I’m trying to understand the reasoning behind moving build plate down, then slightly up
For example, when you start a job, it moves z-motor down 30mm, then it moves up 25mm, then moves head to the poopschute, waiting for the nozzle to heats up. In this move, since it doesn’t use any sensors, if built plate is less than 30mm from the bottom, it crashes with the bottom makes the z-motor belt/pully to slip with horrible noise. I don’t think this is a good for the printer, especially if you print a lot of large prints. So why not simply move 5mm down?
Same thing after finishing the job, it moves the plate down, but at the end it moves up a few mm - why???
Loading filament = it moves from poopschute to front right corner, then front left and back to poopschute…wtf!
Not to mention every job startup it makes so many unnecessary movies.
That’s a frequent topic of discussion that has many of us bewildered. Bambu eventually responded.
The general consensus is twofold. The initial downward movement is a basic safety maneuver to ensure that whenever the printer stops, whatever was on the build plate is moved safely below the nozzle tip. That makes sense because the system is essentially blind to what precisely is under the nozzle, spaghetti detection aside.
The second theory is that Bambu was either too cheap or too lazy to add a $0.15 limit switch to provide a mechanical signal to the controller that the build plate has reached the bottom.
One person did report that they got a message from Bambu and that they assured them it was normal. In a later release Bambu added a feature into the firmware that would minimize the grinding sound when the plate hit the bottom, not eliminate but minimize.
Thank you. They don’t really need a physical switch; they could use the same type of sensing as when plate is homing home - sensing resistance. This still doesn’t explain the “overshooting”…
@silver118822
No, I’m on 01.08.05.00 (20250312). This was supposedly fixed in 01.06.00.00 (20230801), but I’m still getting this issue. The gcode does use G380 commands that supposed to fix this. Unfortunately, the way bambu is heading, I’m not planning on upgrading to annoying new firmware where everything now is hidden behind menus.
