When you print your 3D parts, your first layer is crucial.  They act like the foundation of your 3D parts and if anything happens, your 3D prints are probably going to fail. 

If your 3D printer has auto bed leveling features, you are lucky.  You don't need to worry about this.  Just make sure you conduct auto bed leveling between prints.

However, if your 3D printer doesn't have auto bed leveling, I will provide information about how to complete manual bed leveling, and how to check if your bed is leveled.

What you need for manual print bed leveling.

The process

1. Clean the nozzle first.  Any residual plastic on the nozzle will induce errors when you try to create an accurate nozzle-to-bed gap.  Dry cotton cloth, pliers, and brass brush are okay to use to remove those residues before you head up your print bed and start bed leveling.  If there are any residuals inside the nozzle, heat the nozzle to printing temperature and wait for the residue to ooze out before removing them.  Of cause, be aware of the heat, pliers are used when the nozzle is heated, wait for the nozzle to cool down if you want to use your cotton cloth and brass brush, and WEAR YOUR HEAT RESISTANT GLOVES!

2. Clean the build surface.  Clean it also ensure the accuracy of the nozzle-to-bed gap.

   • For glass build surface, a razor blade or spade is used to remove residue from the plate

   • For PEI coating build a surface, don't use a spade or blade, just try to remove the residue using your hands.  PEI plate is known for easy part removal and there shouldn't be large residue on the plate.

   • Do clean it with isopropyl alcohol after removing residual from your plate.
     
     

3. Reset your build plate screw position.  Screw the 4 rotating knobs to the tightest so that the build plate is the farthest from the nozzle.  It helps eliminate any dispositioning during previous print or large movements that lead to the plate not leveling (like moving the printer to other places).

4. Position the printhead.  Get the nozzle close to the print bed and let the printer know it is at the position (0, 0, 0) on the X, Y, and Z axis.  The 0 on the Z axis is crucial as it dictates the success of first-layer printing.

5. Free your print head on the X and Y axis / order your printhead to move to the 4 corners of your build plate.  For some old 3D printers you may need to disable the stepper motors so that you can move freely on the X and Y axis.  But most new printers can move it for you to the 4 corners of the build plate.  A.K.A You don't need to disable your stepper motors, just order the printhead to move into the 4 corners and do the bed leveling.

6. Measure and adjust the rotating knobs.  It is when the paper / thermal paper comes in handy.  Position your print head nozzle to the 4 corners of your build plate, and make sure the nozzle is just touching the paper / thermal paper which is placed on top of the build plate.  This ensures the creation of the nozzle-to-plate gap and ensures your print won't under-extrude (nozzle too far from the plate) or over-extrude (nozzle too close to the plate).  Sometimes it is normal to see that you can't completely level all the points as the hot plate may warp.  Just make sure the 4 corners are just touching the print bed and it is okay.

   • Manufautre mostly compacts this with the use of BR / CR touch.  BR touch or CR touch is introduced and creates a 3D mesh of your print bed.  The nozzle will then follow the curvature of the print bed during the print, hence solving the issue.

   • These functions are mostly included in newer printers, in which auto bed leveling is included.

7. Move your nozzle to the middle of the plate and set your Z-offset.  After calibrating the 4 corners, move your nozzle to the middle and see if the resistance you feel on the paper / thermal paper is just the same as the 4 corners.  If not, change your Z-offset accordingly to fine-tune it.

8. Start your first layer print test.  Use any print you want, and stop when the first layer is done printing.  Observe any artifact that indicates an unlevel print bed and change your setting accordingly.  (like turning rotating knobs and changing Z-offsets).

Video for better understanding

First layer observation