Probe Accuracy Testing

This is for testing the accuracy of the toolhead probe on a 3D printer running Klipper. There are two parts to this test:

1. a macro to run the test
2. a Python script to collect the results and create a chart

Installation

Create a Python environment for this script. Use ssh to log in to the Raspberry Pi, and run the following:

sudo apt install python3-venv
python3 -m venv ~/plotly-env
~/plotly-env/bin/pip install -U plotly
mkdir ~/probe_accuracy

Download probe_accuracy.py from this repository and copy it into ~/probe_accuracy/ on the Raspberry Pi:

cd ~/probe_accuracy
wget -O probe_accuracy.py https://raw.githubusercontent.com/KiloQubit/probe_accuracy/main/probe_accuracy.py

Download test_probe_accuracy.cfg from this repository and copy it to the directory containing your printer.cfg - it's ~/printer_data/config/ if you're using a current version of MainsailOS:

cd ~/printer_data/config
wget -O test_probe_accuracy.cfg https://raw.githubusercontent.com/KiloQubit/probe_accuracy/main/test_probe_accuracy.cfg

Edit your printer.cfg and add the following on a new line:

[include test_probe_accuracy.cfg]

Restart Klipper.

Test Execution

Home and level your printer (G32 on a VORON 2). Position the nozzle over the bed where you want to test the probe, probably in the center of the bed. Use ssh to log in to the Raspberry Pi and run the following to start the data collection:

~/plotly-env/bin/python3 ~/probe_accuracy/probe_accuracy.py

Warning Leave that ssh session/window open for the duration of the test.

Note If you get a FileNotFoundError, your Klipper API server socket may be in a different location. You can pass a different location to the script using the --klippy-uds /some/other/location option

Alternatively, if you don't want to leave the window open, or have a bad network connection to the Pi, you can run the script in the background, and then you don't have to leave the ssh session open:

nohup ~/plotly-env/bin/python3 ~/probe_accuracy/probe_accuracy.py >/tmp/probe_accuracy.log 2>&1 &

Run the test macro on the printer:

TEST_PROBE_ACCURACY

It will continuously run PROBE_ACCURACY while heating up the bed, soaking the bed, heating up the hotend, and soaking the hotend. See below if you want to change the temperatures or soak times. The default will heat the bed to 110, soak for 30 minutes, then heat the hotend to 150, and soak for 15 minutes - so this test will probably take over an hour to run. Get some coffee while you wait.

After the test is complete, the printer will raise the toolhead a little and turn off the heaters. The chart output should be on the Raspberry Pi in /tmp/probe_accuracy.html - copy that file to your local machine and open it. It should contain a chart showing the Z height over time, as the bed and the hotend heat up. There's also a /tmp/probe_accuracy.json file generated on the Raspberry Pi, which contains the data used for the chart. You can download it and use it to create your own chart if you wish.

All thermistors defined in your printer.cfg are plotted on the chart. Once the chart is opened, you can click on the legend of any thermistor in the chart to turn the trace on or off.

Plotting Existing Data

If you already have a JSON data file and want to generate a chart from it, you can use the --plot-only option.

~/plotly-env/bin/python3 ~/probe_accuracy/probe_accuracy.py \
    --plot-only \
    --data-file /tmp/probe_accuracy.json \
    --chart-file /tmp/probe_accuracy.html

Customizing The Test

You can pass parameters to the macro to change the temperatures, soak times and dwell behavior:

TEST_PROBE_ACCURACY [START_IDLE_MINUTES=<value>]
                    [BED_TEMP=<value>] [EXTRUDER_TEMP=<value>]
                    [BED_SOAK_MINUTES=<value>] [EXTRUDER_SOAK_MINUTES=<value>]
                    [DWELL_SECONDS=<value>] [DWELL_LIFT_Z=<value>]
                    [END_IDLE_MINUTES=<value>]

The temperatures are in Celsius. The defaults are as follows:

TEST_PROBE_ACCURACY START_IDLE_MINUTES=5
                    BED_TEMP=110 EXTRUDER_TEMP=150
                    BED_SOAK_MINUTES=30 EXTRUDER_SOAK_MINUTES=15
                    DWELL_SECONDS=1 DWELL_LIFT_Z=-1
                    END_IDLE_MINUTES=10

START_IDLE_MINUTES is the amount of time the test will wait at the start before heating up the bed.

Setting BED_TEMP or EXTRUDER_TEMP to -1 allows you to disable heating and soaking the bed or the extruder. Thus you could run a test with just the extruder and without ever turning on the bed.

DWELL_SECONDS is the approximate amount of time between running PROBE_ACCURACY commands. If DWELL_LIFT_Z is not -1, then the toolhead will be lifted to the specified Z after completing each PROBE_ACCURACY. This is intended to allow the probe to cool away from the bed between probes.

END_IDLE_MINUTES is the amount of time the test will wait after turning off the heaters at the end, while still measuring probe accuracy.