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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
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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
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
Everything in moderation, including moderation.
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.
Everything in moderation, including moderation.
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 projectOriginally Posted by drawbar
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!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?
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