3D Printing: How to Assemble the Prusa i3 Moving Z and X Axes

By Kalani Kirk Hausman, Richard Horne

If you’re building your own 3D printer, you will have to build up the second laser cut axis. This mounts both the vertical Z axis and the horizontal X axis. You will need printed parts before you begin.

Part Details Quantity
X end idler Used with the M8 smooth rods to make the X axis 1
X end motor mount Used with the M8 smooth rods and motor to make the X axis 1
Z axis top left mount Used to hold the vertical M8 smooth rods for the Z axis
assembly
1
Z axis top right mount Used to hold the vertical M8 smooth rods for the Z axis
assembly
1
Z axis bottom left motor mount Used to hold the vertical M8 smooth rods and the motor 1
Z axis bottom right motor mount Used to hold the vertical M8 smooth rods for the Z axis
assembly
1

You will also need mechanical parts.

Part Description Type Quantity
Threaded rod M5 rods 245mm long – used for Z axis motion Rod – Steel or stainless 4
Laser-cut X axis plate The large pre-laser-cut aluminum frame 6mm Aluminum 1
Smooth rod 320mm smooth M8 rods used for motion of the X axis Smooth rod – Steel or stainless 2
Smooth rod 370mm smooth M8 rods used for motion of the Z axis Smooth rod – Steel or stainless 2
Linear Bearing LM8UU linear bearings for X and Z axis motion Motion 7
Ball bearing 624ZZ ball bearings for X axis belt idler Motion 1
M4 bolt 25mm M4 bolt for Idler Fastener 1
M4 nut M4 size plain or locknut type Fastener 1
M4 washer M4 size plain washer Fastener 6
M5 nut M4 size must be plain type as this is used for the Z
motion
Fastener / for motion 2
M3 bolt 16mm M3 bolt for fitting Fastener 16
M3 washer M4 size plain washer Fastener 6
NEMA 17 motor NEMA 17 motor 1.2A to 2.5A rated. Motion 3
GT2 gear Fit onto the NEMA 17 motor for X axis Motion 1
5mm flexible tube Two 20mm sections of flexible 5mm tubing – used to couple
motors to M5 threaded rods.
Motion 2
Tie-wraps 100mm long 3.2mm tie-wraps to secure linear bearings and drive
belt.
Fastener 8

To perform the assembly, follow these steps:

  1. Assemble the X idler:

    1. Slide the M4 25mm bolt with an M4 washer fitted into the X idler printed part.

    2. While sliding in the bolt, add an M4 washer, 624ZZ bearing, and another M4 washer to the inside of the X idler printed part.

    3. Fit an M4 washer and M4 nut onto the end of the M4 bolt.

    4. Push two of the LM8UU linear bearings into the idler mount. You may need to use some force to insert these, but be careful not to damage the plastic part.

  2. Prepare the X ends with linear bearings:

    1. Push two of the LM8UU linear bearings into the X motor mount; as with the idler end, use caution when fitting.

    2. Slide two LM8UU linear bearings onto one of the 320mm M8 smooth rods; slide one more LM8UU linear bearing onto the other 320mm smooth rod.

    3. Fit the ends of the smooth rods into the X motor ends and X idler ends. Do this carefully they should be very tight and should be pushed all the way in.

  3. Fit the X and Z axes together. Use the following steps for orientation:

    image0.jpg

    1. Slide the two 370mm M8 smooth rods into the LM8UU linear bearings that were fitted into the X axis ends.

    2. Push fit the top left and top right printed mounts to the upper ends of the two 370mm M8 smooth rods.

    3. Push fit the bottom left and bottom right printed mounts to the lower ends of two 370mm M8 smooth rods.

  4. Fitting the Z and X axis to the laser-cut frame:

    1. Position the assembled axis over the laser-cut frame.

    2. Fix the top and bottom Z axis printed mounts to the laser-cut frame with 8 x M3 16mm bolts.

  5. Fitting the X Carriage:

    1. Place the printed X carriage onto the three linear bearings that were fitted to the horizontal X smooth rods earlier.

    2. Secure the carriage to the LM8UU linear bearings with six tie-wraps.

      image1.jpg

  6. Fit the motor and drive belt used for motion of the X axis. Use the following steps for orientation:

    1. Fit a NEMA17 motor to the X motor mount using three 16mm M3 bolts.

    2. Slide a GT2 pulley onto the motor shaft and secure with grub-screw.

    3. Wrap the second GT2 drive belt around the GT2 pulley on the motor, guide this along towards the X carriage; the other end of the belt should wrap around the X idler bearing and also meet in the middle at the X carriage.

    4. Secure the belt tightly to the X carriage using tie-wraps.

  7. Fit the vertical drive motors and the fine pitch M5 drive screws that are used for Z motion and lifting the X carriage up and down. Use the following steps for orientation:

    1. Fit a NEMA17 motor to the each lower Z motor mount using three 16mm M3 bolts.

    2. Thread one M5 plain nut onto each M5 threaded rod.

    3. Push 10mm of the flexible tube onto one end of each M5 threaded rod.

    4. Insert the 10mm of flexible tube onto the Z motor shaft. You will need to raise the X carriage or hold it out of the way while doing this.

    5. Finally, align the M5 threaded rod with the X axis motor mount and idler mount. The M5 nuts should push into the plastic mounts and the X axis will rest on these nuts.