Faster Z-Lift and Retraction at end of print  

RE: Faster Z-Lift and Retraction at end of print

This line in the end gcode raises the nozzle:

{if layer_z < max_print_height}G1 Z{z_offset+min(layer_z+60, max_print_height)}{endif} ; Move print head up

You can add an Fxxx parameter for speed so it looks something like:

{if layer_z < max_print_height}G1 Z{z_offset+min(layer_z+60, max_print_height) F720}{endif} ; Move print head up

This uses a feedrate (speed) of 720mm/s which is 12mm/s. This corresponds to the maximum speed for the Z axis identified in the firmware. Not sure if that's really any faster.

I get a thin strand that's not really a problem, but I hadn't thought to try a faster Z speed. I'll give this a go soon myself.

RE: Faster Z-Lift and Retraction at end of print

@bobstro

Thanks, really appreciate it!  Is there a way to add a tad of retraction as well?

Edit:  It wasn't really a problem until I started printing with a specific PETG which likes it hot.  It seems to have a really fast Glass Transition phase, so it goes to solid to super melt pretty quickly.

RE: Faster Z-Lift and Retraction at end of print

Posted by: @cobalt-echo

[...] Thanks, really appreciate it!  Is there a way to add a tad of retraction as well?

Retraction is just an extruder move to pull the filament back at a set speed. The "magic" in the slicer is just that it inserts those commands wherever appropriate. You can see the retractions inserted by the slicer if you examine the generated gcode file in a text editor. All we're doing in the steps above is plugging in a final retraction. 

Edit:  It wasn't really a problem until I started printing with a specific PETG which likes it hot.  It seems to have a really fast Glass Transition phase, so it goes to solid to super melt pretty quickly.

That makes sense. PETG flows much more easily than PLA, IME, and more so at hotter temperatures.

One thing that is different with end gcode compared to normal retraction is that you are retracting before a vertical move, whereas retraction is normally done before a horizontal move (and a bit of vertical if you use z-lift/z-hop). Reading up on this, using faster XY speeds and acceleration can help reduce stringing by snapping the thread before it fully forms. I'm wondering if a bit of horizontal movement would help eliminate the final string. I did try manually inserting a small wiggle/wiping action at the end, but it didn't help much.

Just keep in mind that retraction doesn't create any suction. All it does is reduce pressure in the hotend. There's only so much you can do with it.