MK4s/MK4 Filament Loading Click of Death  

MK4s/MK4 Filament Loading Click of Death

If you have a Mk4/Mk4s and have been doing a lot of filament changes, watch out. If you hear clicking when you load a filament, stop, unload and do not try again until you have read this.

I have had my Mk4s (upgraded from a Mk4, but the issue is relevant to both) for a couple of years, but recently I printed about 40 items that needed 4 filament changes per item, so 160 filament changes. As I was completing the project, the MK4S started to struggle to load filaments with loud clicking sounds unless I cut a really steep angle on the end of the filament and held the slope at a certain angle. If I looked inside the idler lever, the filament would be going around or under the driving gear. After a series of failed attempts, I finally loaded the filament but the nozzle test failed.

To cut a long story short, all my filament changes had worn away the hole in the bar in the main plate through which the filament travels having passed the driving gear (photo below, the left is normal, the right is the worn away bar). So the filament was passing under the gear and had been battering away at the load cell circuit board in the heatsink assembly and had wrecked it.

What was confusing was that I could eventually load a filament, but the nozzle test was failing. But if I did a nozzle tap test - it would pass. The loadcell readings were changing if I pressed on the nozzle but I’m guessing not the right numbers for the system. On dismantling the printhead, I found the damage to the circuit board (photo below).

So the lesson is if you start getting clicking when loading filament, stop and have a careful look at the main plate bar behind the idler lever. If you can, you should probably print and replace the main plate. If you persist, you could end up having to order a new heatsink assembly - along with shipping fees, tariffs, etc.

Hope helps someone.

I do wonder how the system copes in the long term with multiple filament changes with an MMU, maybe the melted end has a smoother shape to ease its passage through the print head.