CTC/ebay, E3D, Bowden, strain gauge Z probe

thingiverse

I am building a custom hot-end mount for my CTC/ebay plywood Prusa I3 clone printer. This printer uses a strain gauge for Z axis probing, which allows me to get accurate measurements of the print bed's position. The hot-end mount is designed to fit perfectly on my printer and can be easily modified using OpenSCAD source code. A slightly modified version of the mount has been super glued with a BF350 strain gauge, which, when combined with an Arduino Pro Mini and a HX711 ADC, provides Z axis probing capabilities. When the nozzle touches the print bed, the mount bends slightly and sends a signal to the electronics, simulating a limit switch. This system works with a typical operating force of around 30 grams weight. The fan shroud, printed in yellow, comes from Thingiverse's https://www.thingiverse.com/thing:2059016 design. A similar idea using a load cell can be found at https://www.thingiverse.com/thing:1248287. For more information on Z-probing, visit http://www.davidpilling.com/wiki/index.php/Zprobe. Photos of the mount with capacitive sensors and the lengthened mount with strain gauge electronics are available. The StrainStop04.zip (July 9th, 2017) file contains the source code for the Arduino software. This code relies on intercepting and passing on the Z axis stepper motor step and direction signals to the Arduino. The "hotend" scad files contain two pieces that can be edited and run once to produce the front and then again to produce the back. STL versions are included, with the front being the same for both versions of the hot-end mount. The "extruder" file is a bracket designed to hold the Mark 8 extruder to the printer. I used the design from Thingiverse's http://www.thingiverse.com/thing:1792366 as inspiration and attached M8 rods to the printer that can be slotted into the bracket. To see this project in action, check out my YouTube video at https://www.youtube.com/watch?v=K3higvTPbbA.