There seems to be a lot of confusion and different techniques out there on how to "Level" a print bed. Hopefully this article will explain a few things and will be broken up in different sections. 

First, lets talk about the term leveling. The term is misused often, and confuses some into thinking the bed should be actually level. Some have gone as far as setting a bubble level on the machine and using that. The correct term is actually Tramming. 

Tramming is the act of making 2 parts of a machine true to each other. in this case, we want the nozzle to be the exact same set distance from the print surface to the tip of the nozzle. Right now, I want you to STOP thinking about adhesion, and first layers, and all the things that happen when we are actually putting the plastic down - that comes later. Tramming has nothing to do with that, at least not directly. All we need to be concerned about with tramming is that the nozzle, no matter its position along the x and y axis is exactly the same height to the current z height. 

Axises: if you are confused about x, y, and z axis and what Im referring to here, read on, otherwise skip this section. The X, Y and Z axis indicate directions in which the printer moves. Depending on the type of printer you have, it may be the bed moves front to back to achieve one direction, in the case of most Ender 3 series, Cr- series, or the bed may move up and down, in the case of a machine like a ender 5 plus, ender 6, Sermoon D1, and so on. No matter which type you have, the X Y and Z indications are standard. Y is front and  back, X is left and right and Z is up and down, as you are looking at your machine head on. 

When we are thinking along the terms of tramming, you must think about the left to right as the X plane and the front to back as the Y plane. the object is to make the distance from where the nozzle is right now, the same everywhere, no matter the z height. if the nozzle was 30 millimeters off the bed in the middle, it should be exactly the same in all the corners, and all the points along X and Y in between. it should be a constant. another example is if the nozzle is just 1 millimeter off the bed in the front left corner, you should be able to move it anywhere around along the X and Y planes and as long as the Z height does not change, it should be exactly the same everywhere.

Now to how I handle leveling. You should already have the Z offset (the height of the nozzle when its ready to print) set up. you should bring the printer to the center of your bed - it will be the truest point in the bed no matter how off your bed is. Bring the nozzle to the z offset. usually this can be done by homing the printer, but in the case of a ender 3 without a BL/CR touch system, it will home in the corner. disable the motors, and slowly, carefully move it to the center of the bed. If its contacting the surface, we need to adjust that by using the side limit switch. We will cover this in another guide.

The first thing you want to make sure of is you have the upgraded bed springs on your machine, or the silicone mounts. They shoud be yellow/orange, or if you have another brand, maybe blue. if you have the silver springs, they will work, but they do not handle staying put well. If you do not have the upgraded springs, please see my affiliate links section to get the kit.

Preheat your bed to 60 degees, and home the printer.

Next, turn all 4 leveling wheels all the way tight. this will load the springs to 100 percent load. Then loosen each knob about 1 turn. By doing this we are setting up the bed to be pretty close to the same in both the X and the Y direction. After backing the wheels off by about a turn, you now have room to adjust both ways, but the springs are at about 80 percent load. This tension will help keep the wheels from backing off over time and changing the level of the bed. 

The next part depends on what printer setup you have. Some will have a manual leveling assist in the menus where it will move the printer head over each of the wheels, some will require you to disable the motors and move the head manually. 

if your print head is in the center, it should be very close to the bed surface but not touching. Dont worry about the height just yet, just make sure its not contacting the bed.

Now its time to make laps around the bed, adjusting knobs. Each knob we adjust will affect the other 3 corners, and usually the one diagonal from it the most. pick a corner to start in, and either use your menu under manual leveling to bring the head to that corner, or if you are using a ender 3, with the motors disabled, bring the nozzle directly over a leveling wheel.

What you use as your guide is completely up to you - some like shims, some like paper, it does not matter as long as you are able to tell that the distance is the same. In the case of a shim it either fits or it does not, and with paper, you have to develop a feel for the scratch/resistance. For this guide I am going to assume paper. Slide the paper under the nozzle in the first corner. If it doesnt fit under, tighten the bed wheel  to pull the bed down away from the nozzle until it does. It should move freely. Then loosen the wheel to raise the bed and close the distance between the bed and the nozzle, until you feel enough resistance on the paper to make it scratch when you move it back and forth. Try to move it back and forth a few times to get a feel for how it moves, you need to remember that feeling for each corner. you dont want it so tight that it rips a hole, and you dont want it so loose you can move it very freely- there should be a bit of resistance. If your printer is on, sometimes you will hear a buzz as you move the paper and the fans motor resonates - I like this as a auditory guide as well as feeling the scratch. Once you are satisfied you are scratching well and know the feeling of it, move to the next corner.

