Ok, so I got my new hot end in, everything works great there, now I'm trying to get my AO-100 the rest of the way working... but the bed either doesn't want to level or doesn't want to stick in some places. Also there's a grinding noise when the z tries to lift at the beginning of the print, which I think is related.
I've created a video, and uploaded to youtube... if you know what the grinding noise is or why I can't get the extrusion to stick to the bed in certain places, please let me know. Thanks.
Here's the details:
I leveled the bed as best as I can by hand (while everything was hot).
The z height seems to change every time I start a new print, so I have to constantly re-set the z-height screw.
I'm using heated glass with a fairly thick coating of hair spray across the whole thing... seems to stick well in most places, but there's a few it just refuses to stick.
The grinding noise is occurring as soon as the direction of travel changes. The printer firmware has two different manual move speeds- a manual movement speed and a homing speed. Your Z axis homing speed is fine (provided you have not reflashed the firmware), but if there's any binding, will cause that noise. How often are you lubricating your Z axis drive rod? We recommend lubricating the drive rod once a month, with either a petroleum-free silicone-based lubricant, or with white lithium grease. Apply the lubricant, drive the axis up and down while wiping off any excess. Alternatively, you can recenter your Z axis drive rods within the two couplers, and even turn down the Z axis homing speed/rate by changing a value in the firmware and reflashing.
Are you printing directly on the glass? You'll want to avoid that if at all possible unless you like buying borosilicate glass sheets.
The A0-10x stock Z axis endstop target is not the greatest. It drifting out of alignment with heating cycles is not your imagination. I solved that on the AO-TAZ linear rail modification by swapping in an actual micrometer head. Working within the confines of the stock piece. you may want to try dipping the threads of the z axis target in elmers white paper glue to form a light coat, then re-threading the piece. That should give it more friction but still allow you to adjust it.
You'll also want to look at printing and implementing one of the Dual z nut X end designs. WIth just the one Z nut per side, you do end up with a bit of Z axis hysteresis motion that can cause inconsistent layer heights from print to print, which is magnified on the first layer due to the Z endstip movement.
The grinding noise you hear may be normal starting to turn noises, or it may be one of the stock Z axis couplers failing. The stock coupler has a tendency to split at the bolt point and can allow the threaded rod to spin. There is a reinforced piece somewhere in the download.lulzbot.com archive called the "beefy coupler" that fixes that particular issue.