If you are seeing the Z-axis drop slowly, plunge into the material, or cut to inconsistent depths, we suggest these following questions to prioritize your troubleshooting. If none of these apply, go to Mechanical Check
- Are you using a spindle?
- Have you surfaced your spoilboard?
- Does the toolpath match what you intended? Use ncviewer.com to check
- Are you using Fusion 360 and if so, did you change safe retracts to clearance height?
- Jog the machine to the depth of cut you need for the material - is the machine bottoming out?
Spindle
The weight of a spindle can lower the z-axis when cutting. In the firmware you can enable the Z motor to stay energized when stopped, which will counter the weight.
For the LongBoard controller, change setting $1 Step idle delay to 255ms.
Note: this will enable all motors and they may get hot during operation
For the SLB, grblHAL firmware has the option to enable specific motors, which prevents the other motors from overheating during cutting. On $37 Steppers deenergize, toggle ON the Z axis. In the console or diagnostic report, this will show up as $37=4
Spoilboard
Make sure your MDF wasteboard has been surfaced. This surface can also warp over time, so it may be necessary to surface this again if not done recently.
Toolpath
If the issue is consistently the same depth and the same spot, it's likely your toolpath. Check your toolpath settings first and ensure you are using the correct post-processor.
Fusion 360
To avoid potential issues with Fusion 360, we recommend you make the following checks to your post processor:
- Change the ‘Safe Retracts‘ to “Clearance Height” and NOT “G28”. It will be obvious that you have this on if you don’t have limit switches or forget to home your machine and at the start of the job your bit plunges suddenly really deep into your material
- Output M6 set as “No” (unless you plan to set up tool changing)
- Output Tool Number set as “No” (unless you plan to set up tool changing)
Bottoming Out
Lower the position of your router at the router mount, or use a longer end mill.
If none of the above apply to you, please review the following mechanical and motor/driver checks:
Mechanical Check
Coupler - Ensure that the coupler set-screws on the Z-axis assembly are tightened, on both the motor and leadscrew sides.
ACME nut - Ensure the ACME nut is oriented so the shoulder is making contact with the flange bearing. The Z-axis lead screw should not be able to slide up and down.
Linear guides - Check for any play, dust or binding. We recommend using a 3-in-1 oil and a shop towel to clean and lubricate them. To test, raise the router to the top and remove the two screws holding the backlash nut to the gantry plate. Push the Z gantry, it should travel freely on the linear guides.
Flange bearing - Ensure that flange bearings are rotating freely, the inner race isn't binding
Anti-backlash nut - The leadscrew should rotate with little difficulty by hand. Adjust the tension of the anti-backlash screw, and/or loosen the two M5 mounting screws.
Motor and Driver Check
- Swap two motor connectors at the controller end, and see if the issue moves. If it moves to a different axis, it's likely the motor or harness. If it doesn't move, it could be the board or the harness.
- Check for burned or discoloured connectors on the motor and harness. This can indicate a short.
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If you have the SLB, check that the following firmware settings are correct:
$102 Z-axis travel resolution = 800
$142 Z-axis motor current = 2800
$152 Z-axis microsteps = 32 - If you have the LongBoard, check that the potentiometers are all set correctly: the 2 divets surrounding one end of the cross, that end should be pointing around 11 o'clock. Unplug your machine from power before adjusting this with a small screwdriver.