Geeetech Rostock 301, current limit setting for all motors

[wushu2266]

Hi all,
Almost finish putting the Rostock 301 together. I think the axis miss steps at certain area of the machine. Can anyone provide the current limit for X/Y/Z motors and extruder motors? Thanks.

[William]

About 1.2A.

[wushu2266]

Thanks William for your quick reply.
X/Y/Z motors are 42SHD0217-24B
The current rating are 1.5A as I found from internet(file attached).
Based on "https://www.pololu.com/product/1182", the calculation for adjusting current limit on A4988, Current Limit = VREF × 2.5. So, I used this formula and adjusted VREF= 0.6V, (VREF= 1.5A/2.5=0.6V). I measured the VREF on A4988 before adjustment, they were ranged from 0.51V to 0.55V. I do not know the current sensing resistor value on the A4988. After VREF = 0.6V setting, I did not hear the motor miss any step, so far so good. I installed the heat sink since now the current limit is higher than 1A.
What VREF value you have set to on your Rostock 301?
I have not done anything on extruder motor yet, I am not there yet. The model number stamped on the motor are 42HSC8402-15B11, but I could find 42HSC8402-25B, the current rating is 1.5A. I could not find the exact model number specification from internet.
Please forward a copy if you do have the specification on this motor.
Thanks again.

[William]

Hi,
42HSC8402-15B11's specification is the same as 42HSC8402-25B,the last numbers just suggest different batches or factories.
http://www.geeetech.com/hybrid-stepper- ... p-947.html

[wushu2266]

Thanks William for the stepper motor specification.
Can you share what and how to determine the VREF voltage(current limit) on A4988 module for Rostock 301?
Thanks again.

[William]

The default Vref is 0.6V,and we adjust the volt by rotating the little screw on the A4988.

[wushu2266]

Thanks.
VREF = 1.5 /2.5 = 0.6V
Same formula from "https://www.pololu.com/product/1182"

[raoulito9]

Hi.
I had to set stepper voltage to 0.7.
It was originally set to 5.5, and steppers did not have enougt torque and missed some steps.
At 0.7, it is ok, no more steps missed and steppers don't even get warm

[wushu2266]

Hi.
I had to set stepper voltage to 0.7.
It was originally set to 5.5, and steppers did not have enougt torque and missed some steps.
At 0.7, it is ok, no more steps missed and steppers don't even get warm

A4988 can drive up to 2A motor. I would suggest to set the pot for 0.6V if the motor can run without missing step. According to the formula, 0.7V is equal to 1.75A. The rating for the motor is 1.5A, the limit adjustment is to protect the motor. Most of the A4988 that I received from Geeetech were set for about 0.55V as you have. I did have missing steps and not enough holding torque(I heard the motor was pushed out of position when the other two motors moved).

[William]

So did you solve your missing steps by setting it to .6v?