Dual Auto Leveling Prusa i3 Reworked X-Idler Tensioner with T8 Leadscrew

thingiverse

These parts are drop-in replacements for the Prusa i3 Reworked X-axis assembly and are meant to work seamlessly with the Herringbone Prusa i3 Reworked Greg's Extruder (http://www.thingiverse.com/thing:1446842). The modifications made to the original parts include: X-IDLER 1. A belt tensioner has been added, which can be used with either a 4x40mm bolt or a 5x40mm bolt. A nested nut trap is designed to catch the smaller 4mm nut. The tensioner has an effective range of 11mm and features an access port on the side for easy installation or replacement. It's been optimized around the 608ZZ bearing and works in conjunction with the included bearing guide, allowing a 0.75mm clearance between the edge of the bearing guide and the tensioner body to prevent belt slippage. 2. The inner diameter of the 8mm smooth rod holes has been reduced to make it more difficult for the rods to slip out. Additionally, the ends of these holes have been closed up to keep the rods from escaping through the back. 3. The Z-axis nut trap has been removed and replaced with a platform that catches a floating Z-axis switch. This design follows Crota's March 17, 2014 technique (http://www.thingiverse.com/thing:273805), but implements it in a way that mirrors the Robo 3D R1 printer's setup. The Marlin firmware needs to be modified as explained by Crota for this feature to work. 4. Multiple versions of the floating Z-axis platform are included to make this part compatible with printers using 5mm threaded rods, 8mm threaded rods, and T8 leadscrews. X-MOTOR-END 1. Similar to the X-Idler above, the Z-axis nut trap has been removed and replaced with a platform that catches a floating Z-axis switch. Having dual limit switches on both ends of the X-axis assembly eliminates the risk of the nozzle being driven hard into the print bed in case one axis is lower than the other. This setup also allows for separate measurements to be taken on both sides of the print bed, enabling accurate calculation of the printing surface's orientation relative to the nozzle. 2. Similar to the X-Idler above, multiple versions of the floating Z-axis platform are included to make this part compatible with printers using 5mm threaded rods, 8mm threaded rods, and T8 leadscrews. How I Designed This Inspiration for modification came from observing how the Robo 3D R1 manages auto-leveling of its bed. The Robo 3D attaches the Z-axis limiting switch to the X-axis mounts so that it 'floats' just under the X-axis. When the nozzle touches the build plate, the limit switch is triggered. In this case, an OMRON 5E4 T85 (http://www.mouser.com/ds/2/307/SS_1110-14757.pdf) switch is used. The limit switch button is pressed down by the weight of the X-axis when it's not touching the print bed, keeping the switch in the open position and preventing a signal from being sent to the Ramps board. When the nozzle touches the bed, the switch goes up, closing the circuit across terminals 1 and 3 on the OMRON 5E4 T85 switch, triggering a z-axis trigger event on the Ramps board. Using the Robo 3D as a reference design, the existing Prusa i3 Reworked X-axis idler was modified to accommodate a 'floating' or 'following' Z-axis limit switch that hooks into the X-idler body. The Prusa i3 Reworked modified X-idler with floating Z-axis limit switch has been designed for seamless integration. The Robo 3D X-Motor-End, also with floating Z-axis limit switch, provides a comparable setup. A side-on view showcases how the Z-axis switch hooks into the X-idler body. A top view of the Robo 3D's Z-axis hook offers further insight into its design. The mount plate can be easily switched to hold nuts for 8mm and 5mm threaded rods or to hold a T8 leadscrew nut, offering versatility in its application.