Stepping motors for gantry CNC machine tools
A stepper motor is an electric motor, unlike a conventional commutator motor, in which current is supplied sequentially to the stator windings, thereby fixing the rotor shaft at a given position.

Advantages of SD
Stepper motors or servo motors are used to move tables and spindles. SDs are cheaper, but cost is not the only advantage. They have many additional advantages that dictate the choice of this type of drive when building gantry machines:

Easy to set up. The success of starting a system with stepper motors depends only on the correct connections and the right choice of drive. Servo motors require additional configuration; they are more difficult to connect and maintain;
Ease of use. For an inexpensive gantry machine, after several years of intense work, the possibility of mechanical jamming cannot be ruled out. In this case, peak loads on the motor will only result in increased missed steps and mismatches; the problem can be solved by restarting the machine. Increasing the load on a weak servomotor will cause the windings to burn out, while a load on a strong servomotor will cause mechanical failure of the drive;
Motors have a high capacity to hold the shaft in a given position. Servomotors are prone to micro-oscillations when the rotor is fixed; the motor rotor is held in an angular position without displacement.
Disadvantages: resonance, inertia, increased noise. The first problem is solved by selecting a drive with resonance suppression. Inertia is a natural disadvantage arising from the motor’s operating principle, but it only becomes apparent during rapid acceleration. Milling and engraving machines are also faced with other tasks – for example, when applying relief images to stone slabs, where the accelerating motion takes up no more than 1% of the time. The noise level is the last parameter to pay attention to in mass production conditions; here the cost of the equipment is more important (we remember that motor drives are cheaper than quiet servomotors).

Selection of SD
The basic technical characteristics of a stepper motor are determined by its dimensions. Basic specifications (nominal phase current, resistance and maximum voltage of the winding, torque) are the same for motors of the same standard size. The differences are determined by two nuances.

The first is the step division. A smaller pitch means smoother motion, but in this case you will need a drive with a higher input frequency, which will cost more. The most common SD increments are 0.9 and 1.8 degrees – these values are sufficient to solve the standard problems posed by portal machines.

The second nuance is the inductance of the motor windings. Manufacturers produce two versions of stepper motors of the same size. Low inductance motors are characterized by higher shaft speeds and lower power consumption. They are suitable for table movement on unloaded gantry machines. High inductance motors are slower but have higher torque. Suitable for controlling spindle movement along the Z-axis and for controlling the fourth coordinate, as they are better at holding the rotor in a stationary position.

A stepper motor is a multi-winding synchronous brushless motor in which a current applied to one of the stator windings causes the rotor to lock. Sequential activation of the motor windings results in discrete angular motion (stepping) of the rotor.