Search A Software For Bending An Stl Object 360/359 °

Discussion in 'Software and Applications' started by designgravity, Jun 19, 2017.

  1. designgravity
    designgravity Active Member
    Hello everybody,

    for printing at shapeways I'm looking for a simple and free program that bends flat STL objects (360 or about 359 °). A flat object to a ring (With a little distance between the ends.).

    With the free programs I use (e.g., 123D), this is only possible with Solid objects. Does anyone know of an online tool or program for such an operation?

    Thanks for tips!
     
  2. 1068084_deleted
    1068084_deleted Active Member
  3. designgravity
    designgravity Active Member
    The program is very complex. I hope I find a suitable tutorial for this operation.

    Thanks for the tip.
     
  4. Wedding3D
    Wedding3D Member
    Meshmixer, I think you can bend/ warp objects in that program and it's free.

    What kind of object do you want to band?
     
  5. designgravity
    designgravity Active Member
    Thanks for the program recommendations.

    To Blender:

    I've looked at some video tutorials. The bending as here in this video works.



    But unfortunately only as shown in the video, with the cube (Because it is a solid?).
    If I want to do it with my STL objects, it does not work. Apparently the problem is the cutting of the STL object (video min. 0:32). This does not seem to work with the STL object.


    To Meshmixer:

    Unfortunately, I can not install the latest version of the program. In the older version, which I have, I find no corresponding function. And unfortunately I could not find any video tutorials that have helped me.


    Here is a very simple example of what I would like to do (turn a flat STL object to 360 °):
    360grad.jpg
     
  6. MrNibbles
    MrNibbles Well-Known Member
    A general question, is there a good standards document for the stl format? I've thought about other model transform methods but I'm not clear on what makes an stl file do its thing. I would think such capabilities must exist somewhere? Certainly people must have played around with things like this before the arrival of more capable general editing programs.

    There should be a way to map or transform coordinates of a model in something like a spreadsheet or some other script editor by processing coordinate values using equations. But how easy that is depends on how easy it might be to screw up the stl file. The actual x,y,z coordinates should be easy to transform but isn't there some kind of vector associated with each triangular face that points inwards or outwards perpendicular to the face? Is this defined by an explicit set of numbers that define the vector direction or is it based on the listing order of the vertices of each triangle using some kind of right or left hand rule?

    Anyway for a flat sheet the math shouldn't be too hard to transform or map the sheet on a cylinder. You just need to know the circumference of the cylinder, and based on the length of the sheet whether its length when wrapped is preserved on the cylinder or scaled in some manner. Only the X and Y points would need to be transformed in a function. The Z data points would remain unchanged, unless you also want to scale the vertical Z dimension. But this is where the vector thing comes into play. Obviously the process of wrapping the sheet will require a change in direction of every triangular face vector in the mesh.

    Mapping a sheet with some thickness and surface artwork should not be much harder to process. The inside flat surface of the sheet say at Y=0 would map to the surface of the primary cylinder. Every other non-zero Y value would map to a cylinder having a slightly different radius. And again this amount could be scaled if desired.

    From a practical viewpoint you'd also need to start with a finely meshed sheet which means there would be lots of data points that require processing. Definitely not something to do by hand!
     
  7. designgravity
    designgravity Active Member
    It looks like I've found a way. It is certainly not optimal, but the first tests have worked.

    The principle is as in the video above. The cuts are simply made via Meshmixer / netfabb (by cutting and merging).

    This is how: Cut the STL object in Meshmixer into 1 mm wide strips (with "Make Slices"). Group all the strips and export them as one STL object. Repair the object in netfabb by automatic repair. This should connect all shells back to one single shell. Unfortunately, a lot of wrong-oriented triangles remain. Bend this new STL-file then with Blender (as shown in the video. Simply without the cut part.).

    This solution is no problem for small objects. For larger or more complex objects, however, this resulted for example in over 85'000 shells, which netfabb had to connect to a single shell. This needed some system resources. :)

    Perhaps you could simply refine the mesh structure of the objects rather than cut the object into slices. But maybe it just needs the nice straight slices / mesh structures.

    The twisted triangles still have to be corrected. But I think I'm on the right track ...
     
  8. mygadgetlife
    mygadgetlife Well-Known Member
    In Blender, take the original STL and apply a remesh modifier. With this you can push the polygon count very high, but also in a way that allows the Bend modifier to work the way you want. Good luck!


    Steven
     
  9. designgravity
    designgravity Active Member
    Thank you. I'll try that on occasion. Sounds good!
     
  10. designgravity
    designgravity Active Member
    Bending STL Files 360° (or any other degree values), is this possible with premium programs such as Rhino or formZ with a simple operation?

    I have a whole FDM optimized collection to bend, to optimize it for SLS printing.

    I wanted to look more closely for a premium program for new designs to find one that suits me. But I hadn't found the time yet. But perhaps this is a good criterion for the right choice of a software.
     
  11. JACANT
    JACANT Well-Known Member
  12. UniverseBecoming
    UniverseBecoming Well-Known Member
    Yeah, I second the recommendation for SpaceClaim.

    "I have a whole FDM optimized collection to bend, to optimize it for SLS printing." What do you mean by this? Can you explain further? I know about the two printing method but I can't figure out how you're optimising by bending into a cylinder.

    One way of doing it in Zbrush is to make a height map; in Zbrush, the command is called GrabDoc. From there you would apply the height map image to a cylinder comprised of millions of quadrilaterals and then make a displacement using the Apply DispMap command.

    The advantage would be there would be little to no distortion like you'd get via bending. The disadvantage is, it would be hard to setup since once you had your height map image you would need to make adjustments to the image in an image editor and or adjust the initialize on the Cylinder3D primitive so that the image would be mapped to the cylinder without distortion. Another disadvantage is there can be no undercuts. What I mean by undercut is, take a look at my bas-relief rhino in the turntable mode. See how that ear is filled in behind it?

    No-undercuts.gif
    I made this bas-relief via a height map image and displacement. I could have easily hand sculpted behind the ear to make it look good after doing the displacement, but at the time, I did it for a 3 axis CNC milling machine. To machine behind the ear, one would need at least a 4 axis machine, either that or a number of inconvienent repositions of the workpiece at intervals as the part was machined. I could put this same bas-relief on a cylinder and the distortions would be minimal. If interested let me know and I could walk you through it. You can get Zbrush as a 45-day trial if you don't already have it.