You will go to all 4 corners in this fashion and will likely be making large adjustments to the wheels this first pass around. ***IMPORTANT TIP*** do NOT rest your hand on the bed while sliding the paper, your hands should be not touching anything but the paper. Likewise try not to hold onto the wheel while testing the paper sliding - use a fingertip on the side of the wheel to move it. The red aluminum wheels are a nice addition for this as they are easier to turn this way. (link in affiliates page) The reason is, any influence on the bed will change the spring tension and can alter the actual height when you remove your hand. 

Once you have gone to all 4 corners, go back to the corner you started with. The first pass was the rough pass where we set the height in large wheel movements. each subsequent pass around the bed will be far less drastic movements - now we are going to fine tune the changes each wheel has on each other. again slide the paper under the nozzle. if you have the manual assist, pressing the corner you are on will raise and lower it with enough time to slide the paper under. If you have no manual assist in your software, and you are doing this with disabled motors, VERY lightly press down on that corner of the bed and slip the paper in - the spring tension should bring it right back to where it was. adjust as needed until you feel the correct amount of friction. It will take very slight movements. too tight? tighten the wheel. Too loose? loosen the wheel. easy way to remember it is my paper is tight, I need to tighten the wheel, or my paper is loose, I need to loosen the wheel. At this stage the movements will be super slight, so very small turns should do it. If the paper feels right without any adjustment, leave it and move to the next corner.

The final pass - once you are able to get around the four corners without needing to adjust it, you are done. the bed is now trammed to the nozzle. Aside from a warped bed, you should be able to move the nozzle anywhere over the print surface and the paper will have that same resistance.

Now that that part is done, we need to set a Z-offset. The Z-offset is how close is your nozzle to the surface when printing. This DOES affect adhesion, texture, etc.

 If you have a BL Touch/CR-touch, there should be menu options to set this height. machines without this setting, you will home the machine and use a menu option usually to adjust the z height. place your paper under the nozzle and adjust using your menus to raise and lower the z-height, until the paper has that same resistance. There are many different ways the z-offset is set -  and each machine is a bit different. If you cant figure this part out, reach out to me with what machine you have and I will try to assist you. 

LIVE Z-OFFSET - this is the best way to fine tune the z-offset. load a calibration cube into your slicer and use the scaling tool to make it about 75 percent of your bed. For ender 3 users, about 175 mm will work. Make sure the uniform scaling is checked off and scale it up. Dont worry - we arent going to print the whole thing. Slice it and put it on a SD card. 

In most software on the printer, in the print menus, there is a tune option you can use while printing. Start the print of the giant cube. Let it lay out the border, and as long as that is sticking ok, wait until its laying down the first diagonal layer. If its too low or too high during the skirt, or border of the cube, use the babystep Z/Z offset compensation/Z height - whatever its called in your menu to fine tune until its a good line sticking, and looks normal. As it begins to lay down that first infilled diagonal layer, use that long time to raise or lower your z-offset as needed. if the plastic looks rough, you are too close, if there are gaps between the lines, you are too far away. Positive numbers raises the nozzle from the bed, negative numbers brings it closer to the bed. You want to see lines that are well connected, and no gaps, but not rough blotchy plastic. once you get this right you should see a nice sheet of plastic being laid down. Most machines will save this Z offset, but it doesnt hurt to write it down. 

Once you are satisfied, abort the print, and for good measure use store settings in your menus to make sure its saved. 

Remember Leveling is tramming - and tramming is ONLY talking about making the nozzle and the X/Y planes parallel. Nothing to do with how close it is when printing - that is Z offset.

hope this helps you, and if needed reach out for any questions on messenger, I'll always try to help.

Jim, That3dPrinterDude.