Stepper vs Servo

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Aussie
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Stepper vs Servo

Post by Aussie »

Time to upgrade my CNC to a larger model, I currently have an Axiom AR6 Pro.
I do have several options on the machine.... Servo will add about $3K what is your opinion ? is it worth the extra dollars?
Ron
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GEdward
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Re: Stepper vs Servo

Post by GEdward »

Like so many "answers", it depends. Servo eliminates the issue of lost steps for whatever reason your steppers are losing steps. Almost always steppers lose steps/position because of overload conditions. If your stepper drive setup is robust enough and your acceleration/deceleration and rapid rate parameters are set correctly then there is little to be concerned about. If your intention with the new machine is to go into industrial production mode and you need to push your tooling and machine capabilities then I'd say by all means, go for it. If the $3K premium is not a deal breaker for a little peace of mind, then again, go for it. If however, you have gotten by just fine without servo and $3K is a significant amount of money for you, I'd say don't bother.
Be advised that servo drives come in three basic flavors; servo steppers, DC and AC. Also, in my humble opinion, well made servo drives, while being more reliable over the long term, also have more going on in the feedback and processing loop so there is a learning curve. You will be introduced to parameters like "following error". In short, servos are more complicated.

Ed

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Re: Stepper vs Servo

Post by kilrabit »

I personally prefer servos.
You do not lose steps from pushing your machine to its limits. Every once in a while you just might.
Servos cost more to buy, replace, and maintain, over the life of the machine, I have some machines 23 years old and no problems yet.
You are buying new, so you do not have to worry about tuning the servo, the extra wiring, and the extra parts to fit into a box, and the different voltages.
Steppers work fine within their limits, and servos work fine within their limits.
It gives me a peace of mind about accuracy when I get finished with the job, which is one less thing to check when there is a problem,
and nearly always works out to pilot error and not machine or software error.

Roy

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Adrian
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Re: Stepper vs Servo

Post by Adrian »

On my machine I have a halfway house. Closed loop steppers which are basically stepper motors with the ability to detect if they are being pushed too hard (or losing steps for other reasons) so they can correct and not lose steps for the whole job.

They are not as precise as a servo when going over the limit but, for the type of jobs I do with hundreds of parts, if something causes lost steps then the absolute worst case is I lose the part it's cutting rather than everything afterwards as well which is the case with the normal open loop steppers.

garylmast
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Re: Stepper vs Servo

Post by garylmast »

Aussie wrote:
Mon Apr 12, 2021 1:49 am
Time to upgrade my CNC to a larger model, I currently have an Axiom AR6 Pro.
I do have several options on the machine.... Servo will add about $3K what is your opinion ? is it worth the extra dollars?
I have two machines, one with steppers and the larger one with servos. Both have the 6 HP spindles. On the stepper, I've had the manufacture add air cylinders to help on the "Z" because of the heavy spindle motor. An older machine, I added heavy springs. Other than that, I don't see a lot of difference.

Gary

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