First layers are great, then terrible
I've been battling the MMU upgrade since I got it. The printer was factory assembled. I followed the instructions to a T (retired army, can do checklists). I set and reset the idler tension springs with calipers. I've cleaned the entire feed path. I've replaced the heat block, heat sink, heat break, nozzle, PTFE tube (on the fourth tube, this one from Prusa after my DIY attempts didn't help... #ShippingCosts). I've set the PINDA spacing and did the live z adjust (using a large magnifier glass... It's good). This printer was rock solid, now I can't complete anything. I've tried everything I could think of and everything Prusa support suggests. Please give me ideas to try because I'm fresh out.
The attached photos show my latest print attempts. The Benchy was from Prusa's gcode for MMU (single filament). The first one failed after 4mm (extruder gears started grinding / skipping, no feeding out nozzle). I did two cold pulls with nylon and then started the second. I watched it for an hour then went to bed and woke up to a Benchy that started out great and then progressively had less and less filament (the roof wobbles like the top of a Canadian's head in Southpark).
Re: First layers are great, then terrible
Feed path resistance, which is a really common problem.
If you can narrow it down to the multiplexer, try replacing it with this:
Re: First layers are great, then terrible
Have you tried other filament? I found original PR sometimes has sections that are a bit wider. In my case I actually measured diameters along several meters before printing, all fine, only to find thicker spots further into the spool. Two of my PR PLA spools have this problem (worst diameter I found was 1.87). If that happens filament will rub against the steel tubes in the MUX, randomly increasing resistance.
Re: First layers are great, then terrible
That fixed it! Haven't tested MM, but at least I can print with 1 material again!
Re: First layers are great, then terrible
Have you tried other filament? I found original PR sometimes has sections that are a bit wider. In my case I actually measured diameters along several meters before printing, all fine, only to find thicker spots further into the spool. Two of my PR PLA spools have this problem (worst diameter I found was 1.87). If that happens filament will rub against the steel tubes in the MUX, randomly increasing resistance.
Yeah, I tried other brands and invariably I would run into the same problems in the multiplexer (except for smaller calibration prints), Anything over and hour or so jammed.