Making the Ponoko RepRap Z Motor Assembly

There are three variations on the Z Motor Assembly, the conventional one using a NEMA23 stepper motor, an alternative of a NEMA17 stepper, and an experimental version using a gear motor and opto interrupter. These instructions will concentrate on using the stepper motor variant.

For those of you now interested, here's a quick mockup of the experimental Z Axis drive:

You will notice that your kit came with two types of gear for the ball-chain. One is marked with an "a", the other (remarkably) with a "b". Lay your 4.5mm (sometimes called #10) ball-chain along the teeth of the gears and see which fits best. This is best done in the shop before you buy it.

What we want to see is the chain wrapping around more than a quarter of the gear's circumference without tending to leave the notches.

Only use all "a" or all "b" gears in your Z Axis. Do not mix & match.

Do not throw the other gear away. We'll use it later. Do not throw the little crescent of plastic in the gear's centre away either if you are using an NEMA 17 motor for the Y Axis.

Start by locating the components for the Z Motor Coupling.

• 3 M3 30mm screws
• 6 M3 nuts
• 9 M3 washers

Insert washers onto three M3 30mm screws and put them into the pictured Z coupling 5mm disc. Place it upside down.

Fit the pictured gear to the Z Coupling:

Next, the 5mm disc with the locking slot (lined up with the locking slot in the gear).

Check that the 4.5mm ball chain fits between the discs. If it does not, add an extra washer to each of the 30mm M3 screws between the gear and the top disc.

Above the disk, fit 3 M3 8mm spacers.

On the spacers, put the first set of washers and three M3 nuts.

Into the locking slot, insert an M5 nut and M5 8mm grub screw, also known as a setscrew. To the stack, add a 3mm disc with an M8 hole. Fix it with washers and three M3 nuts.

Place the clear portion of this Z Coupler on the stepping motor shaft. If using NEMA23, place it on the shaft opposite the mounting lugs. The gear comes with a collet that can reduce the diameter of the hole from the NEMA 23 6mm shaft to the 5mm needed by the shaft of an NEMA 17 motor. Use it or not as needed. Screw it down onto the flat of the motor shaft. Do not crack the acrylic.

Construct a lower corner bracket using four M3 25mm screws, washers, and nuts but instead of using four layers, replace the 3mm/5mm combination with a 5mm Z Motor Bracket. It will have four motor mounting slots in the corner and an 8MM hole in the center.

Add the 8MM corner bracket part just as you did for the other three lower corner brackets using four M3 25mm screws, washers, and nuts.

Connect the Spacer and Z Motor using four M5 25mm screws, washers and nuts (no washers on the screws). The Spacer will have a large hole which fits an NEMA 23 motor, and four motor mounting slots. For NEMA17, locate the matching motor bracket that fits the stepping motor, and use M5 bolts to anchor the motor bracket to the spacer and Z Motor Bracket.

You may need to use a 5mm spacer on the M5 Z Motor bolts.

Completed Z Motor Corner Assembly:

-- VikOlliver - 14 Nov 2008
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