Home the Ender 3 Z-axis against the bed

thingiverse

This is a fully rigid mechanical modification to home the Ender 3 (or similar printers with 2020 gantry) Z axis against the bed. It's similar to using a BLTouch as an endstop (no mesh fudging), but without the need to buy any parts (except standard M3 fastners), using the original endstop switch PCB, and without the need to mount anything to the toolhead. The trick behind this, and how it doesn't need any retract/deploy mechanism, is that the Ender 3's X and Y axes can move the nozzle outside of the bed region, allowing the Z axis to go below the level of the bed. This makes it possible to mount the endstop at a fixed height where it cannot collide with the print during printing. Advantages versus stock Z endstop setup: - Better Z homing consistency for good first layers/adhesion - Instantly swap print surfaces with no re-leveling - Even print on the flat top of an existing print still on the bed Disadvantages: - Takes a bit more time to home (but this can be minimized with high travel speed). - Can crash the print head if you set it up wrong One additional difference that could be a pro or con depending on your perspective: the bed leveling wheels now *only* level the bed (relative correction between the corners); they no longer tune absolute nozzle distance. ## Installation Slide the endstop into the bracket and secure it with two 8mm M3 bolts and nuts on the reverse side (optional if the bolts self-thread sufficiently). Unless your nozzle is long enough to leave a lot of clearance, you probably want to remove the metal arm from the endstop switch. It's prone to wearing out and imprecision issues. If you don't want to destroy your original endstop, identical replacements are available very cheap, or you can get [an alternate mount](https://www.thingiverse.com/thing:5034535) that lets you put it back in the original position without needing the arm in case you want to go back. Next, mount the bracket to the back of the gantry using two 12 mm M3 bolts and T-nuts ([printable T-nuts](https://www.thingiverse.com/thing:3050607) work fine) at whatever X position you prefer to measure at. The left edge of the bed is conveniently out of the way and needs less wire length, but measuring at the center may be preferred if you mostly print in the center and your bed has temperature-dependent warping. The top of the bracket should line up perfectly with the top edge of the 2020 extrusion. Use a JST XH-2.54 extension cable with your original X endstop cable to connect the endstop to the controller board. ## Firmware settings Your firmware **must** be setup for "safe Z homing" to move the nozzle out of the bed region. Otherwise, homing will never hit the endstop but keep pressing the nozzle into the bed forever (!!). With Klipper, I use: ``` [stepper_x] # Off right of bed, but not hitting tensioner position_max: 245 ... [stepper_z] # For CHT & original hotend; adjust to your nozzle offset position_endstop: -3.4 position_min: -4 ... [safe_z_home] home_xy_position: 245, 60 # Must be >= your nozzle offset plus enough to clear any clips, etc. z_hop: 8 ``` ## Printing the part The bracket is designed not to need any supports or significant overhangs. I printed with 30% triangle infill and 2 walls. Any rigid material is fine, but if you'll be printing in a heated chamber, you should use something suitable for the chamber temperature (i.e. not PLA). ## Customizing If you need to modify the bracket to work with a different toolhead height or fit a different endstop PCB variant, the OpenSCAD source is now included. This was a quick-and-dirty job so it's not at all parameterized except for the overall height, but it's a working starting point. ## Video https://youtu.be/nMGMHvYsMs4