Semi-automatic Bed Level Probe

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This is a simple, low-cost bed level probe based on a micro-switch that gets the job done reliably. It's semi-automatic in nature since you attach it to the extruder, run the calibration routine (G29 in Marlin or G32 in Repetier), and then remove the probe. This setup doesn't add any weight to the print head, which is a nice plus for Delta or Bowden based printers. As long as you don't bump the printer or change the bed plate, re-calibration isn't needed. It was designed to be quick-mount: it slides right onto the effector plate on Kossel (8mm thick one) and takes only a few seconds to mount on other plates that are 8mm or less. The jaw is adjustable and tightens for increased repeatability. In terms of height, it should work for any hot-end that's less than 65mm in total height from wherever the probe attaches, which means both the j-head and the longer clones will fit just fine. In terms of accuracy: I get a 20 micron repeatability but can't say how much of that is due to the printer versus the probe versus the switch. The bottom line is all those combined are less than 20 microns, which is more than sufficient for most prints. If you're discouraged by manual probes and still waiting for that fully automatic sensor, you might be surprised at how much of a difference this little thing can make: consider it will at least allow you to get the printer in shape where it can actually print parts for a more complex probe. This should be lot more precise than the Kossel original allen key probe and more reliable than the newer FSR solution (at least for the time being) since it allows you to have a heated bed as well as a super-tight bed plate (safe removal of stubborn prints). The large version is compatible with both 1/2" (small) and 20mm (large) micro-switches. Additional parts needed: Note: Height maps generated with Repetier (Tools->Bed height map) and Excel.