I rearchitected the Y axis to improve on some things:
- centered belt on the plane of the Y carriage bearings
- perfectly flat belt so no induced torque on bearings
- widened belt clamp and more rigid connection to bed
- moved end stops to idler housings to protect linear bearings
- beefy no-flex idler housings
- oversized toothed 608 idler pulleys
- reduced belt angles and matching profiles for extended life
- motor moved to center to balance belt and shorten longest free span
- extra stiff motor housing with screw mount utilizing all 4 stepper points
- bearing support of motor shaft end
- tool-free belt tensioning
- tensioning does not alter belt drive geometry
- optional center foot to help support frame (damp vibrations?)
All this for FREE! You will love how solid and quiet the bed is, especially when hitting the end stops. No more bearing bashing, or layer shifts after power recovery.
This mod replaces the stock MK3 y axis and requires no prerequisite mods, though I highly recommend Taurus hard feet. This compliments both Taurus X axis and Taurus Z axis upgrades, but each are independent and can be done in stages. See also Taurus LCD as finisher piece.
Post your makes. I would love to see them.
Update I posted all the step files for some folks who are looking to hack onto a bear frame or other mods. I don't have time to do that but happy to support the cause. Note that this would require a center cross member that is not standard on the bear frame. If you still think you want to do it, I'd recommend my slot-lock attachment system as seen in TauZ and Tau brace.
Update I redid the foot so it screws directly into motor frame which is far better and simpler to print
Update I reversed the middle screws in the motor frame (R2) so the nuts are under the stepper which I should have done in the first place. Duh.
Update I made a few tweaks to simplify assembly and also accommodate a larger stepper for more torque. I am going to try this one that has good electrical specs: 48mm Nema17
Print parts as oriented. Print one of each except:
2 L spacers
2 S spacers
Print most parts 0.2 layer, 2 perimeters, 15% gyroid infill, PETG
print pulley and knobs 0.15 layer, PLA or PETG
For fun you can do a color change on pulley at 0.5mm as I did in photo.
Note: there is an another pulley in Taurus X that is identical but with a different pattern if you want to use that instead.
I recommend plating smaller parts together
Inspect parts and clean up any burrs, especially on mating surfaces.
Tau logo is for displaying on your frame to let others know you have good sense. ;-)
Remove old Y idler, motor, belt, belt clamp. Do not remove bed, rods, or bearings.
Need the two smooth idlers that came stock on X and Y axes. I'm sure you've already replaced these and they are just sitting in a drawer.
2 608 bearing
1 625 bearing (optional but recommended)
new GT2 belt
various M3 hw
I found it best to assemble with printer on its side.
Insert 3 Nyloc (or hex) nuts in each idler body. Put two pulleys on either side of 608 bearing. Insert two axles into bearing center. Insert into idler body and screw down with M3x18mm. Do both front and rear. Mount to frame with 2 M3x10mm each.
Totally optional: slide lash head into slot on rear idler. Bend around frame and use top screw to screw down lash, frame, and idler together. Makes a super strong, completely overkill connection to frame.
Snap belt clamp onto Y carriage center and screw down with two M3x10. Solid! Make sure belt opening points to the left toward the motor.
Move motor to front frame section, routing wires under center. You assemble the motor frame first and then attach to printer. I added a picture showing partial assembly when I upgraded to a 48mm stepper.
insert 2 M3x18mm screws into right side of motor frame base. Use 2 M3x12mm to18mm screws on left end of motor frame. Put two Nyloc (or hex) nuts in the center two pockets. Insert 625 bearing into pocket opposite motor mount. Insert one hex nut into motor frame and one into idler arm. Slide motor into mount with wires facing forward, and screw down with 3 M3x10mm. There is a small hole to access the grub screw on the 16T pulley. You may need to adjust it's position to be centered in belt channel.
Smooth idler has a small opening on one side and large on the other. Put one S spacer on small side and one L spacer on large side with the narrower end of each inside toward the bearing. Slide into idler arm and insert M3x18mm and screw down. You may need to nudge spacers around to get them aligned with screw. I used exacto knife tip. Do the same with pulley on top rear of motor frame and use M3x25mm screw.
Insert idler arm and screw into frame and motor with M3x30mm. Insert M3x25mm into pivot starting with flat side and snug up against head. Insert hex nut into tensioner, will be tight. Slide screw through center hole in arm with pivot side toward motor, and screw tensioner on end.
Optional but recommended: Screw Y foot into bottom center of motor frame to provide support. This is designed to work with my low profile hard feet
Thread new belt around front idler from top. You can use a hex wrench in the windows to poke the belt through. Route over idler arm pulley, under motor, over fixed pulley and then through rear idler starting at the bottom. Pull forward and slide end into belt clamp using half the clamp span. Pull the belt to take up some slack, but not snug. The idler arm should be able to rotate maybe 10 deg from vertical. In the photo you can see I cut my belt short so idler is very extended. Still works, but less ideal. Cut new belt so it meets the other end in the center of the clamp and insert into clamp.
Push the tensioner screw and arm so that you can hook the pivot into a recess behind the arm. Screw knob until belt it tight but with some give. Too tight is very bad and causes ringing. Double check that pivot is seated correctly in motor frame.
Test range of motion of bed and make sure clamp hits idler bodies on each end first and not the bearings.
Set printer back upright. Rotate Y foot toward front of printer to extend foot and increase tension. Do only until makes contact with desk, no tighter. Main four feet should carry the load, not the center foot.