Success after third day
Ordered my MK3 and MMU2 back in Sept 19 - have been enjoying the MK3 for the last 7 months.
Was close to cancelled order and going for a palette2pro instead - but the MMU2S finally arrived about 3 weeks ago. Took me a few weeks to find some spare time and pluck up courage to start on the build.
Starting building it on Mon, the extruder upgrade took several hours the first day - main trouble I had was firstly getting out the old heat block - eventually managed to wiggle it out. Also had trouble screwing up bondtech as screw a little stripped - couldn't get screw in far enough for flat part of shaft - some tightened on rounded part (more later on this). Also found the sensor checking step quite hard.
Took most of Tuesday to put together the MMU2S - no particular problems with build - excellent instructions and really enjoyable day - apart from cutting my finger on the blade - when it was getting in the way of moving the carriage - so removed it.
First attempt at loading filament seemed to work ok - I used the load to Nozzle option. But after that couldn't get it to load filament at all - so finished the day quite disillusioned. Tried loads of different things - including downgrading of MK3 firmware.
Also on first day found loading the buffer very tricky.
Overnight decided it might be the Bondtech slipping - so took door off - which is more tricky than before due to new IR sensor and chimney.
Was relieved to find that the bondtech was loose - but the allen key part of the grub screw was rounded so I couldn't tighten it enough.
Searched around for replacement thumb screws - and put a 3mm long one in initially from slot 5 on the MMU2.
Unfortunately this didn't work - as the screw was sticking out and pushing the other bondtech gear away once per rotation.
Found another grub screw the same size on a spare belt gear, and as the allen key hole went a long way in decided to file some of the back off - quite hard - but eventually got it short enough to fit without protruding. After that loading to nozzle seemed to work ok on firmware 3.6.0, and also when I re upgraded it again to 3.7.0.
Filament seem to snap off in buffer - so decided to ditch buffer - and initially have nothing other than the bowden tubes and supplied filament rollers - will print a few auto rewind spools once printer working.
Next problem was z offset - took a couple of hours trying to get it right again - before giving up for the evening.
Also quite a few problems with jams etc, and managed to snap the filament off when the carriage moved.
Next day (today) - remembered the G coded z offset from this thread
and all seemed to work.
Was still getting jams - but seemed to work more reliably if it didn't load to nozzle.
Switched profile to Chris W's MMU2 Pretty PLA - loaded the file as configuration then saved it back out as separate Print, Filament and Printer subsets.
Finally ready to try a multi material print after a couple of hours today - loaded slot one with silver prusament, and slot two with green aldi PLA+ filament - and loaded just a couple of separate objects and just coloured them differently.
Hooray - it worked fine - so first print successful - only a very basic print with only about 6 colour changes - but now quite pleased - and confident to build a more advanced print.
My main things to try next are
1. a proper multi colour print - maybe of the auto rewind spool holders first.
2. mixed flexible and rigid PLA, and
3. soluble supports.
Main lesson I have learnt so far is be very careful of 'load to nozzle' - and make sure that I fully remove filament and re-cut it before trying and further MMU2 control. Main pet hate so far is the idler homing noise - I hope a way is found it the future to make it a bit quieter!