Go big or go home. That's the Taurus spirit: strength with purpose, unabashed overkill, practical innovations, a dash of style.
I didn't want to do another retread of the basic prusa design, so I gave it the Taurus treatment. But of course it is still an XZ machine so limited choices. Here's what I did:
- widened bearing stance -> resist flex, hopefully push resonant frequencies outside print bandwidth
- added backlash adjusters for Z lead screw
- perfectly flat belt drive path (except stock version)
- Tool-free belt tensioning
- tension does not affect drive geometry
- super beefy fixed (not floating) idler pulley
- reoriented print -> see note below
- motor shaft end bearing support (optional)
- full 4 point motor connection
- bearing screw clamps for easier assembly
- X rod fine tuning screws (ala MK2)
- added accessory mount point, e.g. for camera
All this for FREE! Note that the photo is a prototype. Real one is much sexier. :-)
works best with Skelestruder and some other extruder mods that level the belt.
Use the 'stock' version parts to work with stock Prusa extruder or comparable offset belt extruders. Note: I am investigating issue reported with stock extruder that fails X self test, so you may want to wait a bit.
This axis upgrade is compatible with Bear frame as well.
Backlash adjusters are experimental and optional. Idea is to remove backlash from Z axis since it uses a lead screw. These provide a gentle counter force. Additionally, I lengthened to span more than one turn (4 start screw) to average out milling tolerances, and positioned out of phase with main trap nut. Hopefully this makes Z motion more reliable and accurate.
print orientation. Who cares, right? Well in FDM you can resolve certain geometric features more accurately in one dimension vs another, depending on what you are trying to achieve. The X ends are where two axes meet, X and Z. Interestingly the Z axis has two interfaces, lead screw and smooth rod, but both use a mechanical interface, trap nut and linear bearing, that are themselves machined to high accuracy. So only the remaining X axis has a direct coupling between the smooth rod and the part. I reoriented the print to resolve this interface better for a stronger more accurate rod connection and positioning. It is so tight and snug I had to add a Eustachian tube to relieve air pressure!
This nicely complements the Taurus Y axis and Taurus Z axis, but each are completely independent. See also Taurus LCD as finisher piece.
Update 2/1/19: added r1b version of stock ends.
Update 1/7/19: r1b version: tweaked idler rod holes, improved homing edge, added cap for easy pinion access and bearing clamp. Bl adjust has broader range and should align better.
Print PETG (or similar strong filament) at 0.15 layer, gyroid 12%, 2 perimeters. You can go more if you want, but these settings already are shockingly strong.
Print 2 BL adjust, pulleys, arms, and axles, and 1 each of the other parts. I merged the two X ends into one plate so they print cleaner and more accurately.
use the 'stock' version of X motor, X idler, T swing to use the stock extruder. stock X motor has a large overhang. If you have trouble printing, try the new constrained supports.
For big pulley, you can do a color change at 0.5mm for added style. Check out alternate style included with Y axis. They are interchangeable.
BL adjust is a special recipe. Follow these steps exactly; deviate at your peril.
PETG (or better yet Nylon? Or even Igus J260-PF )
0.1 layer height
turn off: ensure vertical wall thickness
turn on: avoid crossing perimeters
infill: honeycomb, then 0% (trust me)
Filament: cooling on full
printer: 0.1 lift Z
load generic modifier block 30x30x4mm high
center over part to cover cap using stupid sliders or type in -15, -15
add '+' 20% fill density
slice and go to preview. Should see honeycomb in cap, none in shaft. This is important for clean print.
Print and you should get nice clean threads with no string jungle. See reference picture below.
This will be fun. Remove old X axis. Save parts.
You will also need:
- 1 608 bearing
- 1 625 bearing (optional)
- 2 623 bearings (you may already have these from printed idler)
- new belt (a bit longer)
- various M3 hardware
Thread spacer onto Mxx18mm screw and snug against head. screw on square nut and tighten against spacer. Add hex nut to T knob and slide in slot of idler end. Slip prepared screw into square hold down to knob and turn knob to pull screw until it bottoms out. Head will be nearly flush.
Put two 623 bearings inside swing. Slide M3x16mm screw through one arm, swing, bearings, second arm. Arms are oriented to hex hole faces out. Screw on hex nut until it hits arm. Spin arm to tighten some, Should still pivot. Check that bearings spin smoothly. slide tension cartridge into slots of idler end from where pulley will mount. You will see nut through rear window. rotate down so basket bottom is against the tensioner screw head.
insert hex (not square!) nuts into slots along Z lead screw. Insert square nuts elsewhere. Make sure three linear bearings are already mounted on the X rods. Wipe thin layer of super lube on rod ends and press fit into motor end. Look through window on top to see the it inserted all the way. Make sure other rod ends are same length. Now press on idler end using window to confirm full insertion. Rejoice in the supreme fit. Lightly screw in 2 M3x8mm screws into holes at rod ends in idler end so they just touch the rods.
Insert four bearings into four bearing holes of each X end. On idler side, clamp down using 2 M3x10mm, just enough to hold bearing. Do not over-tighten. On motor side, bottom is an M3x18mm, and top is M3x30 which will screw into motor later. Add pulley covers to 608 bearing and insert axles into each side of center. Slip between arms of tension cartridge in idler end and insert M3x25mm through pulley and secure with Nyloc.
Thread the trap nut onto the Z lead screw and screw all the way to the bottom against motor. Yep. Now slide whole X axis onto smooth Z rods. Since there are no nuts the Z lead screws make no contact and you can easily slide X axis up and down. Should feel smooth. Slide to bottom and watch the top of the smooth rod. If they move inward then slightly adjust fine tuning screws in idler end to get straight. Add liberal lithium grease to BL adjuster threads and thread onto very top of Z lead screw. Re-install Z tops and slide X axis up and down. Should feel smooth all the way with no binding. Slide up to a working height and thread bottom trap nuts up into recess and screw down with 2 M3x10mm per side. Leave BL adjust floating at top for now.
Mount your extruder. Screw X stepper motor with 16T pinion attached onto X motor end with one M3x10mm in bottom right corner, tilting motor to right. Now slide new belt into top belt slot of X motor end. When it hits, use small tool to push down through top window to turn it, and push some more. Now use tool in left window to push it back to bottom exit slot. Feed and push a few times and it slides right out. Thread through extruder return slot and into bottom slot of X idler end. As you push through, turn big pulley up by hand and the belt will slide right out underneath. Warp it around pulley and slide it through the top. Pull it tight and attach to your extruder, following its instructions.
Make sure pinion is positioned so that belt is centered in channel slots. You can use opening on front to access grub to adjust. Tilt motor back straight and screw in reming holes, 2 M3x10mm and the M3x30mm you use for the top bearing clamp. Belt should not be loose. Press 625 bearing over motor shaft end so it is flush. Slide in mcap piece and make sure tab goes over bearing. Now use thumb wheel knob to fine tune belt tension. Do not over tighten or you can get print artifacts.
Thread BL adjust down into top hole. You will secure lightly with M3x18mm. These are designed to have some play. Turn until you feel some resistance, but not too tight.