model in the product/shop section on your account, making render images of each material will give you a simulated image of how your model will come out in that material. so you should get an idea how each material will respond, might be usful.
     
  19. MrNibbles
    MrNibbles Well-Known Member
    A year or two ago they had some issues with SF plastics because apparently the humidity dropped in the factory or something like that causing the prints to be less dense and a little chalky. I think it also resulted in lower resolution of print details. Maybe that print is suffering from some winter 2016 version of that? It's my guess things are much likely to be goobered up because of a printing issue than remeshing.

    On the other hand I'm pretty sure that the only time the models are affected by "remeshing" is when CustomMaker is used, and in that case they run the model through Shape JS and do some voxelization that may be different for different materials. Did you by any chance have some text applied to your model using CustomMaker?
     
  20. MapBliss
    MapBliss Active Member
    Not that I implemented, but there is a part of the actual print that has extra material on what was a thin ridge, looks a lot like the result of the fixes SW would put on other models when I've tried that function. It's another reason I feel like the file I submitted was not run "as is".