UNO + CNC Shield V3 + A4988 Problems

Greetings to the community

I'm a Mechanical engineer and mechatronics new fan, I have been browsing here and looks fabulous this community, its scope and its commitment to help.

I am building my CNC, for that I have selected this hardware and software:

Arduino Uno
CNC Shield V3 (do not know how to recognize the version) was a gift.
Pololu A4988 drivers with sink
4 motors NEMA 17 3.7 V and 1.5 Amp model 42SHD0217-24B
ATX power supply 12V, 35 amp according diagram in the housing
Arduino 1.6.7
GRBL 0.8c
Universal G-Code sender 1.0.9 at 9600 baud, port com5

I followed the instructions for these types of sites for configuration and connection taking care setting voltage reference drivers (0.84 V) and the identification of the coils of the steppers and the final results I have achieved are the following :

Only the X axis works perfectly with torque, speed and accuracy, the Y axis rotates only one way no matter what you do with the connection of the coils and the Z axis buzzes and loses erratically steps but change rotation.

I tried the following:

I tried every driver in the X port of the Shield to rule out any of them are bad, all work well

I tried all the cables from the X port of the Shield to rule out a broken wire, all work well

I tried connecting all steppers in the X port of the Shield to discard bad motors, all work well

I tried swapping the order of connection of the coils in the X port and obey shiels change.

I can conclude that the X port of the Shield is fine because it works well with any combination of other hardware

I did the same procedure with port Y and Z and I got the same fault commented at the beginning, any step motor connected with any wires, any driver A4988 and any combination of coils to the Y port obeys the steps but does not change rotation and any step motor connected with any wires, any driver A4988 and any combination of coils to Z port buzzes and loses erratically steps but change rotation.

All previous changes was made obeying the disconnection of the power supply to the Shield and even disconnecting the USB arduino to avoid shortcuts and damage components.

Is the CNC Shield broke?
What can I do about it?

I appreciate your kind help.

It may help to try each of the motors separately with the first example in this Simple Stepper Code. You will need to figure out which I/O pins carry the step and direction signals for each motor.

...R
Stepper Motor Basics

you must have some kind of firmware uploaded could be in the settings

rogertee:
you must have some kind of firmware uploaded could be in the settings

He said it is GRBL. Have you suggestions for the settings? I don't know GRBL myself.

...R

  1. Your current limit is not set correctly:
    The Pololu site says:

Current Limit = VREF × 2.5

So your set up is: 0.84 x 2.5 = 2.1A (your motors current is max. 1.5A!)
You have to set VREF to 1.5/2.5 = 0.6V.

  1. How did you set microstepping? Imho 1/4 would be ok, more reduces the max. speed, less might be noisy.

  2. Do you have another power supply with at least 20V or up to 30V? The higher the better (watch the voltage limit of the drivers).

  3. Do you have an idea how much torque is required for each axis? Your steppers are normally used in 3D printers; for a normal CNC, depending how it is built, at least the z-Axis motor might be too weak.

  4. How did you test everything? With single G-Code commands to move one axis, then another or how?