Step 15: Y-Axis Lead Screw
You've completed the nut in the
last step. What is power transmission without a screw? In this video, I will demonstrate the holes needed for the bearing and nuts for each end and driving the screw. The process is similar to the z-axis lead screw assembly; but the screw is attached at each end. In my opinion, it's not that important to secure both ends of the screw, but you do want to make sure the free end of the screw will not flap around, so some type of mechanism to keep it in place helps.
With that said, I'm going to show you how to secure both ends... anyway. The key is to drill the proper size holes in the sides of the gantry. The skate bearing that I use to secure the lateral position of the screw (I mean to say, to keep the screw from moving in and out), I first drill a hole that has the same outside diameter as the bearing only half way through the wood. I use a 7/8" hole drilling bit. This makes a nice seat for the bearing. A nut is secured on each side of the bearing, so I drill a 3/4" hold the rest of the way through the gantry side. The same is done on the other gantry side. Oh, by the way, the 7/8" hole is on the outside side of the gantry. This way, the secured bearing and the screw can be tensioned a little, but it's not necessary. The screw is actually stabilized by the way I mount the motor, because the motor is pressed against the inside rubber piece inside the coupler and keeps the screw assembly secure.
If at anytime you don't understand some of the terms I use, please give me an email and press me to further articulate and/or define.
I've already discussed the types of screws so I will not bore you again on that subject. One additional recommendation that I will offer is to lubricate the screw. This is important. I remember with my first machine non lubricated, the sound was horrible and the screw froze. I picked up some synthetic bicycle chain lubricant and from that day on, it was magic! Interesting... skate bearings... bicycle lubricant... hmm. Maybe we should build a carbon fiber CNC with bike chains for motion. Ok, I'm babbling, it must be late.
So, now the machine is complete with all axes with linear slide bearings, and two power transmission assemblies, one for the z-axis and one for the y-axis. What's left? We still have the x nut and lead screw. Then it's off to the motors and motor mounts. I will cover the electronics before I make the router mount, just to keep you guys in suspense.