Tuesday, March 22, 2022

Calibrate Ender 3 V2 with Klipper

Calibrate a Ender 3 V2 running Klipper1 with the following tests.

Calibrate movement

Run the following tests to ensure the hotend and bed are moving correctly and can reach all points of the bed.

Check endstops

This ensures the endstops are connected and configured correctly.

  1. Check that all endstops are open

    QUERY_ENDSTOP

    All endstops should be in the open state

    # x:open y:open z:open

  2. Push the x endstop and query

    QUERY_ENDSTOP

    The x endstop should be in the TRIGGERED state

    # x:TRIGGERED y:open z:open

    Repeat for the y and z endstops

Check stepper motors

This ensure the motor pins are connected and configured correctly.

  1. Give the motors room to move back and forth by ensuring each axis can move in either direction freely

  2. Buzz the x stepper motor

    STEPPER_BUZZ stepper=stepper_x

    The hotend should repeatedly move from the left to the right.

  3. Buzz the y stepper motor

    STEPPER_BUZZ stepper=stepper_y

    The bed should repeatedly move to the front and back.

  4. Buzz the z stepper motor

    STEPPER_BUZZ stepper=stepper_z

    The hotend should repeatedly move up and down.

Check homing

This checks the nozzle can reach all four corners of the bed.

The bed is of size 235x235mm with corner coordinates of:

Cornerxy
Front left00
Front right2350
Back left0235
Back right235235

  1. Home all axis

    G28

  2. Go into absolute positioning mode2

    G90

  3. Move to the front left corner

    G1 X0 Y0 Z10 F3000

  4. Move to the front right corner

    G1 X235 Y0 Z10 F3000

  5. Move to the back left corner

    G1 X0 Y235 Z10 F3000

  6. Move to the back left corner

    G1 X235 Y235 Z10 F3000

Bed levelling

With a BLTouch3 probe installed, we can perform the following to ensure a level bed.

Configure BLTouch

Add the following to the printer.cfg4:

[bltouch]
sensor_pin: ^PB1
control_pin: PB0
x_offset: -42
y_offset: -10
z_offset: 0

[safe_z_home]
home_xy_position: 117.5, 117.5
z_hop: 10

x_offset, y_offset, z_offset are how far the BLTouch probe is from the nozzle. The z-offset will be adjusted later to ensure the nozzle is the perfect distance from the bed for a perfect first layer.

The above values are for the standard mount provided by BLTouch kit for the Ender 3 V2.

Adjust screws

Before we perform a bed mesh levelling, we should ensure our bed is as flat as possible by adjusting the screws under the bed. Klipper has automated tools for determining how much each screw needs to be adjusted5.

  1. Add the following to the printer.cfg to configure where each screw is located beneat the bed (screws on an Ender 3 V2 are offset by 32mm from the edges of the bed)

    [screws_tilt_adjust]
screw1: 74, 42
screw1_name: Front left
screw2: 245, 42
screw2_name: Front right
screw3: 245, 213
screw3_name: Back right
screw4: 74, 213
screw4_name: Back left
screw_thread: CW-M4
horizontal_move_z: 10

    The location for each screw is calculated as follows:

    Screwxy
    Front left0 + screw_x_offset - bltouch.x_offset0 + screw_y_offset - bltouch.y_offset
    Front right235 - screw_x_offset - bltouch.x_offset0 + screw_y_offset - bltouch.y_offset
    Back left0 + screw_x_offset - bltouch.x_offset235 - screw_y_offset - bltouch.y_offset
    Back right235 - screw_x_offset - bltouch.x_offset235 - screw_y_offset - bltouch.y_offset

    The above values are for the standard mount provided by BLTouch kit for the Ender 3 V2.

  2. Calculate how much each screw needs to be adjusted

    SCREWS_TILT_CALCULATE

    Each screw will be probed by the printer to produce a readout similar to the following where adjustments to each screw is displayed:

    # Front left (base) : x=74.0, y=42.0, z=-0.11500
# Front right : x=245.0, y=42.0, z=-0.10000 : adjust CCW 00:30
# Back right : x=245.0, y=213.0, z=-0.16500 : adjust CW 00:42
# Back left : x=74.0, y=213.0, z=-0.17000 : adjust CW 00:22

    The adjustments are based on a clock, where CW is clockwise and CCW is counter clock-wise. The amount of adjustment is in minutes. So for example, CCW 0:30 means to turn the screw 180 degrees counter clockwise.

