Piezo underbed levelling (precisionpiezo)

thingiverse

<Piezo Underbed Project for Ender-3> Update 2019-06-13 Switched to steel washers in the ABS upper washer for high-temperature bed printing above 110C, ideal for POM. Update 2019-05-10 After two months of use: Fantastic repeated accuracy. However, I don't level all prints because it's often inaccurate due to a dirty head or remaining plastic on the nozzle or bed. I only level the removed or changed bed glass. Important Note for Marlin Users: Restart or power cycle the printer and set LEVEL BED ON the LCD screen or send a printing command before starting the print, loading last mesh data and switching on levelling. Startcode Part: Slicer Software or Octoprint: G28 M420 S1 ; Level bed ON and load last mesh data Update 2019-04-20 Changed precisionpiezo trimmer pot 1M to 100k for more precise setting due to high output voltage from 27mm disks and spacer-ring. Update 2019-04-14 Uploaded piezo holder ring (27mm x 0.6mm) to increase sensitivity, no double-sided foam used. Update 2019:04 Switched to shielded cable for all piezo discs, changed wire to 20mm discs, and reversed polarity if needed. Better sensing when inserting double-sided tape around 1mm from the disc bottom side. Changed Marlin settings: a-max z:500 v-max z:25 to higher and constant impact speed. Update 2019:02 https://www.thingiverse.com/thing:2439680 pcb mount https://www.thingiverse.com/thing:933599 90-degree bracket Update 2019:01 Creality spring washers for accurate measurement: Need boring 4 to 5mm lower side washer. https://www.thingiverse.com/thing:3210021 Original solution mounting part is assembled upper-side the bottom plate, but it didn't work well for me, losing sensitivity and swallowing up head impact energy with spring and bed heat insulation. I rotated 180 degrees the mounting pad and mounting discs with self-adhesive double-sided tape. Need polarity change the precisionpiezo connector, working in "release mode" straight wiring (trigger for pressure drop). Connect red wire is + pin, black wire is - pin. Test for 50 repeat cycle M48 P50 X100 Y100 V2 E Recv: 50 of 50: z: -0.013 Recv: Finished! Recv: Mean: -0.002348 Min: -0.015 Max: 0.009 Range: <b>0.025</b> Recv: Standard Deviation: <b>0.006550</b> Works well with cold and hot bed, hot nozzle. Maximum internal temperature is 40°C. Need heated-side heat-insulation. Video https://youtu.be/CjpgHudlJSM Need parts: 8x M4x20 screw + M4 self-locking nut 4x M4x50 + nut (for bed) 10mm longer than original 4x M4 knob (smaller knob) https://www.thingiverse.com/thing:146782 2x JST connector (for 2-2 discs parallel) 50 cm 3 wire servo cable (or servo extension cable) 1x 2-pin male XH2.54 connector (z-end)