¶ Positron Configurations
You want the hottest, freshest, bestest configs? Check out the PositronConfig on Github to get that latest release you crave!
¶ Sensorless Homing Sensitivity
The Positron uses StallGuard sensorless homing for the X and Y axis. We've provided a 'middle of the road' setting as stock, but variations in the linear rails, bearings, lubricants, etc. may cause these setting to not work on your printer. Even if they do work, tuning your sensorless homing can improve the reliability and gentleness of the procedure.
The driver_SGTHRS parameter in the [tmc2209 stepper_x] and [tmc2209 stepper_y] sections of printer.cfg determine the homing sensitivity for each axis. Our stocl value is 48, but that can be increased to make it more sensitive (if the printer is crashing too hard into the endstops) or decreased to make it less sensitive (of ot triggers prematurely).
Alternatively, you can do a tune the sensitivities live using the Klipper console in Fluidd or KlipperScreen:
¶ Sensorless Homing Tuning
Start by setting a high sensitivity value (we're using 60) in your Klipper console by running:
SET_TMC_FIELD STEPPER=stepper_x FIELD=SGTHRS VALUE=60
Then test the value by homing the X axis:
G28 X
This will likely cause your printer to home X too early, the higher the number in VALUE the higher the sensitivity of the sensorless homing. Re-run this command with a slightly lower value (we recommend reducing by increments of 5), testing in between, until your X axis is reliably (but still nonviolently) homing.
Once you've found a value you're happy with, save it by setting that value in printer.cfg:
[tmc2209 stepper_x]
diag_pin: ^gpio16
driver_SGTHRS: -> UPDATE THIS VALUE <-
Repeat this process for the Y axis using;
SET_TMC_FIELD STEPPER=stepper_y FIELD=SGTHRS VALUE=60
and:
G28 Y
Then save it to printer.cfg in the same way:
[tmc2209 stepper_y]
diag_pin: ^gpio25
driver_SGTHRS: -> UPDATE THIS VALUE <-
¶ Z Endstop
There have been a few iterations of Z homing hardware various versions of the Positron have used, so it's good to make sure you're set up for the right one.
First, in printer.cfg, check your [stepper_z] endstop_pin:
[stepper_z]
# endstop_pin: probe:z_virtual_endstop ; IR probe
endstop_pin: gpio3 ; microswitch endstop
position_endstop: 22 ; Comment out if not using endstop
By default, the endstop_pin is set to gpio3 for the microswitch endstop. If you have not installed a Z-endstop or otherwise wish to attempt using a probe for homing, instead use the line with the probe:z_virtual_endstop like so:
[stepper_z]
endstop_pin: probe:z_virtual_endstop ; IR probe
# endstop_pin: gpio3 ; microswitch endstop
# position_endstop: 22 ; Comment out if not using endstop
This will disable the endstop and use the IR (or other bed probe) for homing
The IR probe has been unreliable on the glass bed. While it can be used for tramming or mesh compensation with a PCB bed, we still recommend homing with the endstop if possible.
¶ Input Shaper
While all releases of the Positron v3.2 have a toolhead accelerometer, the preinstalled sd card wasn't always set up to use it. If input shaping isn't working or is throwing an error, try installing the required dependencies:
- SSH into your Positron
- Run:
sudo apt update
sudo apt install python3-numpy python3-matplotlib libatlas-base-dev libopenblas-dev
~/klippy-env/bin/pip install -v numpy
- In the Klipper console, run
SHAPER_CALIBRATE - Experiment!