I have a Wanhao i3 plus clone, monoprice maker plus. At least, that is what I was told 
. Anyhoo, I was printing parts out with only small issues, but still usable, just messy. So, I read a bunch of stuff and decided to upgrade my printer with a few basic necessities. After putting it all back together, the bed will no longer level.
Problem: With the glass on, I can get three corners to level but the final one shows a huge gap. This leads me to believe that the nozzle has some software offsets that prevent it from properly leveling. However, I have no idea how to access those or whether this is the true culprit. The final corner is pushed down by the pressure of the three other corners and makes the final nut so loose that I am unable to align it.
Upgrades:
Micro Swiss all metal conversion kit
Sturdy aluminium base plate (perfectly level and flat, although I did have to flop the printer on it’s side to access the panel underneath so that I could remove the heating leads. But, everything seemed to have gone fine.)
Boroglass plate made for the printer with beveled corners (also, perfectly flat.)
Thermo sheet between the bed and glass.
PS: The standard build plate is also perfectly level and flat. No bending or bowing.
Upgrade to the firmware to the ADVi3app (I had to remove the front plate which means I had to remove the y bars. But they seem to be kosher as well. Well aligned.
Enough words from me. Commence 
Update, I tried to level the bed without the glass, and it levels in the corners as expected but the nozzle is too close in the center. Okay, not bad huh? Well, I put the glass on top and it now teeter totters where the fulcrum lies across the diagonal that crosses position 1, 5 and 2 (center, NE and SW corners) and rocks back and forth between corners 3 and 4 (NW and SE corners). The bed is no longer flat and bows but the support plate below is perfectly rigid and flat as it was after install (aftermarket support plate. Solid aluminium CnC cut to perfection). So, the build plate requires being bowed across the diagonal that passes through 1,5 and 2 in order to be aligned with the default print head locations (assuming, with offsets programmed in). This seems odd to me that the print head is lower on both the 3 and 4 position than it is in the 1 and 2 positions. Both sets are opposite corners.
This leads me to believe, seeing as how the glass is perfectly flat and the bed is now warped to meet the expected corner heights that the extruder is set to, that two diagonal corners are higher by about 2mm and the other two are perfect. Or, two are higher by 1mm and the other two are lower by 1mm. Is there a way for me to check the extruder calibration information and change this on the fly to reach the proper heights instead of using the screws? It would be nice to use a perfectly flat and level surface(I use a level for every aspect of the printers alignment) to print on and use the software to compensate its own variation.
Any help would be appreciated.
This is not my video, but it shows off the same resulting problem.
Other than replacing the warped bed, an auto leveling system would be your best bet. If you can run Marlin firmware it makes it fairly easy, a genuine BLtouch would probably work here.
The problem is, the bed is not warped. The bed, the support below, and the glass are all perfectly level and flat. But, when I go to level the system, the head moves too close to two opposite corners, and farther away from the other opposite corners. If this was just 1mm, that would be fine, but the discrepancy is 2 to 3mm. So, I have to basically warp the bed by tightening two opposite corners to account for the heads position in those sections. Things print fine when I do this without the glass. But, it just doesn’t feel right knowing that the bed is perfectly flat and level yet the head does not meet the level bed… ahem… level.
Anyways, thank you for replying. I was looking into the BLTouch and already have Marlin firmware installed via ADVi3app. I just picked up the device and an extension kit.
I know this BTtouch will work, but why can I not get the bed level manually? Why are the two opposite corners so far off from the other two corners? Maybe one day I will find the reason.
Are you leveling manually or via software? my recommendation would be to have the printer home, then disable the steppers and manually move the printhead around the bed.
When you’re leveling currently, can you tell if the Z is raising and lowering at certain points?
