Help with ball screw gearing what reduction
What would be the best amount of reduction to use?
On the y axis I have a 1.5 inch ball screw running across 40 inches with 2 thk hsr 45
Linear rails with 2 bearings on each they are stiff and so is the ballscrew
I plan on using a big Nema 34 or larger servo or stepper

y axis (http://www.cnczone.com/gallery/data/505/medium/y.jpg)

I forgot to mention it is a .5 pitch ballscrew
I am still putting in the new balls I orderd 300
but ran out wile loading it so orderd some more
here is a pic from the gallery (http://www.cnczone.com/gallery/data/500/medium/ball-screw.jpg)

There are really too many factors involved to give you a good answer. Steppers may not need to be geared at all. And gearing steppers can be detrimental to high speed performance. Gearing a servo depends on the particular servo to an extent. Different servos have different top speeds. You generally want to gear according to that. How fast you want the machine to move also needs to be considered.

yes I have been thinking that I should have included more info most of the time I want to run a 2.5 horse 6700 rpm
motor that connects to the r8 spindle with a 1.25 motor pulley
and a 3.5 spindle pulley so my top speed will be around
2400 rpm I want to mill aluminum
high speed is not that big of a concern for me at this point
my concern is it seems to take about 20 lbs of force to move the stage (same with the top off about 10 lbs each side)
then the ball screw doesn’t turn real easy plus by the time I am done I figure the mass moving back and forth will all weigh about 120 lbs at least
I have been building for rigid but may have got carried away
most of the stuff I see is more for wood and lighter
and faster and just connects directly to the ballscrew
but you see my dilemma I am new at this and just want some advice if I should go to about 10 to 1 or a place to start
I think with some of the setups if you go to 30 to 1
or above gear drives you don’t need a brake
but I guess you would have to check that on individual unit
so anyone that knows math that has a idea or someone
that has a heavy ass thing like this moving back and forth
I would love to here from

got some great ideas on the x axis from members
I will have to take it back apart to implement them
but I am sure it saved me allot of time and money
in the long run and am grateful
:)

You really need to let us know exactly what stepper or servo you'll be using. Without that, you can't determine what gearing to use.

Possibly I am putting the cart before the horse
I had planed on trying to get the mechanical stuff done first
I just don’t think I am learned enough on the motors to
Know what to buy I have been reading the servo forum
for some time as I was leaning that way
and possibly gecko 340s
but I was hoping to continue building for a wile
and soaking up more info on motors before I buy
I just read the robot builders bonanza well most of it already
and that explained allot but
I don’t know enough about them yet to buy something
that parts are readily available for and works good
or even what would work best for me
is there 2 or 3 you could recommend then
I could go read up about them on their site. and a size recommendation?
I would just as soon buy one to big
Besides I would like to ad another axis or 2 later and one would be on the x
so I need to account for that now I figure that will be another 40 lbs or so but have not came up with anything I like yet for the rotary part
I will start looking at motors I can see how you would need to figure the torque of the motor
Before you figure the gearing thanks

I want to run a 2.5 horse 6700 rpm

This is not in reference to your gearing ? but an observation.

With that much HP and available RPM, why limit your spindle to 2400 RPM, if you are not going to control the rpm electronically perhaps you can add step pulleys to take advantage of the 6500 limit. Cutting aluminum and high RPM get along fine (Most of the time), the higher RPM potentially allows for faster feed rates as well as a nicer finish.

Ken

well the parts went together so easy and it is electronic vairable speed here is a picture

http://www.cnczone.com/gallery/data/505/medium/spindlepower.jpg

it is a treadmill I bought for 20 bucks at a thrift store thay where happy to get rid of it worked great proform brand if I remember right I bought the r8 spindle at

http://www.littlemachineshop.com/products/product_view.php?ProductID=1944

and the pulley just about went right on the belt and everything looks like it will work
I have all the electronics just need to look I think I can put the tach on also but you bring up a good point

I thought for fast milling I could switch over to a router
but I have a r8 milling machine and now I can use the existing tooling I have

just seems like allot more options
I hear what you are saying and it would be nice to go faster but I am hoping to be able to switch power heads
for sawing and grinding and routing and milling and such

by mounting them all to a standard mounting plate with alignment registers that I will make a jig for so I can duplicate it whether this is realistic in my reality waits to be seen thanks