Piezo underbed levelling (precisionpiezo)

thingiverse

<h1>Piezo underbed project (Ender-3).</h1> update 2019-06-13 changed abs upper washer to steel washer for higher temperature-bed printing. (above 110C. for POM) update 2019-05-10 report after two months: fantastic repeated accuracy. But I not levelling all printing because rarely not accurate the measure because dirty the head. remaining plastic on the nozzle or bed. I running levelling only the removed or changed bed glass. IMPORTANT for MARLIN USERS. restart or power cycling the printer, need setting LEVEL BED ON the LCD screen or send printing command before start the print(load last mesh data and switch on the levelling) startcode part: slicer software or Octoprint: <b>G28 M420 S1</b> ;level bed ON and load ast mesh data update: 2019-04-20 change precisionpiezo trimmer pot 1M to 100k. (first voltage divider). for more precise setting. ( because 27mm disks and spacer-ring generate too high out. voltage. update: 2019-04-14 uploaded piezo holder ring (27mm x 0.6mm) for increase sensitivy. No double sided foam. update 2019:04: changed the wire to shilded cable all piezo discs. Change 20 to 27mm discs. Change polarity if need. Better sense all position when inserting double side around 1mm tape to disc bottom side from 3M or other manufacturers. foam-rubber, not foam. should be heat resistant. Change marlin settings: a-max z:500 v-max z: 25 to higher and constant impact speed. I loosened the lever screws to easily mechanical self setting. this requires a self-locking nuts. 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 acccurate measurement: Need boring 4 to 5mm lower side washer. https://www.thingiverse.com/thing:3210021 Original soulution mounting part is assembled upper-side the bottom plate. it didn't work well for me. lose sensitivy but spring and bed heat insulation swallowed up the head impact energy. see it: https://www.thingiverse.com/thing:1091270 I rotate 180 degree the mounting pad and mounting discs with self-adhesive double side tape (thin). https://photos.app.goo.gl/Vr2EkLJEPNdwyK7b7 Need polarity change the precisionpiezo connector. Working "relase mode" staright wiring (trigger for pressure drop). Connect red wire is + pin, black wire is - pin. this is triggering for the pressure is drop. 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 <s>cold</s> and hot bed, hot nozzle. Maximum internal temperature is 40°C. Need the heated-side heat-insualtion!!!! video https://youtu.be/CjpgHudlJSM need parts: 8x m4x20 srew+ 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 2pin male XH2.54 connector (z-end)