z axis calibration failure
I just built a MK4S. I am going through the axis calibrations. The X and Y passed but the Z fails. I looked for what to check and everything that I can see looks fine. One time it passed and all was well until I went to print my first item. The key chain that was recommended. Then the print head went down and dug into my print plate. I got an error about the filament jamming. So I did that a couple of times and it did the same thing. So I did some more checking and decided to recalibrate all three axis. Again the X-Y passed. The load sensor passed. I barely had to touch it for it to register. I mean barely. Then it went through the Z check and it failed after it passed the day before. Have not touched anything. I checked the nozzle and it seems located right. I even checked to see if the tape on the sensor was damaged and even though the instructions says it should be white (mine is black) there appears to be no damage. I loosed the bolts on the X-carriage in hopes those nuts would align. No go. Since it worked once but not now I am really confused and not sure what to check. Here are some pictures.
RE: z axis calibration failure
I might add. When I first turned on the printer and went through the checks I got to the load test. It passed but when it went to the Z axis test it screamed at me saying the load sensor was off. Check the bolts. So when I did I noticed they were fairly tight. So I loosened them. I then just snugged them down instead of tightening them. That got me past that point but still had issues with the z-axis failure. I did see the article on checking the nozzle and oriented it like it was on the picture in the article and checked the depth as you can see in the pictures. I noticed the left z rod seemed stiffer when moving it so I loosened the bolts holding in the nut and moved the X axis bar up and down. Then reset the nut but snugging the bolts. After that the test passed until I tried to print since everything was supposedly checked out. That is when I found out that the z axis is again not passing.
RE: z axis calibration failure
Have you sorted it out yet? I had the same problem with my build this weekend. Nozzle driven straight into the built plate, it's kinda of ruined. First it wouldn't pass Z calibration, and I notice that the left Z motor/carriage was binding, I managed to get it to move by helping to turn the screw a little with my hands, I also put some grease on the trapezoid screws, Why the manual doesn't tell you to do this is beyond my understanding, it's clearly a metal to metal slidy part.. In any case, I eventually got it to pass, but there were many other ghosts in the machine. The load sensor seemed off somehow, it would hoover around 1000 at idle (or smoething similar, it was not near 0 atleast...) I remembered I had to put's some twisting force on the nozzle to fit heater block, do to the hotend cables, which i think might have caused the load sensor to be off. I loosed the hotend screws and let the nozzle be at a slight angle, kind of where it "wants" to sit rather than forcing it straight. Recalibrated the load sensor and it checks out, idling near 0. I also noticed one of the bearings in the x carriage had popped out of it's pocket so that also might have caused me some problems, also fixed. I also disabled the clog setting as it would activate when trying the 14minute benchy on the usbcard. I still haven't been able to print that one, it fails quite early, do to crashing into the part, it looks like its overextruding but I'm not sure. After failing a couple of times I printed a benchie sliced in prusaslicer, and thatone came out perfectly, it was obviously a slower print, 37 minutes but it was pretty much perfect. So I thought everything was all good, printed some other parts. Then again the 14 minute benchy (failed) decided to go for a first layer test, and that came out horrible, I then noticed the left Z motor was slightly missaligned, it was about one mm lower than the right, and has made some light drag marks on the other (still good) side of the PEI sheet. So back to realigning everything mostly focused on the Z screws this time as everything else sounds smooth in motion.
Recalibrate, and for the moment it seems to be good, I'm gonna print some parts tonight and keep an eye on the Z alignment..
So try to realign the Z screws, I had to shift(horizontal) the left motor sligthly, there's isn't much wiggle room but enough to make a difference. Also remove the trapezoid nuts from the carriage and move them manually along the screws to check if there are any binding spots, they should spin very easily. But before all of this, GREASE THE SCREWS.....
RE: z axis calibration failure
Another thing to add is to make sure the Z/X carriage is parrallell to the printbed when calibrating after realigning the screws/trapezoid nut. This was probably also one of the reasons it would jam on me on my first calibration attempt. Imo they should have you start the whole thing with the carriage at the top to assure that it's parrallell... and grease the screws....
RE: z axis calibration failure
Yes, I was able to get things working. I did a couple of things. I loosened the screws in the heat sink for the load sensor. I had tightened them when snug is all you want. I also noticed the left z axis motor seemed to bind more than the left. I had trouble getting everything to go together for that side. So I loosened the nut and let it align itself. That worked once and then the same issue. Still the LH side was tighter than the right. So I took the brackets off the top, moved the X axis up and hung it by its hanger tool and took off the nuts on both sides. I noticed there was some flash inside the nuts so I scraped that off with a knife. I then took a good look at the alignment and noticed the screw rods were not centered. LH side was much worse than the RH side. I moved the X axis up and down and noticed the LH side had a bbbbbrrrrppp as it moved up and down. So the screw rod was touching. I readjusted the screw rods on both sides. This time making sure they were centered. Again I moved the X axis up and down and made sure no sound was being made. Good to go. For the fun of it while I had the nuts off the screw rods I checked to make sure I did not cross thread them. Nope. I then took the nut that was on the LH side and put it on the RH side. And the RH on the LH. Well no matter which nut I put on the LH side it was always slightly and I mean slightly tighter than the RH side. So that tells me the LH threaded rod is ever so slightly larger in diameter. I then proceeded to put the top brackets on. This time they both went on with absolutely no issues. Once I knew the thing as aligned better I then did the checks and it passed. No issues with anything. It has been working every since just like it is supposed too. So I would suggest you do the same and check your alignments. As for why the one motor is lower than the other, you did put the rubber pads under each motor didn't you? Anyway, this is what I did and it fixed my issues.
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Good to hear! My machine has been working well since, there is still some buzzing when i run the Z manually. All parts are correctly installed, the problem is that the motor itself is mispositioned horizontally, the distance between the screw rod and Z bearing rod is about 9.7mm at the bottom and 10.2mm just under the X/Z carriage (when it's at the top) this is after I repositioned it. I so it's still 0.5mm off. It's also visible because the screw moves inwards a little over 1mm when the carriage is at the bottom. I'm gonna try to push it further but I doubt it'll go, I guess I could reprint the left Z motor bracket.. The Right side is also abit off now I'll try to fix that too...
RE: z axis calibration failure
I dropped the left motor and tried to melt the screwholes slightly towards the right, mildly succesful, distance between rod and screw is now 9.9mm.. I'm guessing it's specced to be 10mm I didn't meassure it before I moved them the first time, but probably closer to 9 than 9.5mm