Different Prints Failing at the Exact Same Height
The printer was printing fine for weeks until it crashed into a print. I inspected and recalibrated then ran a Benchy to test and it fails at the exact same height. After making sure the nozzle was fully seated, checking the pinda height and inspecting for obstructions I tried another benchy and got the same results on the exact same height. The Z screws are straight and not touching the top plastic parts. It prints perfectly up to a specific height then knocks the print off the bed. No idea where to go from here. I'm using PLA. Any thoughts would be appreciated!
I haven't printed a benchy and watched at the exact time it crashes but I do know it knocks the print off the bed. Tomorrow I can reprint a benchy and film the exact moment of impact if that would help.
RE: Different Prints Failing at the Exact Same Height
Looking at the benchy picture, it looks like it is two different heights, by about 1 or 2 layers, looking at the curves for the door and window.
Check the Z screws for any debris. Make sure they are clean. Make sure that the rods are also clean and lubricated.
Create or find a simple vertical tower to print for testing to save time.
RE:
Yes, check the Z-axis mechanics. It can be difficult to assemble when building a kit, where the Z axis threaded nuts are not perfectly perpendicular with the print bed and get stuck. Loosening and realigning them possibly helps. Also check that the Z-axis calibration did result in a flat print bed (run up to Z=1, then use the nozzle and a ~1 mm thick piece of cardboard underneath as gauge against the print bed. Turn rods for a "manual Z-axis calibration" that is more accurate than the printer's default one (as it cannot control Z axis motors independently beyond running them all into the end stop). Also, I'm not sure if the manual recommends to lubricate Z-axis rods or explicitly tells to not lubricate them (I guess most people do the latter...)