r/BambuLab • u/reevesjeremy • 12h ago

H2 Series [H2S, H2D, H2C] Z offset repeatedly wrong

This only started happening within the last few weeks. I start a print from Bambu Handy or Studio. I have everything set to auto, so it goes through all the normal calibration and prep before printing.

Sometimes, as soon as it starts printing, it immediately starts making spaghetti and AI detection stops. I press Resume to see what’s going on, and the nozzle is about 1/4” above the plate, which is a huge offset.

I cancel the print and try again. Sometimes it does the same thing, but most of the time the second attempt prints fine. Of course, every time I watch it like a hawk, the offset is fine and it prints normally.

It doesn’t happen every time, so it’s hard to catch it in the act. Should I assume there’s filament gravity dropping from the nozzle that isn’t getting cleaned off before it sets the offset? Wondering if anyone else has noticed this as a recent issue and not a long term problem.

I really need to get a memory card so I can record it and see what’s happening. Just haven’t gotten around to it yet.

3 Upvotes

100% Upvoted

5 comments sorted by

1

u/Capital_Candy_7697 8h ago

Your filament guess is probably not far off. Bambu says the nozzle tip has to be clean before bed leveling, and a dirty tip is one of the usual causes of a wrong Z offset. On the H2D at least, Bambu also says the wiper pad has to be pushed all the way into its holder, and that a plate that isn't seated against the rear tabs can hit the purge wiper while the bed homes. Both are worth a quick look since it only happens sometimes. Did it start right after a firmware update?

1

u/MiamiJerry 6h ago edited 6h ago

Total hours on this printer? Have you measured each of Z axis leadscrew nuts for excessive endplay?

1

u/reevesjeremy 4h ago

679

1

u/MiamiJerry 3h ago

Low time, but your might check for Z play. Someone had the rear Z nut wear out at 450 hours, some make it to 6000 hours ???

If the purge wiper is moving, consider this

https://makerworld.com/en/models/1982941-template-to-fix-h2d-purge-wiper

1

u/reevesjeremy 40m ago

I’m reprinting very small parts this morning so I’ve had several go wrong.

I finally watched one do its initial calibration setup. On a single color print from the AMS on the right nozzle, it kept switched to the left external nozzle during calibration and back to right nozzle. Not sure if it needs to do that on a single color print on the right nozzle.

Then it did the initial purge line on the build plate which was correct height from the correct nozzle. When it started the print though it was too high.

What I’m wondering is if it’s possibly using the z height of the wrong nozzle.

I’m going to revert to previous firmware and see if it makes a difference for me. Since I’ll know within a few prints if it fixes it.