New motion type (I have never seen) Cool

[breathe]

Hey guys,

I scored today, well actually yesterday, but who cares. My work was throwing away some equipment and I got dibs on the lead screws along with the linear slides and some motors to go with. I was pretty psyched about it.

I got home and was looking at them when I realized huh these screws don't move. In fact they are fixed with set screws. They are nice clean room equipment acme threaded rod. Single start 10 tpi as far as I can tell.

Here is the cool part though how do they get the linear motion then. Hopefully the pic attaches. In the picture you can see a busted motor in goldish color at the top. That is attached to a mount that in turn sits on two linear slides carriages. There is a gear inside the box that is in front of the motor and a belt that runs to the exposed gear that you see. That red nub you see sticking out is the lead screw nut. Somehow it is attached to the gear and when you spin the motor it turn the nut which in turn moves you along the slide. Wow I thought that was pretty neat.

Any ideas why more people don't use this? Expensive? Not worth it? Inaccurate? I am thinking I will modify it and run my keling 381oz steppers on there and see what I come up with. Would love to know if I am wasting my time or if I found a goldmine.

[Al_The_Man]

It appears to be a fixed screw with the nut being spun?
Same effect as fixed nut with spun screw.
Al.

[Geof]

.....Any ideas why more people don't use this? Expensive? Not worth it? Inaccurate?...

All, some or none of the above.

Driving the nut is not common but it is done. If you did a search here on cnczone you will find it has been mentioned before. One advantage on a machine is that with a long thin lead screw faster motion can be achieved because there is no worry about the lead screw whipping. A disadvantage is that fitting the motor and drive near the nut, and mounting the nut in bearings can be much bulkier than a fixed nut with a rotating screw. Also when rotating the screw it is often possible to direct drive from the motor but a gear or chain drive is needed for the nut introducing a source of backlash. Driving the nut also introduces some complication because now the motor moves so some system for carrying the wires has to be made.

[breathe]

Yes I already was thinking about the impact of my motor riding with the gantry. Some sort of linked wire harness would be idea.

Most of the reasoning I found behind not using this method is that it is more complicated to build then the just spin the leadscrew. Buuuut since I already have most of it all setup I think this is a pretty sweet place to start.

I have linear rails. Lead screws, motors, driver, psu,

Still need software, and frame. Time to get to work.

Any more input would be appreciated. any reason not to use these in particular.

btw. I was wondering what kind of speed/accuracy I should be getting with this leadscrew. I have keling 381 oz motors, and a gecko g540. I a going to assume that the backlash on the nut is negligible. I will play with it if it isn't, but what kind of specs am I looking at. Thanks again all.