  3. Repeat the above step until the adjustments are no more than 6 minutes each

Perform bed mesh levelling

We need to generate a height map for a series of points across the bed to cater for warped bed surfaces. Klipper has an auto bed levelling procedure to automate this6.

  1. Add the following to printer.cfg

    [bed_mesh]
speed: 120
horizontal_move_z: 10
mesh_min: 15, 15
mesh_max: 205, 205
probe_count: 5,5
algorithm: bicubic
fade_start: 1
fade_end: 10
fade_target: 0

    probe_count sets the size of the mesh, in this case 5 by 5, resulting in 25 points to be probed.

  2. Run the auto bed levelling procedure

    BED_MESH_CALIBRATE

  3. When complete, save the mesh

    SAVE_CONFIG

    The mesh will be saved to the printer.cfg like so:

    #*# [bed_mesh default]
#*# version = 1
#*# points =
#*# 	  -0.122500, -0.097500, -0.062500, -0.042500, 0.002500
#*# 	  -0.047500, -0.030000, 0.017500, 0.032500, 0.072500
#*# 	  -0.055000, -0.030000, 0.020000, 0.040000, 0.087500
#*# 	  -0.070000, -0.062500, -0.017500, 0.000000, 0.045000
#*# 	  -0.130000, -0.132500, -0.102500, -0.082500, -0.052500
#*# tension = 0.2
#*# min_x = 15.0
#*# algo = bicubic
#*# y_count = 5
#*# mesh_y_pps = 2
#*# min_y = 15.0
#*# x_count = 5
#*# max_y = 205.0
#*# mesh_x_pps = 2
#*# max_x = 205.0

Adjust the z_offset

This ensures the nozzle is the perfect distance from the bed for a perfect first layer.

  1. Find a piece of paper and place it under the nozzle. I have found a Post-it note7 to be a good thickness.

  2. Start the calibration

    PROBE_CALIBRATE

  3. Adjust the nozzle height until there is friction on the paper To go down:

    TESTZ Z=--

    To go up:

    TESTZ Z=++

  4. Once the nozzle is at the correct height, save the z_offset

    SAVE_CONFIG

    This will appear in the printer.cfg like so:

    #*# [bltouch]
#*# z_offset = 5.063

Run a calibration print

After going through the above configuration we can confirm everything by running a calibration print.

  1. Use SuperSlicer8 to generate the calibration G-code

    generate bed levelling G-code from SuperSlicer

    The content within the dialog describes what a successful print should look like.

  2. A successful print should look like the following

    generate bed levelling G-code from SuperSlicer

Calibrate temperate

This ensures the nozzle and bed heaters are able to keep the temperature stable9.

  1. Turn the part fan to 100% to simulate real cooling

    M106 S255

  2. Tune the extruder

    PID_CALIBRATE HEATER=extruder TARGET=200

    The TARGET should be close to the typical printing temperature for the filament. 200 is good for PLA.

  3. Save the config

    SAVE_CONFIG

    This will appear in the printer.cfg like so:

    #*# [extruder]
#*# control = pid
#*# pid_kp = 20.237
#*# pid_ki = 1.054
#*# pid_kd = 97.138

  4. Tune the heater bed

    PID_CALIBRATE HEATER=heater_bed TARGET=60

    The TARGET should be close to the typical printing temperature for the filament. 60 is good for PLA.

  5. Save the config

    SAVE_CONFIG

    This will appear in the printer.cfg like so:

    #*# [heater_bed]
#*# control = pid
#*# pid_kp = 70.405
#*# pid_ki = 1.025
#*# pid_kd = 1209.203

Footnotes

  1. https://www.klipper3d.org/ ↩

  2. https://all3dp.com/2/g91-g90-g-code/ ↩

  3. https://www.antclabs.com/bltouch ↩

  4. https://www.klipper3d.org/BLTouch.html#connecting-bl-touch ↩

  5. https://www.klipper3d.org/Manual_Level.html#adjusting-bed-leveling-screws ↩

  6. https://www.klipper3d.org/Bed_Mesh.html ↩

  7. https://www.post-it.com.au/3M/en_AU/post-it-au/products/~/Post-it-Super-Sticky-Notes-76-x-76-mm-Neon-Pink-5-Pads-Pack-654-5SSNP/?N=4327+3291610975+3294529197&preselect=5927575+3293786499&rt=rud ↩

  8. https://github.com/supermerill/SuperSlicer ↩

  9. https://all3dp.com/2/3d-printer-pid-tuning/ ↩