How do Arduino-based 3D-printers control several stepper motors at the same time?

Question

I have been using an Arduino to control a stepper motor using an A4988 stepper driver.

The driver requires the direction and step signal to move the motor. The most straightforward method is to use a digitalWrite and delay to indicate the stepping. During this delay the Arduino is frozen and is not able to process other commands. I later realized that my 3D-printer also uses an Arduino and analogous stepper drivers to move all the motors at the same time.

How can Arduino-based 3D-printers with a minimum of 4 motors (x, y, z, extruder) control all motors at the same time?

It seems to me the Arduino is just not fast enough to use a delay()-based method to control 3D-printers, and I was under the impression common stepper libraries are based on the delay command.

Answer 1

The delay() function is bad programming practice and it's unfortunate that it is taught to beginners.

  if(condition1) {                    // trigger
    t1 = millis()                     // start time
  }
  if((millis() - t1) > timeDelay1) {  // elapsed time
    // do something
  }

The above code can be expanded to as many timers as you need. The rest of the program can continue to be scanned no matter how long the time delay is.

Answer 2

During this delay the Arduino is frozen

The solution is don't delay if you need to do something.

Only call delay() when you have done all the things that need doing. and only delay the shortest amount you want to wait for the next thing you need to do.