Thursday, 28 January 2016

A bridge too far





Layer before roof: -

First bridging layer: -








Cura 15.04.3







Slic3r 1.2.9







Further up it gets a bit more strange.


CraftWare 1.13 beta


Simplify3D 3.0.2









  1. Just found out about this one myself, but does CraftWare produce any different results?

    1. I have added CraftWare, thanks for pointing it out. It too doesn't do bridges.

  2. In Cura you can disable combing to force retractions between infill lines. Cura does have code to decide on the direction of the top/bottom skin to get better bridging (per skin area), but I haven't tested bridging in quite some while.

    It's difficult for me to understand where you would like good bridging. Can you maybe attach a link to the model?

    1. Hi Tim,
      Thanks for the tip about retraction.

      The model is here:

      The ideal bridging is as Slic3r does but without the numerical errors. I.e. the first layer over the rounded end should always be exactly parallel to the unsupported edge so that no infill lines start, end or turn on that edge.

      On the sloping surface the unsupported infill should again always be parallel to the unsupported edge. The area of the bridge should extend right to the outside edges, not stop short.

      A slicer should never output paths that start, end or turn in mid air. Cura does that all over the place because it fills arbitrary areas on top of sparse infill. Skeinforge always fills to the edge and it always connects the ends of the infill at the edge. That means there is effectively a second skin for free and also gives something to support the infill ends of the layer above. Unsupported infill ends curl up and burn on the nozzle making unsightly brown marks on the prints.

  3. Also you can connect the end pieces of the infill lines by selecting zigzag as infill pattern in the new Cura, though I am convinced that the lines pattern is better.

  4. This is a great idea to have around if you want to test shroud designs. I design and test shrouds, but test them by printing small objects and overhangs and this is far from accuracy desired. If you are willing and able to test one of my models, I would appreciate it very much.

  5. We at Prusa3D are investing into the internal development of Slic3r, so I can explain both the issues with the Slic3r bridging algorithm.

    First the bridge orientation is calculated by testing various discrete orientations and picking the best. So this explains why the infill line is not aligned with the edge.

    Second, the infill on higher layers does not span the region because there is a "top" surface detected, which takes precedence. The "top" surface is any surface visible from the top and Slic3r by default extends the "top" surface region by 3mm to anchor it inside the object. This is not an optimal solution in many cases.

    By the way, Richard, thanks for the design of the cool meter, I have built one for our purposes.

  6. Thanks for the insights.

    BTW, my name is Chris, not Richard.

  7. Hello Chris!
    This project looks amazing! Did you have any interest in testing my part cooler design made and simulated in Solidworks?!topic/deltabot/ElN27Em78s4
    There are STL file and making history, if needed i can try adopt it to any configuration. I will be happy to see it tested in real life with your setup.