Z axis lowers 5 mm on command G0 Z-5, but also lowers on command G0 Z5

LightBurn Software Questions
1

Hello all,

I’m running into an issue with the Z offset. I can use the up arrow and down arrow to raise and lower the laser. It responds correctly to the up/down arrow and generates the codes ($J=G91G21 Z5 F600 & $J=G91G21 Z-5 F600) to move up or down 5 mm.

Using Z offset, when moving to the next element in a group on the same layer, the code issues a G0 Z1 and G0 Z-1 command, but the laser drops 1 mm at each command instead of raising 1mm then dropping 1 mm to start the next element. Eventually it would contact the work piece if left to run. Whatever the value is, 1 or -1 the laser descends on either command.

I’ve played with the machine settings for the Z axis and get the same results. MY NEJE seems to process the positive G0 Z1 command as a negative. I get the same results for 1 layer with multiple passes and dropping the laser at each pass, or creating multiple stacked layers with Z offset.

Not certain why it responds correctly to the $J=G91G21 Z1 F600, but not G0 Z1, G91G21 Z5, or just Z1.

Any thoughts would be appreciated !

$$

$0=10

$1=1

$2=0

$3=0

$4=0

$5=0

$6=0

$10=3

$11=0.010

$12=0.002

$13=0

$20=0

$21=0

$22=1

$23=1

$24=6000.000

$25=6000.000

$26=250

$27=1.000

$30=1000

$31=0

$32=1

$40=0.200

$41=10

$42=10

$43=0

$100=80.000

$101=80.000

$102=800.000

$103=80.000

$110=20000.000

$111=19998.000

$112=5000.000

$113=3000.000

$120=1000.000

$121=1000.000

$122=5000.000

$123=50.000

$130=750.000

$131=450.000

$132=45.000

$133=100.000

ok

2

That suggests the Z axis speed is too high, causing the motor to stall.

The jog arrow codes set a 600 mm/min speed (Z-5 F600) that’s within the motor’s ability, but ordinary moves (try to) run at the layer speed.

This suggests the controller’s Z axis Max rate is set too high.

Assuming the controller permits config setting changes, knock the speed down to what works. In the Console window, type:

$112=600

You can also set the Z axis speed limit to 600 in Machine Settings.

Let us know the original setting, because it’s always amusing to see manufacturer’s aspirations.

2 Likes
3

Ed, I can’t thank you enough ! That was spot on. That is exactly what was happening and the answer and audible clue were staring me right in the face and I totally overlooked it. I’ve been confounded by this problem for quite a while. I did wonder why the pitch of the stepper motor was so different when the commands were being issued, and the answer is it was being overdriven. The machine settings were $122=5000.000, now $122=600. I tried both variations with multiple passes on one layer using Z step per pass, and multiple layers using Z offset and both now work. The laser head smoothly moves up and down and functions as it should.

Many many thanks for solving this for me !

1 Like
4

That’s definitely aspirational! :grin:

You can try increasing the Z axis speed, but IMO that axis moves little enough it won’t have any effect on the total job time.

Fire The Laser!

5

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