Improved_Z axis_mounts_by_jltx

ff8jake edited this page Aug 29, 2018 · 4 revisions


Improved Z-axis mounts by JLTX on Thingiverse

Prusa Mk3 official part files - including R2 X-carriage ends

Improved installation instructions - WIP

Z-Mount removal

  1. Move Z axis to top (either using Octoprint, or by hand after power disconnected)

  2. Disconnect power from printer

  3. Lean the printer onto it's back edge, support the top of the printer frame to keep it flat (I just used a box), while holding the bed to the front (to avoid squashing the heated bed cable)

  4. Use a support to stop the bed sliding backwards. (another small box may suffice)

  5. Remove the bolts holding each Z Motor to their mounts

  6. Remove the cable ties securing the Z Motors (do NOT attempt to remove Z motors from mounts completely yet).

  7. Slide Z Motors down slightly to expose Z Motor Mount screws. (with the Z screw-rods still attached to the X-carriage)

  8. Remove Z Motor mount screws

  9. Slide the motor mounts down slightly, and release the smooth z rods from both top and bottom mounts, but NOT from the X carriage.

  10. Twist the Z Motor screw-rods by hand to detach from the X-axis ends.

  11. The Z motor mounts can now be removed by sliding them over the end of the Z screw-rods

  12. The Z top mounts can also be removed at this time

If you are not also replacing the X Carriage ends then we can just follow the process in reverse to install the new Z mounts. That will be covered below. Continue on if you are also replacing the X Carriage ends

Replacing X-carriage ends

  1. Rest the Z motors on the floor. (The left motor cables may not reach, so it may be propped up on the chassis)

  2. Remove the left-front screw holding the black t-nut to the X-carriage idler end. Be careful to remove, and not lose, the small nut. (I recommend securing it back to the screw)

  3. Remove the other screw holding the black T-nut. Note that after removing the screw, the nut recessed inside the hole will be unsecured. (It is unlikely to fall out, but be careful just in case)

  4. Remove the black T-nut from the X-carriage idler end

  5. Remove the screws securing the x-axis pulley from the idler end, and then free the pulley. (note that the nylock nut on the back of the idler is likely to stay secured, but be careful just in case it falls out unexpectedly)

  6. Slide the extruder towards the right side since it will be used to support the ends of the X rods

  7. Holding the ends of the X rods, gradually tease the X-carriage idler end from the rods by wriggling it free. (keep the Z rod in the X-carriage idler at this time, unless you also plan to replace the linear bearings)

  8. Use pliers to remove the lock nut from the back of the idler end, and put it in the replacement X-carriage idler part (it'll be a tight fit. If you can't get it to go in then use the bolt to pull it through, but don't over-tighten, then remove the bolt again.

  9. Remove the captive nut from inside the X-carriage idler, that was used to retain the T-nut. Using a fine point Jewelers screwdriver to free it works, but it is fiddly (secure to the screw to avoid losing it)

  10. If re-using the existing linear bearings, then use an ultra-fine point 'Sharpie' (permanent marker) pen to draw a line along the linear-bearings via the gap in the X-carriage idler. This helps to ensure that they are aligned similarly when installing in the replacement part.

  11. Remove the linear bearings from the X-carriage idler.

11a. If you are not replacing the bearings then it is recommended to try to remove them with the them still on the Z rod to avoid the chance of losing individual ball bearings. This may be done by using a long thin screwdriver, or allen-key/hex-wrench to push the edge of the bearings up from the bottom of the idler housing.

11b. However, if you plan to replace the bearings then it is safe to remove the rod from the bearings first, and then push the bearings out from the top of the idler.

  1. If the bearings are being replaced then mark along the length of one bearing where one of the lines of metal ball-bearings are inside the bearing set, and mark a line on the other between two lines of bearings. (This ensures that the two sets of bearings can be aligned to touch on separate parts of the smooth steel rod).

