Ball Screw ?

[Ed Williams]

As anyone used one of these type screws on a cnc. It looks really nice but it is 1 tpi. Anyone got any Ideas

[ger21]

Our large commercial router uses similar ballscrews. Much larger diameter, though.

[Ed Williams]

Thanks Gerry
So they would work on a small 2x3 table. Would you have any suggestion on what gearing and motor to use.

[ger21]

gearing would depend on the motor. Too many variables involved for me to suggest something. You should figure out how fast you want to be able to go, and what resolution you'd like to have, and work from there.

[Ed Williams]

Gerry
I'm very new to this and I was just trying to build a rigid table to cut small aluminum parts. I'm mainly going to be using small bits 1/8 and 1/4 so I figure I can't push it to hard. I have some small servos Static Torque: 190 oz-in
No Load Speed: 4504 RPM . I was hoping to use these if I could. But I’m open to any suggestion.
Thanks

[Al_The_Man]

You might want to play with one of the free graphical Motor sizing programs that many of the motion control sites and Motor manufacturers have, see the Parker site (Motion Village), Kollmorgan, AllenBradley just to name a few. This way you can get an idea of motor size required just by plugging in your system details, These allow you to see if your system falls into the recommended motor/load inertia ratio of 5:1 or less, which among other things depends on your required accel/decel rate.
Those ball screws are considered high lead, and require larger motor size or gearing accordingly.
Al.

[Ed Williams]

So no one has used this type ball on a small cnc.

[BobWarfield]

Ed, throw together a little XL spreadsheet and play with the variables. What you want to do is try to match your motion to the motor's torque curve. If you are going to use steppers, they're going to peak pretty low--1000 rpm torque peak. Calculate for the motion you are after (100 inches/minute?) what kind of gear ratio you get to with that ballscrew to match the motor's torque peak with that motion. Now you'll want to go check with the result is a happy one with respect to the resolution. Again, using steppers, you've probably got 200 steps/rotation. Run that through your gearing and see how far a single step moves your machine and whether that will be accurate enough to suit you.

To more directly answer your question, I haven't seen anyone use screws that are that coarse. The sweet spot is usually more like 4-5mm per turn.

Best,

BW