Nextruder issue, and Homing?
This may be a double post, I tried posting it at like 1 am last night, and when I came back this morning, I received a 404 and couldn't find it, so If it is a double post, i'll delete, and I apologize. But, anyways! I finished assembling my Prusa Core One + last evening, I used the Prusa web app to get the correct HZ with the belts, everything calibrated, except the homing calibration said it was unable to be completed, but then I noticed that the calibration had a green check mark off, so I'm unsure if this is a software issue, and it actually calibrated? or if it's not actually calibrated.
Secondly, and this is more of an issue, and i'm not quite sure what the deal is. The nextruder is making that terrible grinding noise, I went through the entire nextruder assembly again and double checked everything (I didn't take it all apart and rebuilt it, just double checked everything with each step and what I could see with the cover off). But as you can see the nextruder starts to spin, and then it seems like it catches and just grinds and bumps back and forth. Any help is beyond appreciated, seriously beyond appreciated.
RE: Nextruder issue, and Homing?
1. Homing calibration failed because the gantry is not square. You probably skewed it when you tensioned the belts. You must turn both screws by the same amount. Completely loosen the belts, then manually bend the gantry until it is square with the frame, use this as a guide: Adjusting belt tension read it carefully. Then turn each screw the same amount alternating between screws until the belts come under tension. Then only turn each screw 1/4 or 1/8th of a turn, always in the same direction and by the same amount.
2. If I were to guess, you don't have the nozzle fully inserted into the heatsink that or the tensioning screws on the idler are too tight. Make sure it is inserted fully like this
RE: Nextruder issue, and Homing?
Thanks a ton! I'll try that shortly and get back to you! Definitely appreciate the help!
RE: Nextruder issue, and Homing?
Ahg, so, i'm so lost at this point. The PG ring and the gears spin when off of the motor, the motor spins freely with nothing on it. The space is on the motor spindle, but when I attach them, it locks up. I referenced my MK4S nextruder, and i can stick my finger in and spin that one pretty freely, I can't do that on this Core One assembly. My assumption was that it must be getting tweaked on tightening and not be straight, but I've tried a ton of different tightening strengths and I followed the correct tightening order, but nothing. I went over the assembly again and everything seems perfect. Also, the motor is pretty lose until I tighten it with the grub screw and the other 3 screws that attach the entire assembly, I'm assuming that is supposed to be that way? 
On a positive note, I did get it homed correctly though! Thank you!
RE: Nextruder issue, and Homing?
I just chatted with support, and they thought maybe the motor didn't have enough power to spin, but on my MK4s I can spin the nextruder gear from the opening when the latch is open, I can't do that on the core one so that doesnt seem like the issue, and then my other thought would be potentially its a bad PG ring that just isn't QUITE right when the shaft is going through the gear.
RE: Nextruder issue, and Homing?
Do you have the PG-assembly-adapter? I would at this point disassemble the PG gears and use the adapter to properly reseat them.
RE: Nextruder issue, and Homing?
Do you have the PG-assembly-adapter? I would at this point disassemble the PG gears and use the adapter to properly reseat them. Also check for any debris between the main plate and the main gear.
RE: Nextruder issue, and Homing?
Yes, I disassembled entirely and then tried reseating. Prusa is sending me a new motor and a new PG plate, but i'm still stumped, because I just don't understand I don't think its the motor because it spins and i should still be able to spin it with it seated, it has to be some sort of alignment issue or an issue with how the PG adapter was machined. I'll probably fully pull out the nextruder over the weekend and try putting it together and getting it to spin outside of the machine. I really appreciate the help!
RE: Nextruder issue, and Homing?
the motor is pretty lose until I tighten it with the grub screw and the other 3 screws that attach the entire assembly, I'm assuming that is supposed to be that way?
That long grub screw (Prusa calls it the "socket set screw" in the instruction) is inserted pretty deeply in your build. It sticks out a bit further in mine and on the photo in the assembly guide. Did you tighten that screw only gently, as suggested by the instructions?
RE: Nextruder issue, and Homing?
I'm guessing, but I think the gear assembly tool prevents you from being off a tooth when the parts get engaged. That would cause high friction. I suspect one could assemble the gears without the tool, being very careful to feel the backlash on each gear after dropping the assembly on the motor. The forces need to be balanced so each side of the motor shaft is applying the same force to each gear. Hopefully I've described this well enough that some sensitive wiggling will determine if the gears are correct. Use the tool but don't 100% trust the tool if the result doesn't seem right. BTW, I found that the assembly didn't rotate all that freely with the tool in place if the outer gear plate was fixed because (I think) you're back-driving the motor. If the plate is allowed to move, it will spin with almost no force.