  2. If the bearings are being replaced then put the new bearings on the smooth Z rod, being careful to slide the rod in straight, so as to not push out any of the tiny ball bearings

  3. Push the bearing sets into the new X-carriage idler, being sure to align the marks on the bearings with the channel in the idler part. Ensure that the first bearing set is pushed right to the bottom of the channel, touching against the lip. Ensure the second bearing set is pushed so that it is flush with (but not protruding from) the top of the idler part.

  4. Put the two captive nuts, used to secure the T-nut inside the new idler part, and secure the T-nut using the original screws. (this partially holds in the top linear bearing set)

  5. Push the X-carriage idler part onto the end of the X rods, wriggling slightly to help it seat onto the rods. (Be careful not to let the Z rod slide out)

  6. Ensure that the X belt is unhooked from the motor end, so that it is not under tension, and feed it into the channel in the X-carriage idler part.

  7. Align the X-carriage idler pulley with the holes in the X-carriage idler part, ensuring that the belt is around it, and then secure using the original screw.

  1. Remove the motor from the X-carriage motor mount part. (loosen the 45 deg screw locking the left-most screw in place)

  2. Remove the T-nut from the top of the X-carriage motor mount. (ensure that the captive nuts do not fall out - unlikely)

  3. Remove the linear bearings from the X-axis motor end, similarly to the other side. If re-using the existing bearings then keep the bearings on the rod while removing. If you plan to replace the linear bearings then they rod can be removed, and then install the new bearings on the rod afterwards (making sure to mark the bearings, such that the lines of ball-bearings are at 45deg to each other between the two sets of bearings).

  4. Slide the Extruder assembly towards the left side.

  5. Remove the X-carriage motor mount part from the X-carriage rods.

  6. Remove the captive nuts used to secure the T-nut to the motor mount (same steps as for the idler side)

  7. Remove the 45 deg screw from the motor mount part, and remove the captive square nut from the back of the part. (you'll likely need lots of persistent knocking the part against a hard surface to shake it out, and maybe a small jewelly screwdriver, or other fine-tipped implement to ease it out)

  8. Insert that captive square nut into the new part, and partly thread the 45deg screw, just enough to hold the captive nut in place

  9. Insert the linear bearings into the X-carriage, making sure to use the markings to align in the part, such that the lines are ball-bearings are 45deg apart between the two bearing sets.

  10. Push the X-counter motor-mount part onto the X rods (apply opposing force to the X idler part, and wriggle the motor mount until it seats fully).

  11. Feed the X belt through the slot in the motor mount, also ensuring that the belt is around the pulley on the idler end

  12. Re-attach the X motor, first using the bottom-right screw, ensuring that the belt is around the motor gear, and then the top-left screw, followed by the top-right screw. At this point the screws should be left loose so that they are only just 'bite'.

  13. Tighten the 45 degree tensioner screw to tighten the belt, just enough so that the belt is tight, and springs back to parallel when squeezed together, but so that the top-left screw can still be tightened.

  14. Tighten all of the motor-mount screws.

Installing new Z mounts

  1. Install the new and improved Z-axis motor mounts on the frame using the original screws (both sides)

  2. Push each of the smooth Z-rods into the hole in the Z motor mounts (to avoid pushing it through too far, you can hold something up against the underside of the motor mount, where the motor would normally sit)

  3. Install the new Z-axis top stoppers, using the original screws, ensuring that the top of the Z axis rods are properly located in the holes for them.

  4. Slide the X-carriage to the top of the Z motion

  5. Install each Z motor, by threading the screw rod into the T-nuts on the X-carriage, and sliding the motor assembly into the motor mount.

  6. Ensure that the tops of the screw rods sit into the recess in the Z top parts

  7. Secure each motor (loosely) using the rear two screws

  8. Insert the front pieces into each of the motor mounts

  9. Insert the front screws into each of the motor mounts, and tighten all 4 screws securing the Z motors.

  10. Replace cable-ties securing the Z-motor wiring

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