Yes, leveling the bed can be confusing. At first it seems like a juggling act but there are some hacks. I have a TAZ 5. Can’t afford auto-leveling so what I am giving you is really basic.
One of the first things I did was to put a white mark on the Z offset nob. Now when I turn it I know how many turns I have made exactly and there is an equality for the number of turns vs. the offset. Think of it as a jar lid. Counter clockwise raises the lid -and the leveling screws. Clockwise lowers the lid. The more you turn the Z offset nob counterclockwise the higher the extruder head will stop away from the bed. If the leveling screws are too tight you want to raise them so you will have to raise the X axis by turning the knob in order to give you room to raise the bed under the nozzle.
Here is another hack for leveling the X axis. I know not everyone has a miter saw (had one handy) but you probably know someone who does. I cut a 3/8 inch piece of plywood (had one handy) about 3 inches long and 50.6mm wide. Experiment for what works for you. The manual shows that you should use the metal ruler to measure the x axis on either side of the print bed beginning from the aluminum. I think this is “a pain in the tookus.” Remember HS when in science class they taught you to use a ruler and everyone had a different idea? It was never consistent. Placing the “block” on the aluminum at the back end and lowering the X axis by manually turning the threaded rods will give you a consistent height for the x axis every time. No bending over and going “Humm, is this right? Well maybe.” Duh!
Now for the bed leveling screws. I have over tightened and stripped the aluminum leading to replacing the aluminum bed. You could sauder a hex nut to the back of the aluminum bed but that might eventually break. Orrrr, just tighten the bed leveling screws down till they are snug and given that the x axis is level go on to the next step.
First I home when the bed is warm. Expansion. Also paper will burn at Fahrenheit 351. (Never read the book) That is 233 C. You don’t need your bed or your nozzle that warm when you level. That said, “Home All.” Watch to see if the nozzle forces the bed down. You don’t want that. Note that if your nozzle forces the bed down you can fix that by turning the Z offset nob counter clockwise. Do it one turn then “home all.” Make sure the bed is not forced down.
This is why I put a white mark or “tick” on the nob. I can tell how many turns I make and get pretty precise. If the bed is not forced down - here is the fun trick- you can slip or try to slip a piece of paper under the nozzle or your can use a bent finger gauge (No paper, no fire). If you use a digital caliper, (you should have one because it really helps.) you will find that the thickness of a “folded piece of paper” is .18 mm. Trust me. Use your finger gauge and get .18 mm between your bed and n nozzle. It’s always reliable and it’s slippery where paper is rough. You will feel the difference but if the bed is not forced down when you slip the gauge under the nozzle you’re golden. Business card stock varies in thickness (from .27 to .35mm) so, in my belief, it’s unreliable.
Now for the bed screws and springs. Yep! I note the same thing. One or more corners will seem to be screwed down tighter than others, or the bed corner is higher on one side than another. It’s called spring tension governed by the spring constant and I personally think it varies slightly from one spring to another. Unlevel bed corners catch on threads and stick. I have to get an order of springs in one package and replace all of them to check but this has been a bother to me for a long time. …and yeah I have replaced my springs before. Same problem.
Another problem is that the bed corner gets caught on the “inverted” screw (mentioned above) and to level you have to push the bed corner down. Sometimes it will pop and the corner will level out or the corner will be visually unlevel. You will have to "dink’ with it by raising the Z offset nob then re-leveling. The point is to give yourself room to raise the bed levelers. That is to say if the distance between the bed and the nozzle is too tight raise the Z offset by a counter clockwise turn, check the space between the bed and the nozzle with your paper or finger gauge and if you have to because the bed is pushed down, repeat until the (Here is the trick with the leveling screws being too tight.) nozzle is raised sufficiently so as to ease the turning of the leveling screws and all four corners are even with the finger gauge at .18 mm between the bed and the nozzle. One other thing, I used a longer inverted “stabilizing” screw on the bed corner. I just have a little more flexibility when adjusting the bed height. I call them “post screws” because they look like posts and I think they should be smooth at a level above the aluminum because the threads serve no purpose and the levelers need to slide so they don’t get caught when leveling the bed with the leveling screw.
One final thing before I confuse you more. There is an exact number of turns of the Allen wrench per fraction of a mm you raise the bed corner. Sorry, I have forgotten it for the moment but it will help you when you realize that you can divide precisely a complete turn and equate that with an increase in bed height. One turn equals x mm of height. It’s important if you are making molds and can get within .04 or in some cases .02 mm. Takes a math nerd.
