Ender 3 unknown (maybe bed leveling) issue

Question

I halfway feel like I walked into a landmine, neighbor's kid saved up and bought an Ender 3 base model printer. Just before it was given to me he installed a BL touch I bought him in exchange for him printing some parts I was modeling and so our story starts...don't think I can go into my full sob story so I'm going try and cut to the chase but I have little knowledge of how this is put together and coming in in the middle and backpaddling whether is was put together correctly.

As a 3D modeler I attempted to print a demo file or two in preparation to print a case for a raspberry pi camera I've been working on during COVID. At some point during the print while I wasn't around the bed flew off, and there was an inch of plastic melted around the head. Long story short I spent the last week finding, buying and replacing the whole hot end assembly as it was cheaper then repairing it. So now I believe I'm back to square one.

While watching something print, I noticed the PLA wasn't getting bunched off on one part of the print so I stopped it before a repeat of earlier in the month happened. While sitting on the floor I began to notice the right side of the bar where the hot end/nozzle attaches is about 1 cm or so higher then the right. As I have no frame of reference I'm hoping someone can confirm whether that should be the case. Raising the Z to the top and measuring to that cross bar I don't know that it's the bed but I don't have a small enough level to put on the bed.

I'm seeing if I print something like a calibration cube it's printing OK, but if I go for something wider like 3D Benchy or my camera case the filament only touches on one part of the bed. This is occurring on both the original bed and the glass bed I installed and readjusted the Z for.

Sorry...Hope that's not TMI, there's a lot going on. Also I'm using a spool of Hatchbox PLA if that matters and the new hot end is a Creality one from Microcenter as I didn't trust what was on Amazon to be 'authentic'.

Answer 1

Non-square gantry is a common problem with the Ender 3. You should be able to compensate by adjusting the bed leveling screws so that the nozzle at Z=0 is touching the bed at each of the four adjustment points. This will leave some skew, which you may or may not care about. But the right thing to do is leveling the gantry.

Both sides' Z carriages have some play in how the gantry mounts to them - the holes are larger than the machine screws that go through them - so after loosening the screws you can make adjustments. The screws on the side with the Z motor are hidden between the carriage and Z axis extrusion it rolls on, so to adjust it you need to roll the whole assembly off the top of the printer (with the cross beam at the top removed). Since you can't tighten it in-place, you just have to do your best to get it straight before putting it back on. The unpowered side, however, has screws that are reachable with the whole assembly in place, so you can square the gantry with the Z extrusions before tightening them.

Keep in mind that the whole Z axis system is severely over-constrained, with 6 wheels where 3 should suffice to constrain it. People have a lot of different ideas about how you should deal with this, and I'm still not sure what's best, but I think you want to get each of the V-roller sets tight (using the eccentric nuts to adjust the inner wheels) before leveling and tightening down the gantry. Otherwise the wheels may have uneven tension, causing the assembly to want to twist.