Difference between servo and stepper motors in CNC router

Stepper motors have high torque to hold position but AC servo motors have much faster travel speed as well as high torque. Also with feedback loop servo motors keep accurate position within 5thou. In this example, both machines are running at full speed. Servo CNC on the right travels 2500 inches per minute with 50 in/sec2 acceleration while stepper runs at 900 inches per minute max speed without stalling at 20 in/sec2 acceleration

[Foxfried]

Wow they machined the air perfectly, looks identical on both devices!

[revtmyers]

So glad to come across this actual side by side comparison. This definitely helps out in seeing the value of the additional costs for servo.

[ctorok]

There is one thing everyone seems to forget. It is nice to see the machine moving fast when not cutting. But they will both do the exact same when they do. The main advantage of servos are torque and precision. They got higher torque than steppers and they got a feedback loop so they can’t make a mistake, whereas stepper can skip steps.
Speed only matters when they are in rapid positioning mode before and after cutting.

[Zebra]

These "comparisons often put $1000 AC servos against $50 steppers. Start with comparable budgets and it's a different story.

Both steppers and servos come in a broad range of power, speed and torque. These can be further adjusted with gearing and / or faster balls screws.

In terms of the part you get at the end and machining time, there's often little difference if the motors are sized correctly and CAM settings are correct.

This decision is usually made by the budget.

[curiosityguy]

Wow, this video is so powerful in convincing about the difference. It seemed to take forever for the step motor to finish after the servo stopped moving.

[hectorae]

except of course in 90% of all cases your spindle isn't going to cut the material fast enough to warrant the extra servo motor speed.

The accuracy of the servo's to me is a much more important factor.

[dannyyu]

That sounds really really stepper, but can feel that installation is good. 😀

[MCircuits]

And of course, the price difference between those two exact machine with different electronics is huge. Am I right?

[vanish]

Notable is the difference between
The machine on the left runs at a constant speed, while the machine on the right is highly responsive during stop-acceleration.
This enables high-speed movement between points and reduces unnecessary time consumption between the work point and the next work point.
Of course, the machine on the left, moving at constant speed, can expect excellent precision.

[jacoweber]

servos are great but 10 times the cost

[horiavilceanu]

Which one is running faster on the highway, a Jeep (50 k car) or a Ferrari (100 + k) ? Of course is gonna be the Ferrari. By how much ? Well, it depends on the length of the highway; the longer the highhway, the bigger the time difference between the two . Will this speed difference stay the same when actual milling things ? Hardly. Indeed, hole making is one particular application where the time difference stands out. Any other type of operations ? (facing, contouring, pocketing, etc) Not really. Is it worth the upgrade ? It really depends on the type of work and how fast the management is able to take orders in a year; if 2 months are really busy and 10 months are rather "relaxed", it probably wouldn't justify the effort. In reality when milling, the time difference should not be more than 10-15 %, bearing in mind that it is not a fully automated job and setup time is the same for both servo and stepper motors. There are many operations where milling is 20% and work setup is 80% of the time. Too many sometimes.

[satyendrashrivastava]

thank you i m going to purchase CNC, ,,differnce between steper and servo

[iedgi]

These servos appear to be suffering from a voltage issue. The gantry is having trouble launching off of the table and through the wall behind them. I suggest switching to solid state rocket boosters for additional torque.

[powerpc]

Since this test only uses the free-running state of the machine (to reposition the milling bit in fact between milling positions) and you should use fixed milling speeds for a specific material and milling bit, the end-result could be negligable when your mill is constantly being used, or am I wrong? I saw some videos where they calculate the proper feeds and speeds for a given bit and material so if the bit is being used 100% of the time, the speed difference can be ignored when the machine isn't using high-speed to move to a different position to start milling elsewhere in the work-piece. You could optimize the pathing in the software to use a minimum of high-speed repositioning instructions, then it shouldn't make a big difference. I could be wrong since I don't have a CNC machine yet, but I'm considering to build one myself using Nema23 steppers (3Nm holding force) for milling wood. And since my budget is limited, I don't think I have much choice (at least to start with) to start using steppers instead of servos.

[Azmodan]

at the beginning you can see that 2 different gcode machines make different movements so what's the point of comparing it. The Servo first goes straight backwards on one axis and the stepmotor goes diagonally. I have no doubts that the servo is faster, but I'd rather see the same movements and the real difference in time.

[tcurdt]

Unless the software driving the machine is super smart and knows the acceleration curve - does it really matter? IRL it probably has to be a linear curve to sync the two axis when cutting anyway. No? Or what am I missing?

[mapache_jega]

Hola. Gracias por compartir. Que marca de servos es ? Que marca de closed loop steper es?

[FrostedImages]

Does the same apply for Hybrid ( Closed loop) Stepper motors? I run the Leadshine Easy Servo aka Hybrid Stepper on my machine. Very nice side by side comparison.

[andreya]

This is an idle move. Which takes up little on average. In real work, the indicators will be different.

[FrostedImages]

Care to explain how the time is one minute apart, when the feedrate and acceleration speed are 50% within each other?