What’s the best method to go about cutting my lead screw? Also, is it okay and maybe even advisable to leave a little extra length on the lead screw just in case?
Oh and 1 other question. Is the bearing that the lead screw goes through supposed to sit snugly in the 3d printed part it is supposed to sit in? mine isn’t totally loose but with a tap, it comes out. I figured it would be a more snug fit. Everything else I printed has been a very good fit.
The coupler is going to sit against it, so it should stay put. I honestly don’t even remember how snug any of mine were.
I use a chop saw to cut mine. The boogered end goes up by the stepper shaft so the machined end can play nice with the lead nut, so I don’t think it much matters. Pick your favorite power tool and have it.
As for the length, I little extra won’t hurt, I guess. I did run into an issue where everything was set up perfectly on one of my mpcnc, then I tried to choke up on a bit to leave the bare minimum out on a steel test. Couldn’t cut to the bottom of the stock, lol. Everything was so loud I didn’t realize the stepper was skipping because the z tube printed pieces were bottoming out on the top of the core assembly.
On the other hand, I may want to reuse the lead screw on a lowrider at some point, so I didn’t cut it at ALL. It sticks WAY up there. Doesn’t create any problems as long as you have clearance over the machine and your stepper motor wires are long enough to reach. Unless aesthetics are your thing. Fortunately, they are not mine
The tiny negative to a longer lead screw is that you are adding mass to the Z axis. Any mass has some impact on acceleration. The positives to leaving some extra are 1) if you ever decide to increase the Z height of the machine, it is one less thing to purchase, and 2) I find it convenient to sometimes to reach under the core and turn the lead screw by hand (I left my lead screw long).
The lead screw should not extend beyond the end of the Z axis.
Just an FYI, many users here (the regulars) can move a topic to a new section. There is a pencil near the title and the category is there. Just make a note if you want it moved, and someone will do it (or I will if I see it).
We’ve never been a terribly picky forum about categories.
I suspected as much, but, for all the time I spend on this forum, I did not know the mechanism. I noticed that people can add tags to topics. When looking at the list of tags, they are seldom used. Thoughts?
So if i was to leave the screw unaltered id need to have longer z tubes than what the calculator said according to my z height correct?
I don’t know what size lead screw you have, but the tubing will need to be somewhat longer than the leads screw. I’m away from my machine, so I cannot give you a precise measurement, but if you look at a picture of the MPCNC , the lead screw is attached to the coupler that is below the top of the tubes, and you don’t want the lead screw to extend beyond the bottom of the Z axis tubing.
The one downside to a longer Z axis is mass. I did a back-of-the-envelope calculation and came up with 2.5 to 3 oz. added for each inch added to the Z axis. This mass will have an impact on your acceleration and therefore on your max feedrate. I’ve never run tests, so I cannot quantify the impact. It may be small. But if you add 6 inches to your Z axis, you add about a pound of weight.
