For my winerack i engraved some wooden panels.

When doing so, i needed to fix the height of the engraver to get the focus of the beam right.

At start i removed all Z positions from the GCODE file after calibrating. Later i used a script wrote that fixed the height setting to 110.

#!/bin/bash
# Usage: confirm height focus at 110
# ./scriptname filetofix.gcode
myz=110
cat "$1" | sed s/Z1/Z${myz}/g | sed s/Z6/Z${myz}/g > "fixed.$1"

Another tool i made is the one below, it takes a GCODE file, calulates where the borders are (min/max x and y)
And sets the FAN2 (laser intensity to a minimum)
After that it generates GCODE to draw a box wherein the to be engraved object is made

Now you can run the GCODE file multiple times to position it on the wood to you can get the minimum of spoils.

#!/bin/bash
# Usage: scriptname file.gcode 
# It wil create a pointtest file for test running
myz=110
MAXX=$(cat "$1" | grep "G0 X" | awk '{ print $2 }' | cut -c2- | sort -n | tail -1)
MINX=$(cat "$1" | grep "G0 X" | awk '{ print $2 }' | cut -c2- | sort -n | head -1)
MAXY=$(cat "$1" | grep "G0 X" | awk '{ print $3 }' | cut -c2- | sort -n | tail -1)
MINY=$(cat "$1" | grep "G0 X" | awk '{ print $3 }' | cut -c2- | sort -n | head -1)

cat > "pointtest - $1" << EOF
;BingoStart
G90
M17 Z
G0 F3000
G0 Z${myz} F3000
M18 Z
G0 X${MINX} Y${MINY}
M106 S2
G0 F3000
G0 X${MINX} Y${MAXY}
M106 S2
G0 F3000
G0 X${MAXX} Y${MAXY}
M106 S2
G0 F3000
G0 X${MAXX} Y${MINY}
M106 S2
G0 F3000
G0 X${MINX} Y${MINY}
M106 S2
G0 F3000
G0 X${MINX} Y${MAXY}
M106 S2
G0 F3000
G0 X${MAXX} Y${MAXY}
M106 S2
G0 F3000
G0 X${MAXX} Y${MINY}
M106 S2
G0 F3000
G0 X${MINX} Y${MINY}
M106 S2
M107
;end
EOF

GCODES

• M17 Z – disable Z movement
• G0 – rapid move
  G0 X100 Y100 (Goto 100,100)
  G0 F3000 (speed)
• M106 – set fan speed (I my case, this is laser intensity)
  M106 – S2
• G90 – set absolute coordinates
• M107 – fan off

More info about gcodes: http://www.science.smith.edu/cdf/pdf_files/Techno_GCODE%20Commands.pdf