Servo's vs steppers

[Denny J]

What is the difference between the two and which is better for woodworking where you will be doing panel processing and also 3d carving? Will one give faster production and greater carving resolution or speed?

[ger21]

Steppers and Servos...

[Denny J]

I did see that thread. And thanks for the link.


Has there been any changes in technology to the steppers recently that has made the difference between them and servo's less of an issue?

I have been told by a salesman that the technology of the steppers is advancing to the point that they have now closed any gaps there were and that servos are fast becoming an outdated technology. I don't know enough about them to know what advances have been made and what directions they are both headed.

On 4X8 OR 5X10 machine with a spindle, would you choose one over the other if you were choosing between a 5hp and 10 hp spindle?

[Mongkol]

Hi Gerry,
I have some questions.
If I build router machine and need to cut and engrave on aluminium or metal surface,Is it possible to make it?
Remark: I use high torque stepping motor on X,Y and Z axis.and spindle power at 1 hp.

Cheers,
Mongkol

[maxmachine]

Originally Posted by Denny J I did see that thread. And thanks for the link. I have been told by a salesman that the technology of the steppers is advancing to the point that they have now closed any gaps there were and that servos are fast becoming an outdated technology.

I think that's a bit far fetched.... all of the really high end equipment including mills, lathes, and routers are still servo driven.

Mark

[NC Cams]

The isssue of stepper versus servo comes down to that of cost - how much it costs to create/construct versus the net performance you're trying to achieve.

The price/performance compromise is hard to quantify as that is often a subjective topic - what suffices for some folks might be TOTALLY inadequate for the next guy.

For a hobby system, you can create/buy a stepper that will surely suffice and do so quite affordably. When you want/need PRO performance (as in speed, accuracy, total perfection), more than likely the use of a servo based system will be required/preferred.

Before a/the flames start, YES you can create a stepper that will do darn good, perhaps perfect work on a hobby budget. However, the top end PRO equipment is more than likely servvo based. When you go to that level of performance and cost, you simply spend the extra money and go for the gusto.,

Only the user can adequtely judge the merit of the compromises needed/involved when making the servo versus stepper decision. Some of the compromises that are associated with either technology are pretty well known and documented in the prior thread. How they affect your ultimate decision will depend on your needs and your budget.

Both technologoies have their benefits and liabilities with cost being the favored reason why steppers are still viable even though servos get more and more affordable.

3D milling of mild steel is possbible with a routher IF care and shallow, gentle cuts are used. HOwever, for any substantial milling, youd would be better off with a VMC over a router - expecially with higher amounts of stock removal are planned..

[wcarrothers1]

I was often confused by the servo vs stepper question..

But my step dad (machine shop owner who had his first cnc back in 1977) only had one thing to convince me to stick with servos reguardless of price..

Went something like "you would have to keep an eye on that machine else it would start lieing to you".. That machine was stepper based.

Personally the extra cost is little to me in order to not be lied to.

Far as price I'm still trying to figure out as I don't think servos are that much more money then steppers. I run my machines (converted round pole mill and 4x8' router mill) from the same controller (switch between them) both machines are servo based.

So if the money is in the controller and you go stepper your next and next and next machine will be stepper.. I'm glad my next next next machine will be servo.

Then factor in the noise.. If that isn't enough to convince anyone (see any youtube cnc video you want with loud drives (think matrox old school printer days)) then you might as well do steppers..

Personally I'd pay just about anything to have a quieter machine.. If steppers were quieter I'd perhaps use them..hehe

b.

[CarbideBob]

I have been told by a salesman that the technology of the steppers is advancing to the point that they have now closed any gaps there were and that servos are fast becoming an outdated technology.

Sometimes when all you sell is hammers everything looks like a nail. Beware of advice from someone who has a horse in the race.

There are good reasons that all the big guys use servos.
Steppers are cheaper and easier to setup. Servos are faster, more accurate, and need much more engineering to get right.

Bob

[Denny J]

Thanks for the input. I think too that what was said in the last few posts makes good sense. Everything has a purpose and i think for my application the servo's better need my needs.

[CNCPROMAN]

The other thing you should know is servo's are closed loop system and won't lie to you while steppers only record the move they are making. If you bump or jam the axes you wouldn't know untill you made your clock. Open loop have to be watched all the time.

[dannystooblue]

I have read a lot about servos and steppers. I have a mill that I have retrofit with servos and it runs great. When I had trouble with the servo drives ( I screwed them up ) I called Mariss at Gecko, he asked why I had picked servos over steppers. I thought it would be an easy answer but it isn't. If you look at the torque curve on each of them you will see that a servos torque is an upward ramp, the lower the rpm the less the torque. This would mean that the slower you move your table the less torque you have, this means you must gear down the motor to screw or use a lot larger servos. I ended up gearing mine on my mill to a ratio of like 4 to 1. The stepper on the other hand has its torque holding up to a given rpm then it drops off. If you keep your motor inside this rpm range then torque is somewhat constant to the table.

Open loop only with steppers? Not really, if you search here on cnczone for closed+loop+stepper you will run across some really interesting reading about EMC2 operating closed loop with steppers. I believe that there was an increase in the amount of power you could utilize from the motor when it was used with an encoder because there was less need to "overkill" when picking a motor/drive combination.

Noise? depends on the machine... on a router I can't hear much with the router motor itself on. The only time it becomes an inconvenience is when jogging without the router running. Vacuums are loud as well, all of these will cover any sound that a stepper might be making.

Danny

[CNCPROMAN]

Servo's cost almost equal to the cost of a stepper with encoder. If you give the right ratio and tune the servo control you will have higher torque. I have used both on machines and find that servo's have been more reliable in the past but technolgy is changing every day.

Any motor that you change the speed, looses torque, even your spindle. It's just knowing the happy medium. Feeds and speeds.

Carl