HomeCNC RoutersDifference between servo and stepper motors in CNC router

Difference between servo and stepper motors in CNC router

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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


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  1. 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.

  2. 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?

  3. 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.

  4. 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.

  5. 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.

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