Clarification about Z axis step down

hello :smiley:
I am a new user. I use kiri:moto basically for the CAM feature since some weeks.
Thanks for the great piece of software you shared to the world!

I have a question about the Z axis behaviour during the milling.
I am milling 10 mm wood.

I set for example only the outline phase with a 4 mm of step down.
The Z thru is set to 2 mm.
The Zero is on “top”.

Basically I was expecting to have 3 passes:
- the first at -4 mm
- the second at -8 mm
- the third at -12 mm (this already overcome the 10mm, i have a wasteboard, so it is ok :stuck_out_tongue: )

Otherwise what the GCODE says is different:

4 passes:
    - G1 Z-3.3400 F100
    - G1 Z-6.6600 F100
    - G1 Z-9.9900 F100
    - G1 Z-11.9900 F100

Am i doing something wrong or is this an expected behaviour?

Here the full gcode of a cube (100x100x10)mm:

; Generated by Kiri:Moto 2.4.D8
; Mon Nov 30 2020 18:50:50 GMT+0100 (Central European Standard Time)
; Bed left:0 right:600 top:1200 bottom:0
; Target: LOWRIDER
; --- process ---
; processName = default
; camRoughTool = 1001
; camRoughSpindle = 1000
; camRoughDown = 4
; camRoughOver = 0.5
; camRoughSpeed = 250
; camRoughPlunge = 100
; camRoughStock = 0
; camRoughVoid = false
; camRoughFlat = false
; camRoughTop = false
; camRoughIn = false
; camRoughOn = false
; camOutlineTool = 1606756957954
; camOutlineSpindle = 1000
; camOutlineDown = 4
; camOutlineSpeed = 250
; camOutlinePlunge = 100
; camOutlineWide = false
; camOutlineOut = false
; camOutlineIn = false
; camOutlineOn = true
; camContourTool = 1000
; camContourSpindle = 1000
; camContourOver = 0.5
; camContourSpeed = 1000
; camContourAngle = 85
; camContourCurves = false
; camContourIn = false
; camContourXOn = false
; camContourYOn = false
; camTraceTool = 1000
; camTraceSpeed = 250
; camTraceOn = false
; camDrillTool = 1000
; camDrillSpindle = 1000
; camDrillDownSpeed = 250
; camDrillDown = 5
; camDrillDwell = 250
; camDrillLift = 2
; camDrillingOn = false
; camDrillReg = none
; camTabsWidth = 5
; camTabsHeight = 5
; camTabsDepth = 5
; camTabsOn = false
; camDepthFirst = true
; camEaseDown = false
; camOriginTop = true
; camZTopOffset = 0
; camZBottom = 0
; camZClearance = 3
; camZThru = 2
; camFastFeed = 1000
; camFastFeedZ = 300
; camTolerance = 0.15
; camStockX = 10
; camStockY = 10
; camStockZ = 0
; camStockOffset = true
; camStockOn = true
; camConventional = true
; outputOriginCenter = false
; outputInvertX = false
; outputInvertY = false
; --- tools ---
; tool=1 flute=0.25 len=2 metric=false
; tool=4 flute=3.175 len=20 metric=true
G21 ; set units to MM (required)
G90 ; absolute position mode (required)G0 F600 ; default rapid move speed
G1 F250 ; default cutting speed
M92 X160.77 ; stepmm
M92 Y160.77 ; stepmm
G92 X0 Y0 Z0 ; set home
; starting outline pass
M6 T4 ; change tool to '3175'
G0 Z3.0 F300
G0 X106.5875 Y106.5875 F1000
G1 Z-3.3400 F100
G1 X3.4125 F250
G1 Y3.4125
G1 X106.5875
G1 Y106.5875
G1 Z-6.6600 F100
G1 X3.4125 F250
G1 Y3.4125
G1 X106.5875
G1 Y106.5875
G1 Z-9.9900 F100
G1 X3.4125 F250
G1 Y3.4125
G1 X106.5875
G1 Y106.5875
G1 Z-11.9900 F100
G1 X3.4125 F250
G1 Y3.4125
G1 X106.5875
G1 Y106.5875
M6 T1 ; change tool to 'end 1/4'
G0 Z3.0 F300
; ending outline pass after 7 seconds
M30 ; program end
G1 Z10 
G0 X0 F1000
G0 Y0 F1000

Thanks, Umberto :slight_smile:

Hi Umberto and welcome! Thanks for your code contribution (gcode preview on export). I think the others will appreciate it.

If you set z thru it will generate an extra step down. This is because the z thru is added on after the other standard cutting is done. Not all features acquire the z thru. Only outlines and holes that go through the part and drilling operations that do the same.

Hello.

I think the others will appreciate it.

Well, I hope so. I find it really helpful.

I think i understood the point.

Basically the “step down” value that I set is not the actual value of the Z dive.
It is just the maximum value of the step down allow by the machine itself. In my case (10 mm stock
and 4 mm step down) the gcode goes to the Z-10 (actually 9.99) with three steps of 3.33~3.34
(maximum values possible to reach 10 mm with increments smaller than 4 mm).
Then, the 2 mm of z thru are applied.

Makes sense… i am not so expert of CNC :frowning_face:

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this is essentially correct

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