Z axis grinding before print start when low

Hi, there is a consistent bug/oversight in the firmware of the X1. I have a 24cm high object that I print fairly regularly. This leaves the bed very low. When I start another print afterwards the bed always lowers and hits the base and there is a horrible grinding noise while I’m assuming the motor is slipping on the belt damaging it. It then raises and carries on normally. I’ve seen this behaviour before every print which is perfectly fine when it isn’t so low, but very bad when the bed starts off at the bottom. I usually manually raise the bed now after printing that object to avoid this but sometimes I forget and it hits the bottom.
This is a serious issue that is causing damage to the machine, and a surprising oversight considering the well polished nature of the software generally.

Don’t worry. After a start, the printer doesn’t know the Z-position. So to avoid scratching the nozzle over the printplate, it lowers the bed a bit with a reduced current to the Z-motor. If the bed happens to be all the way down it hits the lower stop and the motor is loosing steps. There is no slipping of anything and no damage will be done. After 2100 hours of printing, my Z-belt still looks as new.

So this isn’t causing damage? I’m a little reassured but it’s a very loud grinding noise…
Maybe it doesn’t need to drop as far as it currently does before it homes.

The printer doesn’t lower the bed by much, only a few mm. There is one way for you to avoid the noise: If the bed is close to the lower stop, raise it manually before homing or starting the print.

As @Ulrich says it is a normal noise. There have been users that have edited the end gcode to make it not go as far down and Bambu released a firmware that also reduced the chance it will happen. It’s safe to ignore it or as noted above, manually run it up if you want to avoid it without modification.

Aparently the new firmware update sorts this out.

“Headlining Bambu Lab version is a bug fix solving an issue that caused motor skipping when the heatbed was close to the bottom of the printer. This didn’t cause any damage to machines, Bambu Lab says, but did generate noise, which has been eliminated thanks to the fix.”