[KEYTEEM]

it would be nice to see how many of each different system is out there'''
what make machines you have them on ?
where you purchased from?
what model and size motors?
and your overall feelings in generall like , on a scale of
1 - 10 are happy with their performance, reliability, are you glad you
went the way you did with the system you have?

yes i admit it ,i am trying to decide on where and what to buy for my
mill, IH mill , but a good place to find all this info in one spot (or 2)
would be nice info for all,,,,,,,,,
stepper vs servo ,,,,,,,,,,
let the torque wars begin :cheers:

[JRoque]

Hello. Steppers here, 150oz. They are cheap, reliable and less complex than servos. On the flip side, most are slower and can lose steps if they are not in closed loop.

JR

[pstockley]

You should have added an option for both! I will be using both soon. The lathe will use servos and the mill steppers.

[Mr.Chips]

Hello. Steppers here, 150oz. They are cheap, reliable and less complex than servos. On the flip side, most are slower and can lose steps if they are not in closed loop.

JR

What is a "Closed Loop"

Thanks
Hager

[JRoque]

Hey Hager,

Closed loop is a term used to describe a feedback method telling the controller and/or computer where the motor is. To close loop a motor, you could add an optical encoder to the shaft and connect it to your controller, if supported. Servos need this because they would otherwise spin uncontrolled not knowing when to stop. Steppers get by without one because you control the number of steps they take.

I used to work on IBM mainframes many moons ago. Those big boxes came with big ol' printers. These used servos to feed the paper and spin the character "chain" (long story). When the optical encoder went bad, the paper feed would spin top speed and feed the entire box of paper in a matter of seconds rolling it up in a tight pack under the printer hood. Those were the days.

JR

[eman5oh]

I am running 640oz on a mini jig borer retro fit. Powered by Gecko G201's @ 54Volts. I get 270 ipm rapids. I would say that I am happy with them. I had originally purchased 3 servo's for the retrofit and ended up selling them before ever using them. The steppers are smooth and prenty fast enough. I plan on adding a G100 grex and encoders soon. I have not lost any steps yet and do not want to ,but it is always in the back of my mind. If I had used the servo's I would have had encoders from the start and would not worry. Jus t my .02

[cavediver]

eman5oh,
Curious as to what your using as a drive system (screw size, type, and pitch). I am considering the same drive/motor setup. Also, what sort of force do you have to apply (in a test situation) before you are able to force an axis to skip steps. 2,10, 20lbs??

Thanks,
John

[eman5oh]

It is direct drive, the motors are conected dirctly to the ball screws, (5/8-5tpi) and fed throgh angular contact bearings. As far as force to make the system stall, I am not sure, I can not hold it back. The other night I lost steps is when my computer went to check for a virus def file update during a rapid move. I have since reinstalled the os and optimised the system and have not had any more problems. I still want encoder's either with the rex or with a Rogers bob and macro to stop the machine if steps are missed. I oversized the motors for my application just for insurance, but still alway in the back of my head. I have about 20 hours of cnc cutting time on the mill.

[drawbar]

Servos.

I started out with steppers I rescued from dot-matrix printers, but I didn't put forth enough time and energy to make them completely reliable, and yes, stepper motors can be made reliable! But with my setup I got fed up with stalling steppers and lost steps. I designed and built my own servo drive boards from many many ideas from this site and the web. I'm using small Pittman servo motors (don't know the torque ratings) for X & Y, and a larger Electrocraft servo for Z. I am still running them on a fairly small MDF machine. 12" by 12" X & Y, and about 4" Z. The thing I like best about servos, they are very quiet! When the Dremel isn't running, just the whir of the servo bearings is all you hear.

Brian

[phantomcow2]

Servos.

I started out with steppers I rescued from dot-matrix printers, but I didn't put forth enough time and energy to make them completely reliable, and yes, stepper motors can be made reliable! But with my setup I got fed up with stalling steppers and lost steps. I designed and built my own servo drive boards from many many ideas from this site and the web. I'm using small Pittman servo motors (don't know the torque ratings) for X & Y, and a larger Electrocraft servo for Z. I am still running them on a fairly small MDF machine. 12" by 12" X & Y, and about 4" Z. The thing I like best about servos, they are very quiet! When the Dremel isn't running, just the whir of the servo bearings is all you hear.

Brian

Tough to argue the noise factor! Do you have any information you can share about your homemade servo driver? I might be interested in attempting this (with a much more electrically savvy friend than myself) for my next project

[george128306]

Well...I am just a beginner who is preparing to convert a mini milling machine to a CNC. Thanks for all of you who gave the idea. I know the only disadvantage of using a stepper motor is it might lose the step if you set the wrong command on your work piece. But I think if you use "stranger" stepper motor, then the chance of lose the step won't be too big....don't know am I wrong or not...??

[phantomcow2]

I am using steppers, cost and simplicity were the driving factors. DIY stepper controller schematics are a lot less intimidating to the electrical newbie. I've bought steppers from ebay, 8 wire vexta's with 118oz of torque.
I've gotten some through surplus stores as well, those are what I am using now. THese are 34 frame motors with 400oz of torque, 8 wire.
I think that if you get steppers with enough excess torque, lost steps will be much less of a problem.

I would love to get Servo's though for my next project

[jzizzi]

Any ideas on converting an a-axis to CNC?

[Pete Stenabaugh]

Does anyone have any suggestions as to where to purchase servo motors. I have found that Homeshopcnc is about the best for Steppers.......

I am looking for some servos for a mill conversion but I think I want some with about 1400 - 1800 oz in of torque. I may not need that much once I convert over to Rockford ball screws, but it is nice to have power.....

[rexstep]

Hi Peter, Thanks for that plug! Please not that we will be adding servos to our line this spring.

-Rick

[bgolash]

I`m converting to servos and they don`t cost that much more then steppers. They are more difficult to setup but once they are configured..your done. If you start out with steppers then convert, the expense is doubled. Do it right the first time and save the money for something else!!!!

[rexstep]

Servos don't cost that much more than steppers? Where are these servos?

-Rick

[bgolash]

$99.00 I paided for a 360 ozin motor. Is that too high. I paided
more for steppers. Here`s the address http://www.homecnc.info/cnc-main.html

[DRD]

Servos don't cost that much more than steppers? Where are these servos?

Been there on steppers. Runs servos and don't look back.
Steppers are dinosour controls motors.

[rexstep]

Steppers are dinsour controls motors.


-I think you means dinosaurs, but I digress. Let me point out:

1)steppers are far superior in holding torque output

2)they don't dither (hunt constantly for position) but stay exactly
put once the holding position is reached

3)better power/weight ratio than servos

4)unlike servos, they don't cook if they stall (more robust)

The view that steppers are outdated has itself become outdated as it does not take into account recent advances in driver technologies. It has even become possible to close the loop on steppers using their back EMF as an encoder signature. Newer drives operate steppers like servos and get the best of both worlds.

I would add that their are specific reasons that steppers are chosen over servos in million dollar medical equipment, the foremost being reliability with cost being secondary.

Finally, ask someone like Mariss at Geckodrives Inc. if steppers are dinosaur. He has no axe to grind with servos since he sells servodrives as well.

I am descending from my soapbox now.

Rick L.