Servo Motor Vs Stepper Motor: Knowing What’s What When Designing A Machine

beggers February 8, 2018 0
Servo Motor Vs Stepper Motor: Knowing What’s What When Designing A Machine

Each different technology has it’s different benefits to one another, and while this is the case, you still need to figure out which one gives you the best success for your application. That’s why it’s important to weigh out the advantages and disadvantages between the two.

As a machine designer, you shouldn’t just focus your utilisation on how comfortable you feel with a certain piece of technology; you should familiarise yourself with it, and understand it properly so you can make a proper decision entirely based on what is best for you.

So here’s a detailed list of the differences between the two.

Cost

Stepper motors tend to be a lot cheaper than the servos. Although there doesn’t seem to be a specific reason for this because they both have an equal rating of power.

Versatility

Both pieces are very versatile with their use of automation and CNC applications. But steppers are known for their simplicity, which means that they are often found on many different mechanisms such as clocks and printers.

Reliability

The reliability of each technology varies depending on the environment that it is put in, and whether it is properly looked after or not – like anything. Having said that, the stepper has a one up in this category because it does not need an encoder like the servo, meaning it doesn’t have anything that can fail.

Frame Sizes

The servo motors come in many different frame sizes whether that be small or large motors, they vary depending on the size of the machine that they are required to run. While the stepper motors do not have as many choices on the larger scale of things. Although one thing they do have in common is that they can both be found in NEMA standard size.

Setup Complexity

If you have a servo motor, you have to tune them with a closed loop variable circuit if you want to get the right motor function out of it. But the stepper motor only needs the motor wires to be connected to the driver of the motor itself, which is a lot easier as all you are doing is plugging it it.

Motor Life

You have to replace the brushes on the servo motor whenever it has been in operation for 2000 hours. You may also need to replace the encoder too depending on how often this is used. The steppers bearing is the only thing that is being used, so this gives an advantage in terms of its lifespan.

Repeatability

The encoder of the servo motor plays a big part in how well the repeatability is, so you need to make sure that it has been set up properly. The stepper, on the other hand, is constructed in a way that means it doesn’t need any fine-tuning in this department, so has a very good repeatability with no extra help needed.

Efficiency

Servo motors are very efficient motors that are able to yield 80-90% efficiently if it is given light loads to digest. Whereas the stepper consumes a lot of power, which then ends up converting to heat. So their efficiency is around 70%, but this is down to its driver.

Torque to Inertia Ratio    

Servo motors are a lot better at accelerating loads than the stepper. This is because steppers do tend to stall or skip stages once in a while if the motor isn’t as powerful as it needs to be.

Reserve Power and Torque    

Servo motors are able to supply around 200% of power continuously for short periods of time. But steppers don’t have any reserve power so they are unable to do this, although the motors can brake very well.

Resonance and Vibration    

Servo motors make no noise whatsoever; they don’t even vibrate when in use. Steppers, on the other hand, vibrate a little, and make a slight hum when used because of the way the motor operates.

Motor Simplicity    

The servo motors tend to be a little more complex because they are very mechanical and have a lot of internal parts and external encoders to deal with. While the stepper motors have an extremely simple design to go by, with no consumable parts.

Direct Drive Capability    

Servo motors usually need a lot more ratios to gear because of the high RPM that they have. And from this, it makes it very rare to ever see a direct drive setup for the servo. But the stepper motors work perfectly well in the direct drive mode, which is why a lot of people use a motor couple to attach the shaft straight to the ball screw.

Leave A Response »