Z axis will not move


#1

After assembling my wilson II and testing all of the movements I noticed the Z axis was not moving. When I dissembled part of the z axis like the screw rods and the aluminum slugs; I turned on the machine to see if the z motors move. I saw they did move. Can anyone give suggestion please.


First time powering own, motors jittery. (video) SOLVED
#2

Turn up the pots for the stepper motor on the stepper motor driver module (A4988 most likely). Start by rotating them a quarter while turned off before retrying.

When there is no load they can move freely, but with a load the resistance is too big and they can not move anymore.


#3

I would recommend following the correct procedure setting the theVrvef on the drivers. Just turning them will be good to test the theory but without knowing what you have set them to, you may be running them way to hot.

Here is a reasonably good guide to follow for the A4988.

If you are using DRV8825. This a very comprehensive explanation google for a shorty one if you like.


#4

I followed the steps to use a metter to measure the voltage what I found was the motors were 0.846 on meter. Ocordiding to the video one of the responders sent said they need to set 0.42. I was wondering did you have motors set at these voltages?


#5

It could be he is only connecting one stepper to one module and as such needs less amperage than you. You are connecting two z-stepper (which can be stronger than his as well) two one module.


#6

If its stronger what is the normal settings of the stepper motors?


#7

What motors do you have and what drivers are they?

See if you can find the motor number and take a pic of the driver chip and I will I can give a number to try. The problem is with all the information on youtube etc no one ever says what the motors are and chips are. But with the spec sheets for each part the you and work out using the formulas provided.


#8


#9


#10

Here are some pictures I hope they help


#11

Ok the motor spec:

NEMA 17 BIPOLAR STEPPER MOTOR, KL17H248-15-4A, 76 oz-in

Specifications:
Shaft: 5mm diameter with flat
Current Per Phase: 1.5A
Holding Torque: 5.5Kg.cm (76 oz-in)
Rated Voltage: 4.2V
NO.of Phase: 2
Step Angle: 1.8° ± 5%
Resistance Per Phase: 2.8Ω± 10%
Inductance Per Phase: 4.8mH± 20%
Insulation Class: Class B
Dielectric Strength: 100Mohm
Operation Temp Range: -20 ~ +40° C

The Stepper looks like a A4988 which has a sensing resistors are Rs=0.05 ohm

To calculate VREF required for a target current: VREF = A x 0.4

A is Current Per Phase: 1.5A and 0.4 is 8 x Rs=0.05 ohm

So VREF = 1.5A x 0.4

VREF = 0.6V measured on the driver between ground and the turnpot.

This is my understanding of how to get the Vref voltage.