Cancel specific objects during print

[danilius 118]

No idea if anyone has suggested this already, but I would love to have some way to be able to top printing one or more objects in a multi-object print if they have failed somehow during the print.

[nallath 1,124]

This isn't possible due to how g-code works. The machine has no idea what one object or the other is.

[ahoeben 1,968]

Well, in theory comments could be placed in the gcode showing where different objects start, and the firmware could just skip gcode from the start-comment of such an object until it encounters a new start-comment for another object. But that would be a non-trivial change to the slicer and to the firmware.

[nallath 1,124]

And you would be depending on comments to ensure that it works, which is kinda nasty.

[danilius 118]

I was thinking along those lines. I fully appreciate that this is non-trivial, but it is nonetheless jolly useful.

This would of course could break Marlin in a big way, but perhaps not so drastically. As it is, the whole gcode thing is a bit long in the tooth for 3D printing, but assuming that we want to stick with it, one could add some very simple features into the firmware to handle this.

For example, bracketing each layer of each object with a start/end marker in comments as @ahoeben suggests. Standard firmware will simply ignore these comments, updated firmware will understand what they represent and could, upon receiving a custom gcode, simply skip to the next object on that layer.

Of course each object will need label, which could be set and/or autogenerated in Cura.

Maybe this is something for @Tinkergnome to play with?

[underwatercolor 0]

a) I agree this would be very useful!

b) Can Cura stop the print after completing a layer and send new gcode for the remaining layers of the print, (without some failed objects)? (I realize this would still be a lot of work / UI / etc, but seems less hacky than what was discussed above.)

c) If any of this works, maybe just being able to tell a print to stop/start at an arbitrary [Z] would put it in the user's hands.

Edited August 22, 2020 by underwatercolor
+idea