Filament Sensor  

RE: Filament Sensor

Just had the same issue. I deliberately set up a print that would run out of filament to test the system. It just hung at the filament change screen. Tried the magnet trick - no help. Reading through this thread doesn't seem to have a guaranteed solution. It's a pity it was one of the features that I thought was really worth while on the Mk4. Not worth it if it's not reliable. Does anyone form Prusa monitor this forum to address these issues??

RE: Filament Sensor

An interesting read - thanks!

So seems like this is something that can be fixed via firmware, which is good news. Hopefully they will roll the update out soon for all users...

RE: Filament Sensor

Well, it’s reassuring to see others have experienced the same problem (as in “So it’s not just me, then”). My (upgraded to)Mk4 has started performing the same way. When the filament runs out the printer detects this and offers up the Nextruder for more filament but on inserting it, I get a “Filament appears to loaded already” message. Nothing for it but to cancel the print.

On releasing the clip and swinging the idler away I see the filament has broken and the end of the filament can be seen just disappearing down into the hole that leads to the nozzle. Feeding in a new filament and guiding it to butt with the stuff already in the nozzle – and manually applying pressure to the idler - enabled the ‘blockage’ to be expelled and then did a normal unload.

I've tried to clean the little of the feed gear I can see and I've done a sensor recalibration. 

At least I can continue printing. But I’m going to try to avoid having to change filament in flight.

I hope this issue can be resolved by a firmware upgrade – and as soon as possible, please.  

RE: Filament Sensor

I have a new MK4 kit (late Jan 2024).

I was in the middle of a print and a colour change was triggered in the code. After removing the filament the printer was stuck on the “Changing Filament” screen at 0%.  

I got past this by removing the side panel covering the cables for the filament sensor and touch sensor then unplugging the filament sensor (three white cables) from the board with needle nose pliers.  It allowed the filament change to continue. Plugged the cable back in and it continued. Saved the print. 

Will look at disabling this faulty sensor. Disappointed with it.

RE: Filament Sensor

Thx that saved me a day

RE: Filament Sensor

Just ran into this issue today. For me it was a partially clogged nozzle. Between the net throwing around mechanical and software issues, the MK4S actually printing lines, and of course my wopping 2kg's of prints behind me, I was confused as to what this could be/what to do? So I disassembled the Hall sensor for inspection; clean as a whistle. But, evidence of a rough filament end when unloaded, and some filament residue attached to the drive gear made me think, "What if the filament can't get pass thru the nozzle at it's programmed flow rate?". So I spent the morning cleaning that expensive nozzle (hard .04 obsidian, and the other brass I have). Then yeah, works fine (hope it last along time). 

side note: the last 2 shipments of filaments, PLA and PETG, from the company I buy from were filthy, I mean dirty like dusty from sitting out for  months. it is not impregnated into the filament, just covering it. But as I used it I could see new dust and small debris revealing itself every few rotations of the roll. hmmm?  Not gonna say who yet cause I believe every person has the right to face their accuser. So gonna call and discuss with them 1st. Could just be something innocuous and is all fixed. Remember sometimes a couple months can pass between orders. For now, I pushed the filament thru a small piece of dry sponge, then trapped that at the bowden tube inlet to use as a wiper. Yeah it gets dirty.

RE: Filament Sensor

Had filament stuck sensor problems, unloaded filament PLA, found long tails on it, reduced nozzle temp to 210 from 220 - problem solved. Seems like the higher temp caused filament higher up in the nozzle to melt causing the error, lowering the temp seems to have cured it.