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Unique Slicing Needs, Looking for Guidance


GravyBagel

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Posted (edited) · Unique Slicing Needs, Looking for Guidance

I have a specific print that has a few finicky requirements. Essentially it is a 0.25" thick mesh made with lines infill [0,90], no walls, no top, no bottom. This part is unique in that other manufacturing methods are basically impossible because the hole sizes are so close the aspect ratios so high, so it provides something pretty unique.

 

There are a few requirements:

  • Need to clean up the edges so I have clean edges without post processing. Some methods:
    • Driving backward after reaching the end
    • Z retraction during movement backward
    • Z hopping
    • Filament retraction
    • Slight travel offset from end of line to account for diameter of filament blob
    • Combination of some or all of the above
  • Need to ensure that the grid formed by the infill is totally aligned to the part
    • I have not had good success trying to dial this in with the settings. Typically I'm off by a little bit and need to fight the slicer to get both the first and the last lines to actually slice. Need a way to do this repeatably and exactly.
  • Need to thin down all the edges. Basically, I need these to fit together and tile, so the wall thickness needs to be reduced around the perimeter and the spacing slightly reduced. I am ok with slight reduction in the opening, but it might still be clear. Proposed methods:
    • Alter G1 movements at the start and end of the shape to move in the desired direction and adjust filament extrusion
    • Add G92 to allow filament to pick up where it should have been in an unedited state

 

So I have a few options at this point. The shapes I need are very simple (squares). I am considering the following:

  • DIY slicer for specific use (Python + Shapely)
  • Plugin for Cura
  • Write post processor
  • Another more precise slicer with these options?

 

The first one is straight forward, but is probably a longer path. I wanted to ask folks in the community if the other two options are reasonable. The post-processor seems like a giant pain because the extrusion is absolute and not incremental. I could throw tons of G92's in there, but I think it would become a mess and might be more effort than writing a simple slicer from scratch.

 

If it helps, I'm working with an S5 Pro Bundle.

 

Thanks!

Edited by GravyBagel
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    Posted · Unique Slicing Needs, Looking for Guidance

    Some ideas as they came to me, so no particular order:

    • There's a fifth option, just write gcode from scratch, you'd just need to figure out the correct extrusion rates. The maths are probably somewhere online.
    • Instead of relying on making infill I would create a model of exactly what you want (piss easy in OpenSCAD, easy in FreeCAD, probably easy in several other programs), that way you can set the line width, spacing and alignment exactly as you want them, including thinning near the end.
    • If you're having problems with extrusion being absolute, M83 turns on relative extrusion while you're still in absolute positioning mode (and the M83 lasts until either a G90 or G91 is used) but you'd need use a post for Cura to convert the absolute extrusion values to relative, (but that wouldn't be hard).
    • It sounds like you have overhang at the ends of the lines for these to fit together? You'd need to use a dual extruder printer with a soluble material to print supports between each layer.
    • 9 hours ago, GravyBagel said:

      Need to clean up the edges so I have clean edges without post processing. Some methods:

      • Driving backward after reaching the end
      • Z retraction during movement backward
      • Z hopping
      • Filament retraction
      • Slight travel offset from end of line to account for diameter of filament blob
      • Combination of some or all of the above
      • That'll just lead to a thicker (width or height, depending on which way the filament goes) end because even with a retraction you'll still ooze a little bit.
      • Z retraction? Z goes up or down. Filament retracts.
      • Usually paired with a retraction, but still doesn't instantly get rid of all the filament at the end of the nozzle, plus you don't really need to Z hop to just to move over to the next line.

      • Still going to leave a blob on the end of the nozzle which has to go somewhere.

      • A blob isn't going to be that predictable. If I was doing something like that, I'd do a wicked fast travel move while retracting and hope the blob ends up somewhere that isn't the model.

    • For thinning down all the edges, making your model instead of just making infill is exactly what you need to do, that way you have control of how thin it gets, where it starts thinning, etc., rather than adjust the filament extrusion and hope it makes the wall thinner instead of shorter or something.

    • How dense infill are we talking, anyway? If it's not 100%, bridging at a scale that small should be possible, but it depends on filament, and density, and other stuff. Possibly including wind direction, even if you're inside. Basically bridging isn't 100% guaranteed but as I said, at that scale it should be alright.

    • 9 hours ago, GravyBagel said:
      • DIY slicer for specific use (Python + Shapely)
      • Plugin for Cura
      • Write post processor
      • Another more precise slicer with these options?
      • Really depends on how good you are at Python, but if anyone could just DIY a slicer they need existing ones wouldn't be so popular
      • Plugins are a major hassle, unless you're @ahoeben. Sounds like what you'd want could be done in posts, anyway.
      • If you're going to go that route, definitely split it up into multiple posts, one for each thing you want to do. Will make your life so much easier because Cura's post-processing script debugging is... somewhat lacking.
      • I know bringing up this name around here is heresy, but I think Prusa Slicer does give you a little more control, but probably nothing has everything you want. But if I was well educated on other slicers, I probably wouldn't spend so much time lurking the Cura forum.

     

     

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