HELP! RAMPS 1.4 and bipolar 28byj-48 stepper motor. Steps per rev???

I recently bought a ramps 1.4 with a mega and A4988 stepper motor drivers to build a 3d printer and need to know how many steps per rotation a 28byj-48 stepper motor has for use with marlin firmware. the motors rotate very well but they are not moving to scale. I am using pronterface to program the mega and when I click the test 100mm button the motors rotate very smooth(Already tuned drivers) but less than once. Please help I am new to the ramps 1.4 shield. Thanks in advance.

What made you think that your question has anything to do with the working of this Website and Forum? I have suggested to the Moderator to move it to the Motors and CNC section.

This sort of carelessness makes unnecessary work for the Moderators.

A 28BYJ-48 motor has 2048 steps per revolution of the output shaft. You will also need to allow for backlash in the gearbox.

Unless you have modified the motors they won’t work with an A4988 which is for bipolar motors. The usual driver for the unipolar 28BYJ-48 is the ULN2003 and AFAIK it cannot be controlled with GRBL

…R

This is the first time I have ever made a post in this forum and I didn’t know better my apologies.

I have modified the motors, as I said above, they work fine. But I need to know how to alter the marlin firmware so I can build an effective 3d printer so the motors need to move accordingly. I know some of you people may be thinking “those little motors cannot handle a printer” it has been done and those little suckers are very powerful for their size. it takes a pair of pliers to stop them.

farmboyB: But I need to know how to alter the marlin firmware

I believe I have given you the information you asked for.

...R

would 2048 steps the same for both unipolar and bipolar? Also, would you happen to know how to calculate steps per mm if I were to use GT2 belt and 16 tooth pulleys.(the RepRap calculators don't have any options suitable for my setup) or, should I try to figure out a rough estimate and then simply alter the numbers as I go until they are suitable?

farmboyB: should I try to figure out a rough estimate and then simply alter the numbers as I go until they are suitable?

Yes, definitely.

I reckon you will have to do that with every stepper motor.

...R

I think I've figured it out. Thanks a lot for your help!