Small improvement to Start/End GCode

Maybe that’s useful for others starting their 3D print experience with a TAZ:

With my first prints, I always had an anoing problem. During heatup, the nozzle oozes a little bit. When the print starts (usualy with a line around the part for priming), the nozzle is refilled. But this behavior leads to multiple problems, at least with PLA:
.) If you set the line around the object to a fixes value (1 line), that’s maybe not enough for small prints, ruining the first layer because it starts the print with a not fully primed nozzle.
.) If you set a fixed length of material to extrude for the skirt, that may result in more than one circle around the object. If now a blob happens during priming, which happens some times before a clear print line is laid down, it passes this blob which will lead to a messed up nozzle - another first layer ruined…
.) If none of the two above things happen, there can be a string of filament that is still attached to the nozzle due to unclean filament lay down at start that is dragged across the print area of your object. The first layer is than printed above this string…

I was tired of aborting prints just because something goes wrong before the first layer even started, so I start thinking about a solution with a start gcode. It’s not realy my invention, after I had my idea during searching for the right Gcodes for this I found other people doing similar things. Here it is, the final version! :smiley:

  1. After homing all axes, extrude some mm to get an “anchor”. Enough to fill the nozzle, less enough not the make the blob too big. 5mm is good for me.
  2. Move upward to exit this small blob, 99% of everything that was hanging on your nozzle is now away!
  3. Move a few mm away from the blob and start printing with a single loop for the skirt, just to be sure.

In GCode:

G28 ; home all axes
G21 ; set mm units
G90 ; set absolute coordinates
G92 E0 ; reset extrusion distance
G1 E5 F1800 ; extrude anchor
G1 Z5.0 F300 ; move platform down 5mm
G1 Y20 F3000 ; move away from the anchor

I also noticed that in the default end code there is a huge but slow retract. I removed it, it didn’t improve oozing at heat up and I don’t want to have molten PLA in the thermal barrier which can lead to a blocked hotend…
My version:

M400
M104 S0 ; turn off nozzle temperature
M140 S0 ; turn off bed temperature
G1 Y200
G28 X0 ; home X axis
M84 ; disable motors