Automated probe accuracy testing

probe_accuracy_test_suite.py is a collection of tests to help checking probe accuracy, precision and drift under different conditions.

Default Tests Included

• 1 test, 30 samples at each bed mesh corners - check if there are issues with individual z drives.
• 20 tests, 10 samples at bed center - check consistency within normal measurements
• 1 test, 100 samples at bed center - check for drift

Changelog

I'm making updates as I receive feedback from the community on what tests are actually useful

• 2022-06-09: Allow passing probe_accuracy parameters and generating statistics on repeatability tests

Installation

On your printer:

curl -sSL https://raw.githubusercontent.com/sporkus/probe_accuracy_tests/master/install.sh | bash

will clone/pull this repo and install the uncessary python packages.

How to

Use python3 $HOME/probe_accuracy_tests/probe_accuracy_test_suite.py --help to see all the options

Tests

• Run all three tests: python3 $HOME/probe_accuracy_tests/probe_accuracy_test_suite.py
• Enable tests individually with --corner/-c, --repeatability/-r, --drift/-d
• Test parameters can be further specified:
  • corner test, 10 samples each: --corner 10
  • 5 Repeatability tests: --repeat 5
  • 50 probe samples drift test: --drift 50

Other options

• add --speedtest to test a range of z-probe speed. Speed parameters are entered in interactive menu.
• add --force_dock to force probe docking between tests to check docking issues
• add --export_csv to export data as csv
• add --speed/-retract for probe speed/retract distance override
• add --keep_first to force keeping first probe sample even if it's configured to be dropped normally

Requirements

Python

See requirements.txt

They will installed by installtion script above. If they are not installed - they can be installed like this manually.

pip3 install -r requirements.txt

Printer

• Need klicky macros properly configured, so that homing/leveling/probe accuracy gcodes will pick up the probe safely.
• There was an issue that prevented running PROBE_ACCURACY near the front of the bed in klicky-macros.cfg. This was fixed on 2022/05/30. Please update your config file if you see this error msg: Must perform PROBE_ACCURACY with the probe above the BED!" .

Output

All graphs and data are saved to $HOME/probe_accuracy_tests/output. Enable csv export with --export-csv flag.

Plot examples:

Terminal:

Interpreting results

• The green area is the middle 50% range of your samples. The narrower this band is, the more precise your probe is.

• The red area falls outside of median +-0.005mm. If you have a lot of samples in the red area, you MAY have issue (but not necessarily).

• Graphs are fancy and helpful to find glaring issues, but it is unnessary to chase the most perfect graphs.

• If your repeatability range is 0.1mm or less, it should be sufficient to produce a good bed mesh. Increasing probe sample count (set in printer.cfg > [probe] > samples) can help sometimes.

  

Common Issues

• On voron V2 printers, the most common issue is loose z-belts. An example from a printer with loose belt:
• Getting probe sample exceeding samples_tolerance error: increase [probe]:sample_tolerance to 0.02. This has no effect on the actual accuracy of your probe.