X Axis Travel Issue

LowRider CNC Troubleshooting
6

I am happy to report that I uncovered the problem. It was a loose connection to the extension for the X axis stepper motor. I used the “S” strain relief technique but apparently did not do it very well. I was happy to find the issue.

I did a few more test cuts and then cut out my struts. I just finished installing them and tomorrow I will wire everything back up. Lots of wire clean up. I also think I will eliminate the connectors between the stepper motors and the extension cables. I don’t see why I shouldn’t just solder in some splices and then not have to count on a connection wiggling loose.

Thanks for convincing me to dig deeper. I was ready to buy a new stepper motor and rebuild the core. I am so glad that is not necessary.

I did do some additional tests with the help of Gemini. I pasted in the $SS and Gemini told me that my X Axis driver was working well. I also moved the x axis cable to a Y axis driver to see if that would move the machine. It did not so that further confirmed that the problem was from the X cable connection at Jackpot back to the motor.

Here are the steps I took:

  1. Send $X: If the machine is in an Alarm state, send $X to unlock it, then try moving it again.
  2. Disconnect the Endstop: Temporarily unplug the X-endstop from the Jackpot board and try to move the axis. If it moves fine, you have an electrical noise issue on your limit switch line.
  3. Swap Drivers: Since the Jackpot uses plug-in drivers, power down, swap the X driver with the Y driver, and see if the problem follows the driver or stays on the X-axis.

Gemini suggested the following when I reported that swapping the drivers did not result in movement:

The Verdict: Open Circuit or Mechanical Jam

Because the motor didn’t move even when plugged into a known-working port (Y), one of the following is happening:

  • Bad Wiring/Extension Cable: This is the #1 culprit. If one of the four wires in your stepper extension cable is loose, crimped poorly, or broken, the motor will either vibrate in place, “cog” (move a tiny bit and snap back), or do nothing at all.

  • The “LR4” Mechanical Lock: Since the LowRider 4 uses a belt-and-pulley system for X, check if the carriage is physically jammed. If the motor is trying to turn but the gantry is wedged, it will simply stall.

  • Failed Motor: While rare, the stepper motor internal windings could be damaged.

I was then directed to complete a step-by-step hardware test:

To find the exact break in the chain, try this sequence:

  1. The Direct Plug Test (The “Golden Rule”):

    Unplug the X-motor extension cable from the Jackpot board. Take the X-motor physically off the gantry (or bring the board to it) and plug the short lead coming directly out of the motor into the Y-axis port on the board.

    • If it moves: Your extension cable is bad. Replace or repair the crimps.

    • If it still doesn’t move: The motor itself is likely defective.

  2. Check the Pins:

    Look at the 4-pin connectors on your X-axis extension cable. Ensure no pins have “pushed out” of the plastic housing. This is very common with JST or DuPont connectors used in DIY CNCs.

  3. Resistance Check (If you have a Multimeter):

    • Unplug the motor from the board.

    • Measure resistance across the pairs (usually Pin 1 & 2, and Pin 3 & 4).

    • You should see a low resistance (usually 2\\Omega to 5\\Omega). If you see “OL” or infinite resistance on either pair, you have a broken wire.

I didn’t need all these steps since I found the problem in the extension connection.

Looking forward to getting this thing put back together and start on a string of projects I have been dreaming about doing. More on that later.

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LR4 Bulldog Edition