LR4 Homing and Setup Troubleshooting

LowRider CNC Troubleshooting
1

Hey all!

Firing up my LR4 for the first time and I’m running into some issues.

I’m able to home the X and Z axis but when I try homing the Y axis I get this error.

ALARM:8
Homing fail. Pull off travel failed to clear limit switch. Try increasing pull-off setting or check wiring.

Not sure how to diagnose or fix. I’m able to move the LR4 regardless and decided to press forward and check for squareness. My diagonals were 278.2 and 279.6 cm. Given the large difference, should I enter in something like M666 Y14 or should I move the endstop closer?

Also while trying to Z level, I get another error that says undefined feedrate so I’ve been scratching my head a bunch.

Any help would be greatly appreciated!

2

Are both of your end stops in the same place and could they be crossed at the board?
I would adjust by the stops first leave the pull-off stuff alone for now you can fine-tune that stuff when you get more acquainted

3

Are both of your end stops in the same place and could they be crossed at the board?

If I am facing the router, the endstop on the left triggers about 1 mm earlier than the endstop on the right. When I hit home while both endstops are triggered, it moves away far enough that both limit switches are cleared but the error still occurs and I have to clear it.

They don’t appear to be crossed at the board

4

Use the FluidNC $LIMITS command to sort out limit switches, as described in the link below:

http://wiki.fluidnc.com/en/config/homing_and_limit_switches#testing

We need to make a “post-assembly checkout “ section of the docs.

5

Super helpful. Here’s the shortened output when I run that command with none of the limit switches actuated

Homing Axes : xyz         
Limit Axes :             
  PosLimitPins NegLimitPins Probe
:               y          
:               y          
:               y          
:               y          
:               y
:               y          
:              xy          
:              xy          
:              xy
:               y     Y    
:               y     Y    
:               y     Y

The limit switch for the x axis works fine and the y axis on the right side when facing the router. However, the limit switch on the left side doesn’t seem to be doing anything and according to the fluidnc documentation, this doesn’t seem normal.

Edit: the spaces in the pasted output above are removed when I post so it doesn’t line up properly

6

If you manually press and release the limit switch on the end stop that isn’t working, does the LED on the jackpot turn on and off?

Do you have a DMM to test with?

Can we see pictures of your controller as-wired?

7

You can fix that by using block quotes. Start and finish the selection with 3 back-ticks (`) like so:

: y
: y
: y
: y
: y
: y
: xy
: xy
: xy
: y Y
: y Y
: y Y

This can be used for program code, gcode, or things that have embedded special characters that the forum software wants to interpret as bullet points, or start/stop italics or underscores.

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8

Ok, when I manually press and release the limit switch, all of the switches, except for the y switch on the left side, causes the associated LED to turn off when pressed and turned back on when released. The led for the left-hand side y switch is off. If I connect the two pins together with a metal object, the led turns on.

Is it safe to assume that this y-limit switch is the culprit? I have not tried testing with a DMM but I have tried reseating all of the switches on the board just in case.

20250613_103726
20250613_1037261920×1440 272 KB

9

Sounds very likely that there is a short circuit in the wiring, or at the switch.

Have you tried plugging the switch into a different port to see if the behaviour follows it?

10

I edited that post to add block quotes.

2 Likes
11

Yup, I moved the X limit switch wiring over to the Y and vice versa and can confirm that the behavior follows it. I guess I need to get a new limit switch

12

Do you have an extension?

That is the Most common spot for issues.

If not, check crimp or solder at the switch, second most common issue. The switches themselves seldom go bad.

13

A short in the wires will cause the same symptom and is more likely. Or the wire touching the NO pin on the switch. I’d definitely check to wire separarely from the switch.

14

Ok I whipped out the multimeter and indeed there is a problem somewhere in the wires. No issues with the switch but there’s a disconnect somewhere but I can’t tell where cause the wires are neatly zip-tied, bundled, and out of sight. Replacing the wires to the switch should do the trick! Hopefully I have spare wire lying around since I don’t have any extensions …

1 Like