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:

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

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

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

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

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...??

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

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.

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

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

phantomcow2,

I don't know what my future plans are with this drive, so I can only give you general details, hope that's OK. I put together a PIC 18F2331 chip with a National LMD18200 H-bridge driver. If you look on the market, you will find a commonly available drive board that uses these two components, but I can assure you, beyond that point, all similarities between my board and that one end. I saw what happened when someone began selling knock-off copies of Gecko stepper drivers, and I definitely don't ever travel down that road! (chair) I have all the respect in the world for Marriss's and everyone else's design ideas. That pair of items, though just happened to be a winning combination for the size motors I have. I liked the 18F2331 because it has a quadrature encoder interface that updates way faster than I'll ever drive a servo motor, and I liked the LMD18200 because it has loads of protective measures, requires few external components, and is very easy to drive. One PWM signal, and a direction signal. Firmware was written in assembly language with MPLAB IDE, and board design was done with Eagle lite edition. Hope that gives you ideas like it did me! :)

Brian

Any ideas on converting an a-axis to CNC?

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.....

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

-Rick

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!!!!

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

-Rick

$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

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.

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.

Just bought a used Techno Gantry Router with servos. I'm looking to buy a 3 axis control box from Camtronics. Dan Mauch offered to tune the servo motors so they would work smoothly. He also sells servo motors and encoders. This is my first foray into home CNC machining. I think servos are the way to go.

Steppers on my JGRO, and servos on the SuperMax mill. The JGRO uses 260 oz.in. Klein.... steppers

The Servo motors on the Techno router are 360 Oz/In servos. They were fitted with 500 line quadrature encoders. I'm using Mach 3 with the Camtronics Servo Controller.

I am using steppers. Never been able to get servos to work for me.
In fairness I have bought too many mismatched products and what killed me most was the varying connectors.

I worked with Dan Mauch at Camtronics. He setup the servo motors and changed the encoders. I realized that I wasn't that saavy on Servos, so I got some help. In looking around there seems to be a third option. Some places are selling stepper motors with encoders. Although I haven't gotten to see any of those in action, I like the idea that we have more choices! As far as connectors go the best course is to decide what connectors you like and then make up new cables to match those connectors. And of course you rewire the servos to match. One of the issues that caused me to change the encoders was that the old encoders drew too much current for the Servo Controller that I purchased from Camtronics. I had a very informative conversation with an engineer at Geco. He took the time to explain a lot of the issues that I was dealing with. So I'd give Geco and Camtronics both a big two thumbs up!

I worked with Dan Mauch at Camtronics. He setup the servo motors and changed the encoders. I realized that I wasn't that saavy on Servos, so I got some help. In looking around there seems to be a third option. Some places are selling stepper motors with encoders. Although I haven't gotten to see any of those in action, I like the idea that we have more choices! As far as connectors go the best course is to decide what connectors you like and then make up new cables to match those connectors. And of course you rewire the servos to match. One of the issues that caused me to change the encoders was that the old encoders drew too much current for the Servo Controller that I purchased from Camtronics. I had a very informative conversation with an engineer at Geco. He took the time to explain a lot of the issues that I was dealing with. So I'd give Geco and Camtronics both a big two thumbs up!

Good words I really should have stuck to Geckos but I wanted to go Brushless. That led me down all kinds of paths. I will re-tackle the whole over the X-Mas break and see if I can finally break through the glass wall.

I'm using a complete IH system, thats servos, with the largest power supply Aaron had available and i'll say its an awsome system with plenty of power in "x"&"y" being that i loaded an end mill with aluminum and pushed my part out from under three heavy clamps ! I do wish i had more umpf with the "z" tho as it works hard trying to do some drilling without a pilot hole, in steel.

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

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

Servos are preferred by hobbyists due to cost and secondly simplicity. I don't believe anyone sells a non hobyist metal cutting machine with steppers. I only deal with larger equipment.If you're going to put encoders on stepper motors, use servos. Try comparing the torque curves between a servo and a stepper. (stepper bad, servo good) I suppose steppers are O.K. for smaller machines.

Hey Tos,

Servos are preferred by hobbyists due to cost and secondly simplicity.

Did you mean steppers? Steppers are certainly preferred by hobbyists because they are, in fact, cheaper than servos and simpler in nature. A stepper motor can operate in an open loop arrangement while a servo must have a feedback mechanism to tell it's position. That, in turn, raises it's initial cost in addition to requiring a more expensive controller than can read the closed loop circuit.

Try comparing the torque curves between a servo and a stepper. (stepper bad, servo good)

True, but it might not matter depending on your application. For example, my open loop, stepper based machine can do about 150 IPM rapids and at that speed, there's hardly any torque in the motors. However, I don't cut at 150 IPM - I cut a 60 IPM at most and it so happens that my steppers have great torque at those speeds. For even slower feeds - like used when cutting steel, steppers output a very nice torque too.

Regards,
JR

IMO Servos might be better in many ways, but if it wasn't for the simplicity of the Steppers I would be otherwise completely discouraged to build anything CNC'd

IMO Servos might be better in many ways, but if it wasn't for the simplicity of the Steppers I would be otherwise completely discouraged to build anything CNC'd