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Plans & Info » Instructions & Configuration » PRO Rack and Pinion Assembly Instructions
PRO Rack and Pinion Assembly Instructions
PRO Rack and Pinion Assembly Instructions
Thanks for purchasing our PRO Rack and Pinion Drives! This guide will help through the installation process of the most recent version (2014 update) of our Pro R&P drives. For previous model drives, please see our PRO Rack and Pinion Assembly Instructions (Previous Version).
Installation for both Nema 23 and Nema 34 units is similar. Start by installing the motor pulley on your motor. Installing this pulley at the right height will insure it is aligned properly with the drive spindle pulley:

Nema 23, approximately 0.875” off of the motor flange

Nema 34, approximately 1.25” off of the motor flange
Before installing the set screws for the motor pulleys, remove the screws and apply Loctite to them. Motor pulley set screws that have vibrated loose can cause of lost motion that is difficult to troubleshoot later on, so this is an important step.
Once the pulleys are secured to the motor, it’s time to install the hex nuts in the motor mounting plate. M5 hex nuts are used in the inner set of slots with Nema 23 motors, while M6 nuts are used in the outer slots with Nema 34 motors. A hex wrench is helpful for maintaining the orientation of the while installing them:

Nema 23 motors, M5 nut installation

Nema 34 motors, M6 nut installation.
Once the nuts are installed, gently lift the plate and set it on top of your motor. You can then install the socket head cap screws that hold the plate to the motor. Do not tighten these down completely – they will be tightened after the belt tension is adjusted.
The next step is to install the drive spindle. First, place the spindle washer over the 3/8-16 tapped hole for the drive spindle as shown:
Next, install the ground spindle shaft through the spindle, and tighten down to the plate. Most spindles ship with the shaft installed in the spindle already, held in place with a plastic hex nut. The plastic hex nut can be discarded. The following illustrations are for a Nema 34 rack and pinion drive, but the same principles apply for a Nema 23 system:

If there is some resistance to movement, spin the spindle by hand a few times and it should loosen up to spin fairly freely.
Next, install the belt over the motor pulley and drive spindle. If necessary, slide the motor towards the drive spindle to provide sufficient slack in the belt.
Push the belt down so that it is fully seated on the spindle.
Next, it is time to tension the belt. Locate the cam tensioner and 20 mm M6 socket head cap screw. Install these on the motor side of the plate next to the motor. For Nema 23 motors, the cam is installed on the inside hole (closer to the middle of the plate), while for Nema 34 motors it is installed on the outside hole:
Use a 16mm wrench to rotate the cam against the motor to apply tension to the belt. With the wrench applying torque, tighten both the M6 center screw on the cam mechanism and the bolts holding the motor to the plate:
The unit is now ready to install on your machine.
The next steps are to install the gear tension adjustment bracket on your machine, using the hardware below.
The drive plate tensioner bracket should be connected to the R&P drive using the supplied flat head screw.
The carriage tension bracket will be attached to your machine using the supplied hex bolt and washer. Note, on PRO machine kits, this bracket is only used on the gantry risers on the sides of the machine, and is not used for the rack and pinion unit on top of the gantry.
The entire rack and pinion drive can now be mounted to the machine. On PRO kits, it will connect to the attachment plates on the gantry riser for the X and A units, and to the T-shaped bracket on the top of the gantry for the Y.
To attach the drive to the either interface, first insert the long pivot shaft bolt through the collar bearing eccentric and through both bearings in the plate, then thread into the tapped hole in the interface plate.
Next, while pushing in on the collar bearing eccentric, rotate it clockwise until the collar bearing starts rotating inside of the plate. Then tighten the set screw on the side of the eccentric. This will secure the drive in position on the pivot shaft.
The last step is to install the tension spring and bolt through either the carriage tension bracket (which you installed earlier on the gantry risers) or through the back gantry support plate (on the gantry).
The tension bolt should then be tightened until the spring compresses slightly, but still has plenty of compression left. It should be tight enough to keep the gear from jumping out of the rack during motion, but does not need to be compressed very far – excessive gear wear can result from over tightening of this bolt.