Close-up of Optical Endstop Flags and X axis ACME Leadscrew
Above you can see the ACME lead screw with the anti-backlash nut. The thread size initially was 3/8″-12, 1-start on all axes (as pictured here) but was later changed to 3/8″-8, 2-start. This increased the speed of the X and Y axes three fold. It is attached to the NEMA 23 stepper motor via a shaft coupling. This shaft coupling has one side threaded in order to better secure the acme screw. You can see in the the below image that that on the other end of the acme screw there is a shaft collar which is pressed right up against the bearing in the bearing mount block. There is also another shaft collar pressed up to the other side of the bearing. What this does, is it takes a majority of the load off the smaller internal bearing in the stepper motor and puts it on that big 3/8″ bearing, thus reducing wear on the motor.
Testing the X axis
Testing of the X axis with the 3rd generation RepRap electronics was successful. As you can see in the pictures there are optical end stops at each end of the Y axis. The end stops for the X axis are actually mounted on the underside of the Y axis. The flags for the end stops are the adjustable black plastic parts that were actually printed on a commercial 3D printer. I could have printed them on the machine itself once I got it running, but I did not want to take the risk of having no end stop protection until then.
Jim, first of all, thanks for sharing all this!
I have a question regarding this part:
“You can see in the the below image that that on the other end of the acme screw there is a shaft collar which is pressed right up against the bearing in the bearing mount block. There is also another shaft collar pressed up to the other side of the bearing. What this does, is it takes a majority of the load off the smaller internal bearing in the stepper motor and puts it on that big 3/8? bearing, thus reducing wear on the motor.”
How does this exactly happen? Not having specific training in these fields I cannot understand what you are trying to say…
There is a shaft collar pressed up against either side of the ball bearing, basically securing the shaft to the ball bearing.
What was the size of threaded rods you used? 3/4-8?
…read the second sentence of the post…
Hello Jim, first of all, thank you for sharing this great project. Do you have an exact part number on your THK Linear Motion Guides?
well, I got them off of ebay, so I will need to look on them if they have a part number…