docs: Improve the BLTouch documentation (#1107)
Signed-off-by Fred Sundvik <fsundvik@gmail.com>
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KevinOConnor
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docs/BLTouch.md
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docs/BLTouch.md
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Connecting BL-Touch
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===================
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A **warning** before you start: Avoid touching the BLTouch pin with your bare fingers, since it is
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quite sensitive to finger grease. And if you do touch it, be very gentle, in order to not bend or
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push anything.
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Once you've hooked up the BL-Touch servo connector to a `control_pin` according to the BL-Touch
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documentation or of your MCU. Using the original wiring, the yellow wire from the tripple is
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documentation or of your MCU. Using the original wiring, the yellow wire from the triple is
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the `control_pin`, the white wire from the pair is the `sensor_pin`. You need to configure
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these pins according to your wiring with Klipper:
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```
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[bltouch]
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sensor_pin: P1.24
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# Pin connected to the BL-Touch sensor pin. This parameter must be
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# provided.
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control_pin: P1.26
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```
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You also most likely need to configure a homing override to first raise the z-axis, then home the x-
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and y-axis, and finally move to the center and home the z-axis. Like this:
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```
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[homing_override]
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gcode:
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G1 Z10 ; Move up 10mm
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G28 X Y
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G1 X166 Y120 F6000 ; Change the X and Y coordinates to the center of your print bed
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G28 Z
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set_position_z: 0.0
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```
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It's important that the upwards movement is high enough, so that the probe or the nozzle don't hit
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any binder clips, even if the probe pin happens to be in it's lowest state.
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Initial tests
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=============
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Before moving on, verify that the BLTouch is mounted at the correct height, the pin should be
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roughly 2 mm above the nozzle when retracted
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When you turn on the printer, the BLTouch probe should perform a self-test and move the pin up and
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down a couple of times. Once the self-test is completed, the pin should be retracted and the red LED
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on the probe should be lit. If there are any errors, for example the probe is flashing red or the
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pin is down instead of up, please turn off the printer and check the wiring and configuration.
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If the above is looking good, it's time to test that the probe responds to commands from the
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firmware. First run `BLTOUCH_DEBUG COMMAND=pin_down` in your printer terminal. Verify that the pin
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moves down, and that the red LED on the probe turns off. If not, check your wiring and configuration
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again. Next issue a `BLTOUCH_DEBUG COMMAND=pin_up` and verify that the pin moves up, and that the
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red light turns on again. If it's flashing then there's some problem.
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Now, it's time to test homing with a twist. Instead of letting the probe pin touch the print bed,
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let it touch the nail on your finger. So issue a `G28`, wait until it starts to move down, and stop
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the movement by very gently touching the pin with your nail. You probably have to do it twice, since
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the default configuration makes it probe twice. But be prepared to turn off the printer, to avoid
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damage, if it doesn't stop when you touch the pin.
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If that was successful, do another `G28` but this time let it touch the bed as it should.
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Calibrating the BL-Touch
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========================
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### Z Offset
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In order to make klipper work properly you need to tell it in which relation to the nozzle
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the probe is exactly located. Lets start with the `z_offset` - the height of the probe when
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its expanded:
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Make sure the probe is above the bed by moving the head into an appropriate x/y position:
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g0 x0 y0
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Now make klipper aproach the bed until the probe triggers using:
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PROBE
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This should deploy the BL-Touch probe, stop the run when it triggers by touching the bed.
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Now acquire the current position from the reached `z_offset` using:
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GET_POSITION
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In the output lines the `toolhead` line with the `Z:` contains the required value.
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### X/Y Offset
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In order to find the propper vertical offset of the probe you need to know a certain point of
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In order to make klipper work properly you need to tell it in which relation to the nozzle
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the probe is exactly located. Lets start with the `x_offset` and the `y_offset`
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In order to find the proper vertical offset of the probe you need to know a certain point of
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your bed. X/Y = 0 may be a good point for this, any other will do as long as you know it.
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Find it by lowering the nozzle next to it using `g0 z0.5`. Create a removeable mark on your
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Find it by lowering the nozzle next to it using `g0 z0.5`. Create a removable mark on your
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bed by i.e. using a non permanent marker.
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Now move the tip of the BL-Touch over that point by jogging there with the conrols in the `control` tab of
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Now move the tip of the BL-Touch over that point by jogging there with the controls in the `control` tab of
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OctoPrint. Once the BL-Touch is roughly over the point acquire it using the `GET_POSITION` command.
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The difference to your marked point is your `x_offset` and `y_offset` to configure in the `printer.cfg`.
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### Z Offset
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1. We start by changing the `z_offset` in the `bltouch` section of the configuration to 10. This
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setting is very wrong, but it will make it possible to move down to the right height using the
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menus. Run `RESTART` after changing it to reload the configuration.
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2. Now run `G28`, to home the printer. Take a note of the point where the pin hits the bed and use
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the menu to move the nozzle to that point. Now take a *folded* paper and put it under the nozzle.
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Move the nozzle down using the menu, in 0.1mm steps, until it grabs the paper. It doesn't matter how
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much it grabs, you are searching for the higest position that grabs the paper. The nozzle should now
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be between 0.1mm and 0.2mm above the printbed. If you wonder why we used a folded paper, the answer
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is that the granularity of the movement is only 0.1mm, or the same as a normal paper thickness, that
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means that you could easily move too far and hit the bed.
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3. Now update the `z_offset` to reflect this, by substracting the current offset (10) by the reading
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on the printer display. So if it says 8.2, then `10-8.2` = 1.8
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4. Restart the printer, issue a `G28`, move to the pin location, then `G1 Z0`, and verify that it's
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still grabbing the paper as it was before. If not, then repeat step 2. and 3. until you are
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satisfied.
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5. At this point it's a good idea to verify that the offset is close to 1mm, if not, then you
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probably want to move the probe up or down to fix this. You want it to trigger well before the
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nozzle hits the bed, so that possible stuck filament or a warped bed don't affect any probing
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action. But at the same time, you want that the retracted position is as far above the nozzle as
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possible, to avoid damage by touching printed parts.
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6. Now it's time to fine tune with a real print. First make sure that your flow rate and steps are
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calibrated properly, so that wrongly configured flow rates don't affect the calibration. Then slice
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a one layer thick object, located close to where you are homing. I recommend a simple 50x50 mm
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square.
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7. While the object is printing, use the tune menu to adjust the "Offset Z", until it looks good.
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With some practice, it's possible to find the exact point where it goes from underextrusion to
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overextrusion, but some filaments are harder to see than others. Also notice that the tune command
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does not have any effect immediately, it takes a couple of movements until the printer uses the new
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value. It might also be hard to see exactly what's happening while it's printing, so you can adjust
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for example every cm, and then find the best setting when the print is done.
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8. Update the `z_offset` configuration again by using subtraction. So if the display shows that you
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tuned the z-offset to -0.100, then it's calculated like this `1.8 -(-0.100) = 1.9`, notice the
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double minus sign.
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9. Issue a `RESTART`, and test printing the same thing, this time without adjusting anything.
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Perform steps 7-9 until you are happy.
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BL-Touch gone bad
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=================
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Once the BL-Touch is in inconsistent state, it starts blinking red. You can force it to leave that
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