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104 lines
4.9 KiB
Markdown
104 lines
4.9 KiB
Markdown
Frequently asked questions
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==========================
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### How do I calculate the step_distance parameter in the printer config file?
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If you know the steps per millimeter for the axis then use a
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calculator to divide 1.0 by steps_per_mm. Then round this number to
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six decimal places and place it in the config (six decimal places is
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nano-meter precision).
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The step_distance defines the distance that the axis will travel on
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each motor driver pulse. It can also be calculated from the axis
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pitch, motor step angle, and driver microstepping. If unsure, do a web
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search for "calculate steps per mm" to find an online calculator.
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### When I restart my micro-controller the device changes to /dev/ttyACM1
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If the device sometimes changes from /dev/ttyACM0 to /dev/ttyACM1 then
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ssh into the host computer and run: ```ls -l /dev/serial/by-id/```
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The name found in the above command is stable and it is possible to
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use it in the config file. For example, an updated config might look
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like:
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```
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[mcu]
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serial: /dev/serial/by-id/usb-UltiMachine__ultimachine.com__RAMBo_12345678912345678912-if00
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```
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Be sure to copy-and-paste the name from the "ls" command above as the
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name will be different on each printer.
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### Can I run Klipper on something other than a Raspberry Pi?
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Klipper only requires Python running on a Linux (or similar)
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computer. However, if you wish to run it on a different machine you
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will need Linux admin knowledge to install the system prerequisites
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for the Linux distribution running on that particular machine. See the
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[install-octopi.sh](../scripts/install-octopi.sh) script for further
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information on the necessary Linux admin steps.
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### Why can't I move the stepper before homing the printer?
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The code does this to reduce the chance of accidentally commanding the
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head into the bed or a wall. Once the printer is homed the software
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attempts to verify each move is within the position_min/max defined in
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the config file. If the motors are disabled (via an M84 or M18
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command) then the motors will need to be homed again prior to
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movement.
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If you want to move the head after canceling a print via Octoprint,
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consider changing the Octoprint cancel sequence to do that for
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you. It's configured in Octoprint via a web browser under:
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Settings->GCODE Scripts
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If you want to move the head after a print finishes, consider adding
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the desired movement to the "custom g-code" section of your slicer.
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### Why is the Z position_endstop set to 0.5 in the default configs?
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For cartesian style printers the Z position_endstop specifies how far
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the nozzle is from the bed when the endstop triggers. If possible, it
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is recommended to use a Z-max endstop and home away from the bed (as
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this reduces the potential for bed collisions). However, if one must
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home towards the bed then it is recommended to position the endstop so
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it triggers when the nozzle is still a small distance away from the
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bed. This way, when homing the axis, it will stop before the nozzle
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touches the bed.
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Almost all mechanical switches can still move a small distance
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(eg, 0.5mm) after they are triggered. So, for example, if the
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position_endstop is set to 0.5mm then one may still command the
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printer to move to Z0.2. The position_min config setting (which
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defaults to 0) is used to specify the minimum Z position one may
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command the printer to move to.
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Note, the Z position_endstop specifies the distance from the nozzle to
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the bed when the nozzle and bed (if applicable) are hot. It is typical
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for thermal expansion to cause nozzle expansion of around .1mm, which
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is also the typical thickness of a sheet of printer paper. Thus, it is
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common to use the "paper test" to confirm calibration of the Z
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height - check that the bed and nozzle are at room temperature, check
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that there is no plastic on the head or bed, home the printer, place a
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piece of paper between the nozzle and bed, and repeatedly command the
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head to move closer to the bed checking each time if you feel a small
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amount of friction when sliding the paper between bed and nozzle - if
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all is calibrated well a small amount of friction would be felt when
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the height is at Z0.
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### I converted my config from Marlin and the X/Y axes work fine, but I just get a screeching noise when homing the Z axis
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Short answer: Try reducing the max_z_velocity setting in the printer
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config. Also, if the Z stepper is moving in the wrong direction, try
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inverting the dir_pin setting in the config (eg, "dir_pin: !xyz"
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instead of "dir_pin: xyz").
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Long answer: In practice Marlin can typically only step at a rate of
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around 10000 steps per second. If it is requested to move at a speed
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that would require a higher step rate then Marlin will generally just
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step as fast as it can. Klipper is able to achieve much higher step
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rates, but the stepper motor may not have sufficient torque to move at
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a higher speed. So, for a Z axis with a very precise step_distance the
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actual obtainable max_z_velocity may be smaller than what is
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configured in Marlin.
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