View Full Version : What sized keling stepper on RF30 clone?

06-17-2008, 09:13 PM
I have an enco rf30 clone with stock 15/16"-10 lead screws, no plans on upgrading to ballscrews any time soon. Backlash is 1-3 thousandths. Im going to be milling mostly aluminum and some steel occasionally and wanted to know what stepper would be enough for the x-y axis. Theres also the quill fine feed i was planning on adding a small (< 200 oz-in) stepper to, and possibly the column crank (z axis) which i suspect will require quite a powerful motor. I have the columns geared track bolted to the column and the head is shimmed so it acts like a square column so i can move the head up and down all day long and it the head stays squared up. I dont think i want to use this in place of the fine feed though because its only 5 tpi and all that weight jumping up and down on such a light mill will lead to errors in the cuts.

Anyways, i'd like to know what everyone recommends for X, Y, quill, and column steppers. As well as a good psu or 2 psus to power it. I have a friend with a 50v 10-20amp power supply thats willing to sell it to me for around $75. Another question too, i've been hearing that the drivers will only suppy 2/3 of the max current for each stepper, does that mean i can use a 4 amp stepper on a 3amp driver? I really apreciate the help with this. So much information out there is quite over whelming and I'd really like to minimize my cost since i've already spent a load of $ on the mill, tools and linear scales.

Crevice Reamer
06-17-2008, 10:35 PM
If you measure the force at the crank handle, and the diameter of the crank, there is a formula for calculating the motor size needed.

You have that 2/3 idea wrong. If you have say, 3 motors and each one draws 4 amps (for a total of 12 amps)--then the smallest power supply you can use has to be capable of supplying 8 amps


06-18-2008, 01:46 AM
CNCMasters provides 1200 ounce nema 34 steppers for there RF30 CNC conversion. They are configured using direct drive.

You could get away with 600 ounce steppers using a pulley system for 2-1 reduction.

You can use a four amp stepper with a three amp drive however the stepper torque will be reduced.

If you want the stepper to produce its rated power output use the correct sized stepper drive. ie 3amp stepper = 3 amp drive.

Power supply must be approximately 2/3 of the combined amp draw of all motors.

Are you aware of the fact that you will not need linear scales once your machine is under Mach3 CNC control.

Jeff Alessi

06-18-2008, 02:22 AM
wow! 1200 oz in?? I was thinking 600 max. Man that really puts the cost through the roof. Have to get geckos to drive them, and a super beefy psu. The one my friends selling me might just have enough amps. Looking at around $700 and thats not even counting the column driver or stepper. I guess those scales are gonna get a work out cause i'm gonna have to start making some $ with the mill to both pay for the cnc components and to justify putting that much more into it.

Anyone have advise on the best ways to make $ with a benchtop mill?