CK Homing issues

[timmjn]

Hey all,

I have replaced the CK electronics enclusure with a new one, mainly to have access to the abort/hold/resume/estop functions, as well as probing, without adding to the already cramped enclosure. Since I installed it, I am having some weird issues with homing. I will describe the problem first, then the things which I have already tried to fix/locate the problem. I hope someone here can point in me in the right direction.

The problem:

When I press home
- The z axis moves downwards (!!) in two small burst of ~15 mm
- The x and y axes start moving in + direction
- The x axis stops after a few mm
- The y axis continues to its limit switch
- Only the y axis preforms its pull-off and slow approach

That's it, there are no errors or nothing.

The motors are running fine, jogging and running are both working perfectly. Also z moves in the right direction.

What I have tried to troubleshoot:

Initially in thought the issue was interference from the motor wires on the switch wires. Therefore, I replaced the limit switch wires between the machine and the electronics box and the wires inside the box with twisted pairs. No luck.

Then, I rewired the switched to be NC and set $5=1. This didn't change a thing either. I ended up wiring them back to NO, since I noticed the + and - limit pins on the shield are in parallel.

I have turned on hard limits to see if the switches triggered correctly and whether I was having constant false triggers. All switches trigger correctly when pressed. Also, I was getting false triggers (as expected), but not constantly. I can jog the machine around for a few minutes before having a false trigger.

I have by-passed the switches alltogether to see whether it was a GBRL issue. When bypassed, the axis move in the right direction / seem to show correct behaviour. So, the issue is really in the switches.

I am really at loss what could fix this. I had to extend the switch wires (and 1 set of motor wires) a bit to reach the new electronics box, so I soldered on some wire. Could this be the source of the problem?

The only next step I can think of is replacing all wires with shielded cable. 

Any input is greatly appreciated!!

Cheers,

Tim

[Bruce]

Post the GRBL machine settings. You can try to reset the GRBL machine settings by typing: $RST=$
in the console.

[timmjn]

Here are my settings:

$0=10
$1=255
$2=0
$3=0
$4=0
$5=0
$6=0
$10=1
$11=0.010
$12=0.002
$13=0
$20=0
$21=0
$22=1
$23=0
$24=35.000
$25=1200.000
$26=94
$27=4.000
$30=12000
$31=0
$32=0
$100=200.000
$101=200.000
$102=200.000
$110=3500.000
$111=4400.000
$112=3000.000
$120=240.000
$121=240.000
$122=240.000
$130=432.000
$131=432.000
$132=95.000

[Bruce]

These settings look good.

Make sure the stepper motor connection is in the right polarity and are secure.
From top of page 30 of the Carve King Assembly manual: 

[timmjn]

The motor connectors are nice and secure and are in the right direction. I can jog the machine around and even run files without any problems.

[Bruce]

Here is the info on how the homing sequence and motor direction works. 


Homing direction
setting:
The homing directions are controlled by setting $23 setting it to a value defined below:



Axis Homing direction  :Value

X+ Y+ Z+         :0

X- Y+ Z+          :1

X+ Y- Z+          :2

X- Y- Z+           :3

X+ Y+ Z-          :4

X- Y+ Z-           :5

X+ Y- Z-           :6

X- Y- Z-            :7

Default setting ($23=0), the home location is the top right of your work area, with the spindle all the way up.

$23=1 Top left home location.

$23=2 Bottom right of your work area to be the home location.

$23=3 Bottom left.

$23=4 Spindle down home location.



Here is the Homing Cycle Steps described below.

By default, the homing cycle goes through the following steps:

Z axis:
Z Axis will move up (positive) with Fast Rate ($25)
When Z home switch triggered, Z stop for a short time ($26) and back off a distance ($27)
Z Axis will move up slowly util it touches the Z home switch again ($24)
Z Axis backs off a small distance ($27)

X and Y axis:
X, Y Axis move both to Homing direction at fast rate ($25)
The first Axis triggers the switch will stop and wait for the second axis to trigger
When second axis triggers the switch, both axis back off a distance ($27)
Both X and Y axis will move toward switches again slowly, until both switches triggered again ($24)
Both X and Y axis will back off a small distance ($27)

[timmjn]

Thank you Bruce! I read elsewhere that when the switch is triggered at the start of the homing cycle, the controller first tries to pull off. I suspect that's happening with my z axis. Either way, I have ordered myself some shielded cables, I will rewire the whole machine and report back!

[timmjn]

For anyone interested or experiencing the same problem, I totally rewired the machine using shielded cable and everything is back to normal again.