Powerful Stepper Motor Options for Arduino CNC Shield+A4988 RepRap: 17HS13-0404S-PG27 Specs

skosiu wrote:

Hello

What is the most powerful stepper motor that can be connected to the set: Arduino CNC Shield + A4988 RepRap?
The problem is that the engine on the Z axis will operate with a weight of about 3kg.

I don't think this burden is the source of the problem.
So that this weight does not load the engine directly / temporarily, then you can balance the head (whatever is there) with a counterweight (spring system) or a pneumatic cylinder, and then the engine will only be used to move and possibly overcome a relatively small inertia.
Having control: 'Shield + A4988'; you are basically limited to the maximum current set for a motor of not more than 1.0A if A4988 is without a heat sink, or up to 2A with a mounted heat sink and fan, and the maximum operating voltage of motors up to 35V.
The advisability of using a stepper with a gearbox should be discussed. As I understand, the motor is to be used for feed in the Z axis (?), I.e. a lead screw will be used, which often gives a fairly large ratio and protects the self-locking system (with a balanced head weight this problem can be ignored). Multi-threaded screws due to the rather large thread pitch are not self-locking.

Matter of engine selection;
Pay attention to its parameters; If the winding resistance is on the order of 30 ohms and the nominal current is 0.4A, in my opinion this is a bad choice. You won't reach these parameters until the power supply is 12 Volts. Working at this voltage, the engine will be rather slow ('muddy' ; and you don't have too much field (up to 35V) to improve its 'brilliance'. Rather choose a motor with lower resistance and lower voltage; say 1 to 3 ohms and 2 to 3 Volts. Supplying such a 12 V or even 24 V motor; Its current is limited by the potentiometer on the controller, and the 'excess' voltage will increase the speed of interaction, i.e. the possibility of higher revolutions, which you control by controlling / pulsing the A4988 system.
Better results are obtained when using DRV8825 drivers instead of A4988.
e marcus

skosiu wrote:

Can you still tell me what is the formula for the value that I should set on the potentiometer for the following clinic?

It depends on the manufacturer of modules from A4988:
You regulate the original POLOL differently, and their Chinese clones differently. They look the same and have the same pattern; they differ only in the value of the current measuring resistor.
In Polol systems, the value of the reference voltage from the potentiometer is based on the formula V (in Volts) = 0.5 motor current (A), so for 1.5A current setting - you set Vref = 0.75 mV.
For Chinese clones, often called 'stepStick' factor is 1.6; so for 1.5A current one should set Vref = 2.56V
more info here: http://reprap.org/wiki/StepStick

e marcus