Servo vs. stepper?

[rycodog]

What are they differences between these 2 types of motors, are they comparable?

[ynneb]

This is a very common question. I should make up a permanent posting for the comparisons.

In the mean time.

A stepper system is usually far cheaper than a comparable servo system.
Servos systems offer better linear torque across their speed band.
Servos can have higher counts per revolution.
Servos run far cooler than steppers.
Servos have encoders on them that give feed back to the driver cards. It is harder for a servo to lose steps. Steppers do not have feed back on them, and therefore can lose steps if the load is too great.

Steppers are cheap. The control cards are cheap. They are good for first time machine builders.
I have heard little fuss from stepper users in this forum. Most seem to be satisfied with them.

What project are you planing on doing?

[rycodog]

I'm actually looking at 2 different stock machines. The only difference that I can see between the 2 is that one uses servos and the other steppers. The cost difference between the 2 is roughly 7K, with the less expensive one using steppers.

[ger21]

Is the servo system closed loop? Do they have the same controller software?

[Al_The_Man]

Originally posted by ynneb This is a very common question. I should make up a permanent posting for the comparisons.

Benny, If you are going to post a comparison of systems you should also diferentiate between systems (servo & stepper) that either use a dedicated motion card, or a software controlled system where the control is usually through the PC parallel port.
Al

[ynneb]

Benny, If you are going to post a comparison of systems you should also differentiate between systems (servo & stepper) that either use a dedicated motion card, or a software controlled system where the control is usually through the PC parallel port. Al

Al when I said "I should make a permanent posting for comparisons" the truth is, I was really thinking that it would be good if someone who knew more about these things than me, could make up the comparison. You see, even though I am new to all this, I figure if I can contribute back even my small knowledge then it is better than nothing. Al, would you like to make the comparison? We would have it in a permanent section so that it could be downloaded by newbies. My plan is, that when these sorts of questions are asked, we can point the newbie to the file. This will save a lot of time answering similar questions. I am hoping to build a reference library within the zone.
Al, would you like to take up the challenge? I feel confident you would excel doing this comparison.
When You think about it, its a little more work than making a post. The only difference is it will be stored for ever and be read by many.

[sendkeys]

[ynneb]

I guess that is why I put in the word "usually"

[sendkeys]

hmm ok...