Auto Bed Leveling is the process of utilizing a printer’s hardware and software to define a good virtual print plane that approximates the print beds true surface so the printer knows where to create the all-important first layer.
Here’s a video of my TAZ 4 that I modified for electronic corner tap auto bed leveling. Parts of the vid are sped up for brevity:
Here’s a video showing how clean the first layer is going down:
To create this auto bed leveling feature I took the two wires leading to the z-endstop micro switch (1st pic below) and extended one to the heat sink block of my Chimera dual extruder hot end, fastening it there into one of the stock mounting holes with a screw (2nd pic below). I extended the other wire to the aluminum bed mounting plate and fastened it there driving a screw into a hole that I drilled into it (3rd pic below):
Pic 1: Original Manual Bed Leveling Microswitch
Pic 2: Z-Endstop Wire Now Fastened To Heatsink Block On Chimera
Pic 3: Z-Endstop Wire Now On Aluminum Bed Mounting Plate
Next I cut 4 squares of copper tape that I bought from McMaster (http://www.mcmaster.com/#76555a715/=122iqvc) and applied them to the four corners of the glass build plate. Probably a 1 inch wide roll or less would do for a single extruder, but I also plan on modifying my setup for both extruders. Next I soldered a new wire to each piece of copper tape. The copper tape could be applied to any build surface, for example PEI, etc; however I primarily use this printer to print PLA on glass with liquid PVA mold release brushed onto the glass because that’s how I obtain the shiny smooth surface required for some of my prints.
Pic 4: Copper Tape Corner with Wire Soldered To It
I collected the wires under the glass build plate (Pic 5) and screwed them down onto the aluminum bed mounting plate with the same screw that I used to fasten one of the z-endstop wires (Pic 6).
Pic 5: Copper Tape Wires Collected Under The Glass Build Plate
Pic 6: Copper Tape Wires Screwed Down to Aluminum Bed Mounting Plate
I set the Marlin Bed Auto Level Script to tap the four copper lined corners of my glass build plate at coordinates I defined. Then I ran the G29 gcode to start the auto bed leveling that’s shown in the video above.
Before I run the G29 code I pre-heat the Chimera hotends to 160 C and wipe them with a green Scotch Brite scouring pad to make sure they are clean for electrical contact with the copper tape. I’m printing with Hatchbox PLA and 160 C is working out really well for cleaning the nozzle without creating drips. Other suppliers and materials may require a different nozzle cleaning temperature.
When the hotends contact the copper tape a complete circuit is made indicating the z-endstop has been reached the same as if using the stock manually dialed in microswitch; except now the correct nozzle height is found automatically with electrical contact instead of manual trial and error.
Stay tuned for separate auto bed leveling with each individual hot end of the Chimera Dual Extruder