ANET A8 optical z probe (BLtouch like with servo)

thingiverse

My trusty inductive probe suddenly bit the dust (LED always ON) after just six months of reliable service... I hastily ordered a replacement from eBay China, but since it would take at least four weeks to arrive, I decided to build an optical probe instead. To my astonishment, it's turned out to be incredibly accurate. The idea is to keep things minimal with just a flag attached to a metal pin moving between the fork of an optical IR sensor. The design allows the pin to swing freely under gravity, and a cheap RC servo motor will park and release the probe. After only a few days of operation, I'm convinced that the optical probe has numerous advantages: - It's much lighter (the inductive probe weighs 80g) - It gets closer to the nozzle - It's less intrusive, with the pin retracting nearly to the level of the heatblock bottom, making it easy to clean the nozzle - It's very accurate - It senses the top of the glass rather than under it like inductive probes do - And it's dirt cheap: you can get one for less than 3 euros! I wanted to position the probe as close to the hot end as possible and managed to squeeze it into the back left corner, just behind the left fan. It's working beautifully, and here are the results of a repeatability test run under MARLIN with M48 GCODE: 12:18:09.925 : M48 Z-Probe Repeatability Test 12:18:44.120 : Finished! 12:18:44.120 : Mean: -0.140000 Min: -0.141 Max: -0.137 Range: 0.005 12:18:44.120 : Standard Deviation: 0.001483 As you can see, the range is a mere 5 microns, and the standard deviation is less than 2 microns – better than the accuracy of the printer's other parts! Check it out in action here: https://youtu.be/GwbwwtUL2Po EDIT: For those who like a cover, there's one available!