Prusa Hephestos Lead Screw Mod

thingiverse

My Upgrade for the BQ Prusa Hephestos Lead Screw Mod. I used an 8mm lead screw called THSL-300-8D, a very common and affordable option on eBay and Aliexpress. I also added a new tensioner bracket and endstop for the smooth rods at the motor end to enable tensioning of the belt against the x-axes instead of the z-rod. This keeps the smooth rods centered and helps keep the idler end straight, which was always sitting at a slight angle before. For the tensioner two additional M6 screws are needed; I used M6x20 but anything above 12mm should be fine. For the center screw, just reuse the original belt tensioner screw. For fixing the brass nut, use eight M3x10 screws. UPDATE: To complete this mod, I also added a version with the traditional tensioning mechanism. UPDATE: 11/2016 I beefed up the tensioner bracket quite a bit for v2 because it was a bit underdimensioned and tends to bend. 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 probably need to have a brim or raft. How I Designed This: I imported the STEP from the Hephestos Github into Onshape. For some reason, the bearing diameter on the idler end was way off in the original file; I fixed this. Custom Section: CAD Model The full CAD model is available at Onshape (which is awesome!), and I also attached some STEPs: https://cad.onshape.com/documents/b4f46175ddd6425faebe5b5c Changes in Firmware: In Marlin, you need to set the steps/mm setting to 400. You can also 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}