Help with motor and drivers wiring and setup

[ryghar]

Hello,

Iam building a CNC machine based on OX openbuilds design. The machine size will be 1000x500mm and will mainly work with wood.
I have 4 motors 57BYGH633 and drivers DQ542MA from wantai. You can find motor information in this link http://www.wantmotor.com/product/57bygh.html

This motors has 6 wires.

Researching Iam not sure if wire half coil or full coil...
Please, tell me if Iam wrong with this:

- According to the datasheet the motor has 4 phases and 1.6mH/phase. So, in full coil config, has 3.2mH
- The power supply, according to what I research, may have sqrt(3.2) x 32 = 57v. The driver max voltage is 50v. I can use a 48v power supply with 3A x 4 motors x 2/3 = 8A.
- I plan to set microstepping to 1/8 in a belt driving system with GT2 and 20 tooth pulley. So, in a motor turn I will move 40mm and need 1600 pulses to do that.
My max cutting speed working with wood is 80mm/s. That are 3200pps. In a torque curve I dont see much difference in half coil setup and full coil at that speed. I will use maybe twice of that speed for G0 movements but i dont need torque in that. So, to cut at that speed full coil seems to be adecuate and to cut metals at slow speeds I will have more torque with full coil. I think that for me is the right choice.

Please, correct me if Iam wrong and any suggestion and recomendation will be appreciate.

Thanks!!!

[paulus.v]

Hello Gustavo! Welcome to the forum!

There are three types of connection for a stepper motor, unipolar, bipolar series and bipolar parallel. Nowadays most are wired bipolar parallel because they give best performance. Compared to bipolar parallel, the biplolar series has the same torque but it drops twice as fast at high speed. This gives half the maximum usable speed of a bipolar parallel. The unipolar wiring has the same speed performance as the bipolar parallel but only half the torque to start with. Old motors were wired unipolar as the drivers was easier to build and cheaper.



Unfortunately with 6 wires you are unable to go bipolar parallel.



Paul.


edit: The 50 V drivers are a limiting factor for you regarding speed. Probably you will want to go half coil for better speed even with lower torque. But I'm only guessing as I don't know any details about your CNC build.

[ryghar]

Thank you Paul,

That is my dilema. I dont know the speed (ppm) where the bipolar series drop above unipolar curve. If I can reach 5000mm/min with an aceptable torque, then maybe bipolar series is the best choice (at 48v). If that drop occurs at 500mm/min then is a problem and half coil is the answer.
Do you know the speed where bipolar series start to fail?

And in the case that use half coil configuration, the power supply can be 48v or I have to use 36v? The amp limit config in the driver, is 3A anyway or has to be lower?

[paulus.v]

To make things more clear, with your 6 wire motors and bipolar drivers you have only two possibilities. Bipolar series or half-coil.

With bipolar series you get better torque at very low speeds. It could be useful for a 4th rotating axis for example. Since in bipolar series the rated inductance will increase four times you will need a lot more voltage (than you have) for usable torque at higher speeds.

Since you need some decent speed for your 1 m travel, I think the half-coil is the better choice.

With the voltage you could go up to 20-25 times the rated voltage. If you are using unregulated PSU I would not go that close to the max. 50V.
In half-coil you need 3A and in bipolar series 2.1A. I think the rated current is RMS but I'm not sure.

Paul.

[ryghar]

To make things more clear, with your 6 wire motors and bipolar drivers you have only two possibilities. Bipolar series or half-coil.

With bipolar series you get better torque at very low speeds. It could be useful for a 4th rotating axis for example. Since in bipolar series the rated inductance will increase four times you will need a lot more voltage (than you have) for usable torque at higher speeds.

Since you need some decent speed for your 1 m travel, I think the half-coil is the better choice.

With the voltage you could go up to 20-25 times the rated voltage. If you are using unregulated PSU I would not go that close to the max. 50V.
In half-coil you need 3A and in bipolar series 2.1A. I think the rated current is RMS but I'm not sure.

Paul.

Great Paul, clear like water. I buyed the wrong motors Lol.
Thank you, I will use a regulated power supply and half coil config as you recommend.
I can do the math with that info. I need to know what and why do what im doing.

Good night!