Slight Grinding in MMU3 during Filament Loading
Upfront I am getting far better outcomes with my MMU3 after upgrading from MMU2S and am running far longer duration successful prints, however
I am observing on a filament load what appears to be a delay in disengaging the MMU idler when the filament has triggered the IR sensor at the extruder which then stops but the MMU is grinding the filament for a short time after that (subjective guess but estimate 2 to 3 hob teeth jumps). This is grinding the filament and causing a build-up of detritus in the MMU (which eventually gets everywhere in the filament paths). It seems to me that there is a timing/software issue here? Attached photo shows what has been caused in a recent print of 538 tool changes.
I would like not to be cleaning the machine as much to remove this detritus.
I have triple checked the tensions of extruder and MMU adjustments as well as the IR sensor chimney position and all are as recommended by Prusa.
My configuration is
Mk3.5 (FW = Mk35_6_0_0), MMU3 (FW= MMU3_3_0_3), REVO equipped, Octoprint (V 1.10.0)
Appreciate any views, similar observations or corrective actions to assist (or escalate)
thankyou
Barry
RE: Slight Grinding in MMU3 during Filament Loading
I am also having this issue. Except it is causing filament loading to fail altogether. Spent an entire day trying to get it to not do this, unsuccessfully.
RE: Slight Grinding in MMU3 during Filament Loading
By chance was the filament white? If so, I and another have experienced it as well as noted in another thread.
RE: Slight Grinding in MMU3 during Filament Loading
My issue is not constrained to white and is specific to the end part of the loading sequence due to the MMU still trying to push filament towards the extruder when it had stopped (but of course can lead to a failure for an unload). The problem really multiplies when the print has many short colour changes per layer. I am running a Mk3.5 with the old extruder rather than what you would have with a Mk4 or Mk3.9 and perhaps there are different characteristics of extruders at play here. I am still trying to diagnose but have not been doing much multimaterial printing of late.
I have mitigated the problem by backing off both MMU and extruder tension even more than the Prusa recommended setting but the grind still occurs.
In terms of white being more susceptible it may be slight softer than darker colours though I have had issues also with light blue and pink that seemed to grind more if the tension is too high. You may also want to check the diameters of the filaments with a vernier to see if that is a factor.
Also (for my issue) have you observed any grinding of the filament on load at the MMU as I described in the original post.
thanks
Barry
RE: Slight Grinding in MMU3 during Filament Loading
Yes, I've experienced the grinding, but just once. Here is the thread where I and another user describe our issue and he posted pictures which look like what I experienced.