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veedee

Stepfiles and G02/G03 arc gcodes

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Hello everyone,

I am working a lot with gcodes lately because of a very special dual extruder I am developing ;). Everytime when I manually want to adjust some gcodes for this dual, I experience those gigantic amounts of gcode.

Why is it that we use stl files instead of step files? Stepfiles use vectors instead of 3 dimensional 'pixels' so the stepfiles are smaller in size (there is no resolution), contain better information and are still adjustable in software like solidworks and inventor.

Another thing is that stepfiles use radii. In the world of cnc milling we use the gcodes G02 and G03 to indicate an arc with a specified radius. I think if we use this in 3d printing gcodes, the gcodes will get smaller in size and it is more clearly to make manual adjustments to it.

Perhaps this is a kick in the right direction, or maybe it's complete nonsense, but I wanted to say it anyway.

I also found out Cura doesn't support G02 and G03, obvious, because there are no arcs in an stl file. Maybe an idea for the next cura?

 

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I'm not saying step files aren't better - they probably are. But...

stl files also are scaleable (don't use pixels or voxels). If you have too many faces in your stl you can reduce using meshlab. Here's a tutorial:

http://www.shapeways.com/blog/archives/226-polygon-count-reduction-with-meshlab.html

G02,G03 would be great for adding to Marlin but... most of the curves in a design are either splines or are not necessarily the same radius in 3 dimensions. So they might not get a radii in step files either.

But if you are modeling a vertical cylinder it would be nice (horizontal cylinders won't get any advantage from G02,G03).

- George

 

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Simplicity. For example, the CuraEngine does a lot of polygon clipping/offseting. As far as I know polygon clipping with curves is not a fully solved issue like it is with straight lines. (for which I use Clipper btw: http://www.angusj.com/delphi/clipper.php )

I have, somewhere on my wish list, "Loading STEP files into Cura". But don't expect curves or arcs anytime soon in the GCode from me. But if I have curves before making the layer slices I can put a nice resolution to the arcs that is suited for your printer, instead of having a huge STL file.

 

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Daid - Does Cura downsample the STL files at all? I get the impression that it doesn't, such that when printing a high res 3D scan for instance, with a lot of geometry, I seem to get overly detailed sections with very short line segments that cause stuttering - presumably due to buffer underruns, even from SD card.

I know that thin/small sections get filtered out during slicing, but that doesn't seem to be the case for detailed parts of otherwise large islands.

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Details get reduced, but only to the point where you do not change the print result, and some very small things can still impact the results. I know it can generate GCode which causes slowdown even on SD printing. But else I had reduction of visual details.

 

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Both kisslicer and Slic3r allow you to set a sampling resolution (which is the only way I can get Slic3r to even process some of my STLs) and I think it would be good if Cura had that option under the hood somewhere. I suspect that the uneven extrusion due to slowdowns and stutters does more harm than any minimal benefit from capturing marginal extra detail.

I know I can decimate the mesh externally, but I prefer to keep one detailed mesh that I can print at a range of sizes, rather than having lots of files at different scales.

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