Issue swapping hotend

[csader]

After my Jhead melted down on me, I'm swapping out for a hexagon (and soon for clough42's dual). But last night I got everything installed and set my ABL offset. Now when I try to print, ABL works great, then the print starts and the hotend hovers about 10mm above the heat bed...I've double checked my offsets, and everything seems to be right.

I'm going to tinker more tonight, but thought I would check with you fine folks in the meantime.

[MiniMadRyan]

After flashing your firmware, have you issued an M502 command to 'factory reset' the settings? I found I had the same issue you're describing, and it wasn't until issuing an M502 did the correct offset and changes i made work correctly.

[clough42]

After flashing your firmware, have you issued an M502 command to 'factory reset' the settings? I found I had the same issue you're describing, and it wasn't until issuing an M502 did the correct offset and changes i made work correctly.

It looks to me like after the M502, you also need to issue M500 to store the defaults.

If you're still having trouble, make sure you have your max endstops disabled in Configuration.h. I've seen scenarios where they're enabled, but disconnected, with pullups disabled, and they false-trigger when the servo retracts the probe. This causes the ABL to abort and leaves the Z offset in the wrong position. This is intermittent, and can be very confusing when trying to debug something else.

[csader]

I'll give this a shot, thanks.

Clough, what are pull ups? (Sorry...)

[clough42]

I'll give this a shot, thanks.

Clough, what are pull ups? (Sorry...)

The microcontroller input pins have resistors between the positive power rail and the input pins to pull the pins high when they aren't connected. This allows you to connect a switch between the pin and ground and get a reliable input signal (high when the switch Is open, low when it is closed).

These pullup resistors can be enabled or disabled in the firmware. If the pullups are disabled and nothing is connected to the pin, you can get inconsistent values when you try to read the pin state.