Stepper A4988 issues

I am trying to learn about running steppers but it's been quite frustrating.

I have used various sketches and some work better than others, but the main thing I notice is a lack of torque. A DC gear motor has way more torque...I can easily stop a stepper with my finger. I would think that if steppers are used in CNC they'd have plenty of torque.

Is an A4988 equivalent to an Easy Stepper? Should I use a bridge? I'm sorry if this post is not specific, but it would be quite difficult to list all the sketches and issues I've had. It just seems like it's hard to get consistent results and I run into one problem or anther. DC motors are so much easier...but i see steppers in so many applications and they seem to work very well.

Can you post a data sheet for the stepper motor that you are using? Have you set the motor current limit on the A4988 as described in this Pololu page?
What are the motor power supply specs?

Have a look at Stepper Motor Basics and this Simple Stepper Code

An A4988 is a stepper driver chip made by Allegro. It is used in the BigEasydriver board and in the Pololu A4988 board. However the two boards are not identical. For example the BigEasydriver defaults to microstepping and the Pololu A4988 defaults to single-stepping.

...R

stevex:
I am trying to learn about running steppers but it's been quite frustrating.

I have used various sketches and some work better than others, but the main thing I notice is a lack of torque. A DC gear motor has way more torque...I can easily stop a stepper with my finger. I would think that if steppers are used in CNC they'd have plenty of torque.

Is an A4988 equivalent to an Easy Stepper? Should I use a bridge? I'm sorry if this post is not specific, but it would be quite difficult to list all the sketches and issues I've had. It just seems like it's hard to get consistent results and I run into one problem or anther. DC motors are so much easier...but i see steppers in so many applications and they seem to work very well.

Any gear motor is going to have more torque! A geared stepper motor would have lots of torque of course.
For any ungeared electric motor the torque is determined mainly by the volume of the rotor, so NEMA17
motors for instance go up to about 0.4Nm static (pull-out) torque (but dynamic torque is less always for a stepper)

Steppers have issues with resonance, and its vital to understand when you have resonance issues because
it severely affects the performance of the motor. Using full steps is the worst possible way to drive a
stepper as it guarantees maximum amplitude at resonance, and it also very noisy. If the mechanical load
has no damping resonance will more of an issue (belt drives are heavily damped compared to lead-screw for
instance). A stepper motor without any load is going to misstep due to resonance really easily.

My advice is always use some degree of microstepping, say x4 or x8 or so, in the first instance, and
don't tune the top speed and acceleration without the actual mechanical load attached.

Most modern steppers are low impedance windings, these need a current-controlling driver, aka chopper
driver, which supplies constant current drive, not constant voltage like a pair of plain h-bridges.

With a chopper driver the higher the supply voltage the less the torque falls off with spindle speed, but with
steppers torque always falls off with speed, its a fact of life - often datasheets have a set of graphs of
dynamic torque v. speed for a range of supply voltages and conditions.

Unless you have a tiny tiny motor you must ramp the step rate up, like the AccelStepper library does, or
you will stall the motor trying to jump instantly to top speed.