Need Help!- What type stepper do I need?

[TarHeelTom]

Have a Bridgeport cnc with the big original steppers. Just acquired a 12" rotary table (manual). Need to remove the manual handle and install an inline stepper motor.

It appears that it take 90 revolutions of the handle to turn the table one complete turn, so it doesn't appear that I'll need any gear reduction. And I haven't built the adapter to mount the motor, and won't until I have a motor and flex coupler in hand.

Anyone have any suggestions as to the spec's I'll need for an adequate stepper motor for this rt?

Thanks

Tom

[James Newton]

This web page:techref.massmind.org/techref/io/steppers.htm#Estimating Has a little calculator that will tell you the wattage (amps * volts) you would need for a given torque measurement. If you measure the torque, then run that through the calculator, along with the max speed you want to turn it, then you can build a system that puts out that much power.

[TarHeelTom]

Originally Posted by James Newton If you measure the torque,

How do I measure the torque?

And by Max Speed, you mean the rpm as measured at the hand crank?

It takes 90 turns of the crank to make one revolution of the table, and I suppose that 4 rpm of the table would be an adequate rapid speed, so then I need probably 360 rpm at the crank/stepper.

Thanks for the help.

Tom

[James Newton]

High performance stepper articles. Part 2 - How to measure torque. Roman Black - Jan 2001 explains how to measure the torque produced by a stepper motor, but the same methods may be used to measure the torque of a load as well. Since you already have a handle, you don't really need to make the lever... just measure the weight required to make the handle turn... you can even use a postal scale or spring scale.

[TarHeelTom]

Originally Posted by James Newton explains how to measure the torque produced by a stepper motor, but the same methods may be used to measure the torque of a load as well. Since you already have a handle, you don't really need to make the lever... just measure the weight required to make the handle turn... you can even use a postal scale or spring scale.

Thanks again. So I'm just trying to measure the breakaway torque need to start the handle turning, then add a bit of a safety margin over that.

What rapid speed is deemed adequate or desirable on the A axis? Would a 4 rpm rapid for the table be adequate? Seems like the Bp does rapids at around 90 ipm.



Thanks again.

Tom

[James Newton]

rapid speed is really for you to decide... there may be factors that matter in that decision (tool cutting speed?) but I don't know enough to advise in that area. Good luck!

[TarHeelTom]

Originally Posted by James Newton rapid speed is really for you to decide... there may be factors that matter in that decision (tool cutting speed?) but I don't know enough to advise in that area. Good luck!

Don't think that tool cutting speed is a factor, as (if I understand correctly) rapids are normally only used when NOT actually cutting.

Other question. Seems to me like the best way (on my rotary table, at least) to drive it is with the motor inline with the hand wheel shaft, using a mount turned to size with a flange on each end. But inside I need a flex coupler of some sort. Better part of 1" long on each end, 1/2" hole on one end, about 0.7" hole on the other end.

Anyone got a good source for these couplers?

Thanks

Tom

[xatxtal]

Originally Posted by TarHeelTom Other question. Seems to me like the best way (on my rotary table, at least) to drive it is with the motor inline with the hand wheel shaft, using a mount turned to size with a flange on each end. But inside I need a flex coupler of some sort. Better part of 1" long on each end, 1/2" hole on one end, about 0.7" hole on the other end. Anyone got a good source for these couplers? Thanks Tom

Hello Tom
If you put " stepper coupler " into ebay search a number of types come up.
I hope this helps.

I have a question relative to this thread, and that is is there any software or something I have missed in EMC2 that enables one to divide accurately, useing a rotary table, using a stepper motor.
Many thanks
Trev

[intel1]

Hello,

I wanna convert our Lathe Machine into CNC Machine. My Lathe
uses 1 HP (Horse Power) spindle Motor power & used for manufacturing
steel, brass, aluminium parts. For that, we need all equipments
e.g. Stepper Motors, drives etc... that will be suitable for my lathe.
Please suggest a good Kit for my requirements.


Regards,
-Nitin Jain

[TarHeelTom]

Originally Posted by xatxtal Hello Tom If you put " stepper coupler " into ebay search a number of types come up. I hope this helps. I have a question relative to this thread, and that is is there any software or something I have missed in EMC2 that enables one to divide accurately, useing a rotary table, using a stepper motor. Many thanks Trev

Thanks, I'll try ebay.

The A axis is driven in degrees of movement (rotation). Just use a simple four function calculator to determine how much rotation you want.

For instance, to divide a circle into 5 parts, 360 / 5 = 72 degrees. So if you are starting from zero degrees, simply command
g00 a72
......
g00 a144
.....
g00 a 216
.....
g00 a288
.....
g00 a360

If this isn't what you're trying to do, ask again.

Tom

[xatxtal]

Originally Posted by TarHeelTom Thanks, I'll try ebay. The A axis is driven in degrees of movement (rotation). Just use a simple four function calculator to determine how much rotation you want. For instance, to divide a circle into 5 parts, 360 / 5 = 72 degrees. So if you are starting from zero degrees, simply command g00 a72 ...... g00 a144 ..... g00 a 216 ..... g00 a288 ..... g00 a360 If this isn't what you're trying to do, ask again. Tom

Tom
Many thanks it seems just what I need.
I have never looked at the A axis, I will now give it some study.
We have an old saying " cannot see for looking " I am guilty of that!
Thank again.
Trev

[TarHeelTom]

Originally Posted by TarHeelTom Thanks, I'll try ebay. The A axis is driven in degrees of movement (rotation). Just use a simple four function calculator to determine how much rotation you want. For instance, to divide a circle into 5 parts, 360 / 5 = 72 degrees. So if you are starting from zero degrees, simply command g00 a72 ...... g00 a144 ..... g00 a 216 ..... g00 a288 ..... g00 a360 If this isn't what you're trying to do, ask again. Tom

Another way to do it is to let EMC2 do the math for you.

again, starting at 0 degrees...

g00 a(360/5)
.....
g00 a(2*(360/5))
.....
g00 a(3*(360/5))
.....
etc.