G-CODE G90, SCANNING OFFSET ADJUST

[masterkuka (Andris)]

Hello

I’ve purchased a g-code license, the program is very good.
2 things you would like to find out.
1:
I use a program for engraving,
I need to engrave the “tape measure” on the aluminum profile.
Nowhere to find how to save g-code with G90 (Absolute cords)
G91 doesn’t work for me because there is an error on the 3m engraving

2:
I’m not clear about “SCANNING OFFSET ADJUST”
my machine’s line offset error is not linear
entering 6 entries in table “SCANNING OFFSET ADJUST”
10mm/sec = 0.150
30mm/sec = 0.445
50mm/sec = 0.665
100mm/sec = 1.100
120mm/sec = 1.300
150mm/sec = 1.590

• calculation wrong line offset

; Scan @ 10 mm/sec, 100% power = Y0.3 // OK
; Scan @ 30 mm/sec, 50% power = Y0.89 // OK
; Scan @ 50 mm/sec, 100% power = Y1.48 // wrong
; Scan @ 100 mm/sec, 100% power = Y2.96 // wrong
; Scan @ 120 mm/sec, 100% power = Y3.55 // wrong
; Scan @ 150 mm/sec, 100% power = Y3.18 // OK

/// SAMPLE //
; LightBurn 0.9.04
; Marlin device profile, absolute cords
G21
G90
; Scan @ 10 mm/sec, 100% power
M05
G0 X3.06 Y11.87 F9000
G91
M03 S24000
G1 Y-10 F600
M03 S0
G1 X1 Y0.3
M03 S24000
G1 Y10
M03 S0
G1 X1 Y-0.3
M03 S24000
G1 Y-10
G90
; Scan @ 30 mm/sec, 50% power
M05
G0 X14.79 Y11.72 F9000
G91
M03 S12000
G1 Y-10 F1800
M03 S0
G1 X1 Y0.89
M03 S12000
G1 Y10
M03 S0
G1 X1 Y-0.89
M03 S12000
G1 Y-10
G90
; Scan @ 50 mm/sec, 100% power
M05
G0 X24.79 Y11.42 F9000
G91
M03 S24000
G1 Y-10 F3000
M03 S0
G1 X1 Y1.48
M03 S24000
G1 Y10
M03 S0
G1 X1 Y-1.48
M03 S24000
G1 Y-10
G90
; Scan @ 100 mm/sec, 100% power
M05
G0 X34.18 Y10.58 F9000
G91
M03 S24000
G1 Y-10 F6000
M03 S0
G1 X1 Y2.96
M03 S24000
G1 Y10
M03 S0
G1 X1 Y-2.96
M03 S24000
G1 Y-10
G90
; Scan @ 120 mm/sec, 100% power
M05
G0 X40.99 Y10.09 F9000
G91
M03 S24000
G1 Y-10 F7200
M03 S0
G1 X1 Y3.55
M03 S24000
G1 Y10
M03 S0
G1 X1 Y-3.55
M03 S24000
G1 Y-10
G90
; Scan @ 150 mm/sec, 100% power
M05
G0 X50.38 Y10.17 F9000
G91
M03 S24000
G1 Y-10
M03 S0
G1 X1 Y3.18
M03 S24000
G1 Y10
M03 S0
G1 X1 Y-3.18
M03 S24000
G1 Y-10
G90
M05
G90
; return to user-defined finish pos
G0 X0 Y0 F9000

[LightBurn (Oz)]

@masterkuka

G91 doesn’t work for me because there is an error on the 3m engraving

“An error”? Could you elaborate?

LightBurn uses G91 for scanning because the code tends to be much smaller, and I internally track the precision errors caused by rounding and account for them. If you are using normal cuts, or a series of scans, and using Absolute Coords as the mode, LightBurn will emit G90 / absolute moves in between, then flip to G91 / relative moves for scans within the job.

I’m not sure what you’re getting at with the scanning errors. You’ve provided two tables of numbers, but haven’t told me what they mean, and I’m not sure what the sample GCode is supposed to represent. What are you trying to show here?