Document self-test usage, safety and stages

README.md

@@ -1,3 +1,47 @@
-# cr-x-mechanical-selftest
+# CR-X Mechanical / Thermal / Extrusion Self-Test
 
-Non-printing mechanical, thermal and extrusion self-test G-code for the Creality CR-X (run via OctoPrint before calibration)
+Non-printing G-code to exercise every subsystem of a **Creality CR-X** before
+running OrcaSlicer calibrations. Run via **OctoPrint** (upload, then print the
+file — nothing is deposited on the bed).
+
+## Files
+| File | What it does | Heating? | Extrudes? |
+|------|--------------|----------|-----------|
+| `CR-X_selftest_cold_motion_only.gcode` | Homing, X/Y/Z travel, diagonals, corners, speed range | No | No |
+| `CR-X_selftest_full.gcode` | Everything above **plus** bed heat, hotend heat, fan ramp, extrude/retract | Yes | Yes |
+
+**Run the cold one first.** If motion is clean and quiet, run the full test.
+
+## Before you start
+- **Stay with the printer** the whole time. Keep the power switch / e-stop in reach.
+- For the **full** test, **load filament** first (the extrude stage feeds ~90 mm total). ABS or any filament is fine — nothing is printed.
+- Clear the bed and gantry of tools/clips.
+
+## Assumptions (edit if yours differ)
+- Build volume **300 × 300 × 400 mm**. All moves keep a **5 mm margin** from each axis limit and **20 mm** off Z-max.
+- Bed heated to **100 °C** (CR-X rated ≤100 °C).
+- Hotend heated to **230 °C** only — safe for the stock **PTFE-lined** hotend and hot enough to extrude ABS without grinding. Cold extrusion is never commanded.
+- Bowden retraction test uses **6 mm**.
+
+If your CR-X has a filament runout sensor that halts on the extrude test, disable it for the run or ignore the trigger. (The `M runout ignore` line in the full file is a comment placeholder, not a command — remove it if your firmware flags unknown lines; most Marlin builds just skip it.)
+
+## What each stage checks (watch the LCD `M117` messages)
+1. **Homing** — endstops seek/back-off/re-tap. Listen for grinding or a crash.
+2. **X / Y sweeps** — full-width and full-depth travel, belts smooth.
+3. **Z sweep** — **both lead screws must turn together**; gantry stays level.
+4. **Diagonals + corners** — combined XY motion, no binding.
+5. **Speed check** — fast then slow moves; listen for chatter/resonance.
+6. **Bed heat 100 °C** — smooth climb on the OctoPrint graph = good thermistor/heater.
+7. **Hotend heat 230 °C** — same, no wild swings (that would mean a PID/thermistor issue).
+8. **Fan ramp 50 % → 100 % → off** — part-cooling fan spins clean, no bearing rattle.
+9. **Extrude/retract** — steady flow, no clicking or skipping on the Bowden gears; the 6 mm retract should visibly pull back.
+10. **Cool down + park** — heaters off, gantry dropped, bed presented, steppers disabled.
+
+## If something fails
+Note the **`M117` stage name** shown on the display when it went wrong — that pinpoints the subsystem. Common ones:
+- Axis grinds at home → endstop or belt/pulley.
+- One Z screw lags → coupler grub screw or binding rod.
+- Temp graph swings or bails with a MINTEMP/MAXTEMP → thermistor/heater wiring.
+- Extruder clicks → nozzle not hot enough, clog, or filament not loaded.
+
+After a clean pass, move on to PID tuning and the OrcaSlicer calibration workflow.