Prusa Hephestos Lead Screw Mod

thingiverse

My Lead Screw Mod for the BQ Prusa Hephestos. I used a 8mm lead screw called THSL-300-8D which is really common and affordable on eBay and Aliexpress. I also added a new tensioner bracket and endstop for the smooth rods on the motor end in order to enable tensioning of the belt against the x-axes instead of the z-rod which keeps the smooth rods centered and helps to keep the idler end straight (it was always sitting at an slight angle before for me). For the tensioner two additional M6 screws are needed ( I used M6x20 but everything above 12mm should be fine ) For the center screw just reuse the original belt tensioner screw. For fixing the brass nut I use eight M3x10 screws. UPDATE: For the sake of completeness I also added a version with the traditional tensioning mechanism. UPDATE: 11/2016 Turns out the tensioner bracket was a bit underdimensioned and tends to bend. I beefed it up quite a bit for v2. Print Settings Printer: Prusa i3 Hephestos Rafts: No Supports: No Resolution: 0.3 Infill: 40%+ Notes: Printed in PLA, works fine. Without a heated bed you propably need to have a brim or raft. How I Designed This Imported the STEP from the Hephestos Github into Onshape. For some reason the bearing diameter on the idler end is way off in the original file, fixed this. Custom Section CAD Model The full CAD model is available at Onshape (which is awesome!), I also attached some STEPs.https://cad.onshape.com/documents/b4f46175ddd6425faebe5b5c Changes in FIrmware In Marlin you have to set the steps / mm setting to 400 (pitch 2mm, 4 starting points thus effectively 8mm per revolution -> 200 steps per revolution * 16 microsteps / 8 mm = 400 steps / mm) Also you can increase your travel and homing speed considerably. I use the following: #define HOMING_FEEDRATE {2000, 2000, 400, 0} #define HOMING_SLOW_FEEDRATE {1000, 1000, 100, 0} #define DEFAULT_AXIS_STEPS_PER_UNIT {80, 80, 400,100.47095761381482} #define DEFAULT_MAX_FEEDRATE {200, 200, 30, 25}