Please include IR sensor adjustment as a regular assembly step for the MK3S/MMU2S kits
Just upgraded my MK3 to a MK3S with an MMU2S that showed up last week (5 months since purchase, but in line with the more recent estimate tables). Assembled everything, instructions were pretty consistently detailed and clear (it would be nice to know that screws/some plastics aren't needed again from the MK3 extruder disassembly, but it was clear when a specific part needed to be kept for reassembly), checked my work, and thought I had everything right. Powered it up, ran through the calibration wizard, got to Z height calibration, and immediately ran into issues. First no loading, then it loaded and left the heated extruder on the bed while extruding a nice bead all around the nozzle while reporting a filament load error. Not much information from the MMU2S (just the blinking light), very little extruder motor activity, very little detail on the front screen as to what to do, and total softlock in the z height fine adjustment step when it gets stuck confused like this.
Eventually, after looking back through the materials online and in the book I found that this could be related to the IR sensor, and I checked the readout and confirmed it, but this is a very discouraging first power up for an upgrade to a reliable, well described printer that seemed to address everything in the directions. As it turns out, the IR sensor adjustment can be VERY finicky, I had to make very fine adjustments sliding the chimney to the right to get the sensor between the 1/0 switching point to reliably get filament detected. I also needed to back the idler tensioning screw out much farther than was described in the initial directions to get detection reliable, and unless I wanted to jam my 1.5mm allen wrench between the extruder gears (potentially dulling them), I was not able to get the IR sensor to actuate at all with the wrench, just with the filament piece. In any case, I got it working, and then it worked as expected and I got layer height calibrated as I am used to, but it took way longer than it probably should have - this issue is a known, described one in other instructions, but its omission in the main list lead me astray in the very first calibration steps.
So my proposal? Add the IR sensor calibration step to the preflight check of the MK3S/MMU2S upgrade instructions. Would save you having to pull out partly loaded filament from the bowden, removing the bowden itself, and can ensure that a properly assembled upgrade doesn't immediately fail and softlock in the preliminary calibration steps with almost no feedback.
RE: Please include IR sensor adjustment as a regular assembly step for the MK3S/MMU2S kits
Yeah the IR sensor seems to be one of the two key issues for the MMU.
I'd like to see them go a step further and have us stop after reassembling the extruder and go through calibrations and test prints. That would probably make the process smoother for many rather than fighting potential extruder and MMU issues at the same time.
RE: Please include IR sensor adjustment as a regular assembly step for the MK3S/MMU2S kits
That is what I did. Well, I built everything fully, but before connecting and running through the MMU2 I went straight in and made sure it worked. Then I connected the MMU2 and printed a single color through it, and it works. Now I am having issues with the wallet. I have tried a few types of wallets and rewinding spool holders, but they have all failed. I am printing ones that are airtight, so I can use my water soluble support material without fear, so I cannot use the extremely open and exposed to the air one that Prusa provided.
RE: Please include IR sensor adjustment as a regular assembly step for the MK3S/MMU2S kits
Hi,
thanks for the feedback. The calibration part was always part of the Handbook, not the assembly itself and I dedicated a special step warning about the necessity of calibrating the IR-sensor.
However, it seems not all users open the Handbook, so I will extend the assembly with extra steps. On the other hand, it might confuse other users reading the Handbook, as the procedures will be described there again.
RE: Please include IR sensor adjustment as a regular assembly step for the MK3S/MMU2S kits
The problem is, that it is not said that one needs to do a selftest. Everything can be ok with the sensor on the display in the support section, correct 0 and 1 detection. But that doesn´t mean that the IR sensor will pass the selftest. I fiddeled around with material not loading and strange behaviour (loading filament 256...) for 3 days, cause I thought the sensor calibration is ok. The MMUS was leading me to the wrong path the hole time with telling me the FINDA didn´t work correctly (showing 1 at no loaded filament time by time),
I had two chats in two days about the potential problems causing this behaviour. In the second chat the guy told me it might be IR sensor related and I should follow the calibration in the handbook. This was still misleading, cause he never told me to perform a selftest. After reading about it in the forum, I performed the selftest and it failed (remember, Sensor info told me everything is correct). Some trimming on the door and slightly changing position and five selftests later I passed it.
Right now I´m printing PETG with a 0.2 mm nozzle without major issues.
So please write in the handbook: "You have to perform the selftest"
Cheers
RE: Please include IR sensor adjustment as a regular assembly step for the MK3S/MMU2S kits
I did actually use the handbook's guide ultimately, but the feedback from the printer/MMU is not detailed enough to point to it as a potential solution. The feedback you get in running the calibration wizard is the same as a normal load or unload error on the MMU, who's troubleshooting steps don't include IR sensor calibration because they assume that has already been figured out and the unit is otherwise working.
Looking through the handbook again, though, I must concede that it is officially part of the Quick Start. I think there's a couple reasons why it's often overlooked:
The quick start guide is quite long (for a quick start) and begins with some of the same steps as the preflight check, so it's easy to assume at a glance that it's duplicate material
Other parts that require fine alignment were mentioned as potentially difficult to get right in the assembly steps (like gear and filament path alignment), so the sensor potentially being misaligned doesn't really register as a potential assembly issue
In previous kit assemblies (the MK3 kit is going to be a common experience for a lot of MMU2S builders), once you get to the first layer calibration step, you're basically done with any physical adjustment, so it's easy to assume it's some sort of software or significant hardware issue if there's a failure at this point.
That said, I think without revising the handbook there are a couple potentially worthwhile additions that would clear it up and catch the issue before you get into a softlock in the firmware with it trying to load/unload a filament with bad sensor data:
The first mentioned one, adding an adjustment step to the preflight check
You could also add a mention of potential realignment or alignment issues to the final assembly steps of attaching the IR chimney to the extruder body steps
And something I just thought of, how about adding a check to the MMU2S calibration wizard? There is a section of the self test that checks sensor communication, why not add a step where it asks you if filament is loaded with a prompt, checks the sensor data, then unloads/loads a small amount of filament and checks again? I know this could involve the removal of the bowden tube to check it comprehensively, a check like this definitely would have caught the sensor issue I ran into my build, and a simplified version of it could just be reading the sensor and asking if filament is loaded (at this point it would be assumed that it isn't, but as a confirmation). With the single query you could get at least one state of the IR sensor checked without removing the bowden or actually loading any filament through the MMU or extruder.