Determining Angular Scale - Help w/ Microsteps

Hi Friends, 

I am pulling my hair out trying to determine how many steps it take for my angular C axis to make one full revolution. I recently had to redesign the tangential cutting head so while I had it off the machine I wanted to tune it as much as possible with the tools i had available  (scale, min max jog speed, etc) 

So i set out to determine how many steps it would take the motor to rotate the output shaft one full revolution. After a few days of doing what I thought was simple calculations to little to no success I tried to go bottom up. That is, hard coding the number of steps and adjusting based on behavior. this took like 5 minutes to get it pretty close.. However, its not perfect and I'd like it to be close i don't understand why it is the number it is. I don't think i understand the 'Pulse/rev' table on the driver. 

The bottom up number i got for steps per revolution was around 540. 

Current settings:
Pulse/rev (dip switches) 1600
Motor Step Angle 1.8
Pulley Ratio :3.12

No matter how i combine those numbers i cannot seem to get anywhere close to the 540, the number that actually produces somewhat close to a full revolution. 

Any help or explanation is greatly appreciated. My end goal is a precise calculated steps per revolution. 

Ps. i am ignoring that this is a servo motor and capable of closed loop control, not sure if this logic holds but i would like it the be as close to correct as possible then use the PID controls to correct error and not lean on it due to sloppy setup work. 

You mean hybrid servo?

(stepper+encoder)

Unless your belt is magic, it will have a little bit of backlash and likely some slip.

Is this a timing belt, a V-belt, or something else?

Why 1600 steps/rev (1/8th step)?

Enter this in the stepconf? wizard:

Driver microstepping: 8(maybe 4)
Motor steps/rev: 200/pulleyRatio

Measure the pulley ratio with the actual belt for maximum accuracy, not using some measuring tape or something.

Please use rational numbers (fractions) to express the ratios. Decimals are harder to understand,

Hi Friends, 


- yes its a hybrid stepper, sorry for the misnomer, i've attached the data sheet of the motor and the drive.

I am using a GT2 timing belt and timing pulleys i got off amazon. The pulley ratio expressed as a fraction is 37.49/11.99. I just realized i should probably use the number of teeth instead which brings that fraction to 60/20 or 3, but this still doesnt get me to the 540 number any easier. How would one measure the pulley ratio with the actual belt? 

I was hoping that the belt system i designed wouldn't slip THAT much. I only have it rotating one way, as belts are good pullers not so good when it comes to pushing. I mean i even have a custom tensioner in there. I can upload cad photos if necessary.

So because i took the head off to redesign it i haven't put it back up on the machine and reset up the drive, all the numbers i am sharing are coming from the little Arduino script i wrote to test this. 


 

Why the hell would the ratio be 37.49:11.99?

Why not 36:12 (3:1)?

So strange and annoying.

Number of teeth might not work.

Enter this in stepconf:

Driver microstepping: 8(maybe 4)
Motor steps/rev: 600

What voltage is your driver powered with?

What is the drive current set to?

What type of PSU is powering the driver?

Old-school transformer -> rectifier -> capacitor supplies are generally recommended over regulated power supplies.

Try getting some big caps that are rated for more than the supply voltage and soldering them to a proto board and power the driver through the board to see if power supply instability is part of the issue.

Perhaps filtering the power supply will fix, or reduce, the issue.

Low voltage and/or current can lead to lost steps which will cause weird stuff to happen.

Try out 625 for the steps/rev in stepconf.

I currently have it on my test bench with a DC power supply set at 24v. Depending on what is doing it typically is drawing around 0.25A. if i turn the current knobs on the power supply it doesnt increase at all.

I have the switch on the driver set to D which according to the data sheet is 2.8 peak or 2 RMS which is alot more than its pulling. Should i switch this to 0-4 according to the datasheet thats about where my current draw is.


I just tried plugging 625 into the arduino code (its not on the machine yet) and its about 1.125 spins.

Try this:

Set the driver to max current, fewest microsteps (lowest number of steps/rev).

Set the power supply to max voltage (not over 45VDC) and max current.

Try putting the biggest capacitors rated for above the supply current across the power input terminals to filter the power supply.