Possible bug with first layer height always showing 0.2mm

Phaedrux

Adding the layer height comment did not help.
Gcode generated by Cura is the same. Always shows 0.2 as the first layer height.

dc42

Do you have anything in your slicer start gcode that moves the head to Z0.2 ?

Phaedrux

Why yes I do. I purge a line of filament. Makes sense as I recently added that to the start code.

Is that expected behaviour?

dc42

The firmware determines the first layer height by looking for the first G1 Znn move where nn is a plausible layer height.

deckingman

I could be wrong but something at the back of my mind tells me that using G0 Znn instead of G1 Znn might be a cure? I believe G1 and G0 moves are treated the same as regards to movement but if the firmware looks for G1 Znn to determine layer height, would it ignore G0 Znn?

Phaedrux

I can give that a try.

Does it matter if the first g1 move is commented out or not? I could add ; G1 Z[first_layer_height] at the start.

dc42

Can't you use G1 [first_layer_height] at the start, followed by G1 Z0.2 ?

Phaedrux

@dc42:

Can't you use G1 [first_layer_height] at the start, followed by G1 Z0.2 ?

Now that you mention it, obviously I can. Thanks David.

Phaedrux

@dc42 So it doesn't seem to work as hoped.

; Purge some filament
;
G90 ; Absolute positioning
G1 Z[first_layer_height]
G1 X25 ; drop nozzle down to the bed
G91 ; Relative positioning
G92 E0 ; zero the extruded length
G1 X25 E5 F200 ; extrude 5mm while moving right
G1 E-0.5
G92 E0 ; zero the extruded length again
G90 ; absolute
G1 Z0.05
G91 ; relative
G1 Y10 F8000 ; wipe nozzle
G90 ; absolute
G1 Z[first_layer_height]
M400

The only Z height it seems to use for display in the DWC is the G1 Z0.05 now. It ignores the ones that use the slic3r variable place holders [first_layer_height].

Not a big deal.

dc42

What does the start of the generated gcode file look like?

Phaedrux

@dc42 it looks the same as what I posted above except [first_layer_height] has been replaced by the numerical value for the layer height. In this case 0.26

Full gcode here: https://www.dropbox.com/s/mleu5lljacvyq0k/Wooden_bowl.gcode.zip?dl=1

Phaedrux

Just an update.

I added a feedrate to the G1 command and now they show up in the DWC properly.

G1 Z[first_layer_height] F600