Z probe repeatability test

I added a sheet of spring steel, without PEI sticker, under the ender bed cover.  It gave me plenty of room.  After messing around: I adjusted the probe nuts until the nozzle's home position was just above the bed; cinched down the nuts, then measured the gap with feeler gauges.  My nozzle was 0.30mm above the bed.  I put that offset into the firmware.

Then I ran M48 - Z-Probe Repeatability Test.  Here's the result, it looks good to me. Recv: echo:Marlin bugfix-1.1.x Recv: echo: Last Updated: 2018-07-31 | Author: (metd, Ender-3) Recv: echo:Compiled: Mar 6 2019 Recv: echo: Free Memory: 11735 PlannerBufferBytes: 1232 ... Recv: FIRMWARE_NAME:Marlin bugfix-1.1.x (Github) SOURCE_CODE_URL:https://github.com/MarlinFirmware/Marlin PROTOCOL_VERSION:1.0 MACHINE_TYPE:Ender-3 EXTRUDER_COUNT:1 UUID:cede2a2f-41a2-4748-9b12-c55c62f367ff Recv: Cap:SERIAL_XON_XOFF:0 Recv: Cap:EEPROM:1 Recv: Cap:VOLUMETRIC:1 Recv: Cap:AUTOREPORT_TEMP:1 Recv: Cap:PROGRESS:0 Recv: Cap:PRINT_JOB:1 Recv: Cap:AUTOLEVEL:0 Recv: Cap:Z_PROBE:1 Recv: Cap:LEVELING_DATA:0 Recv: Cap:BUILD_PERCENT:0 Recv: Cap:SOFTWARE_POWER:0 Recv: Cap:TOGGLE_LIGHTS:0 Recv: Cap:CASE_LIGHT_BRIGHTNESS:0 Recv: Cap:EMERGENCY_PARSER:0 Recv: Cap:AUTOREPORT_SD_STATUS:0 Recv: Cap:THERMAL_PROTECTION:1 ... Send: M48 Recv: echo:Home XYZ first ... Send: G28 ... Send: M48 Recv: M48 Z-Probe Repeatability Test ... Recv: Finished! Recv: Mean: 0.004750 Min: 0.003 Max: 0.008 Range: 0.005 Recv: Standard Deviation: 0.001346

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