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Motor Turning Errors
« on: March 08, 2018, 04:44:18 PM »
I have my X and Y axis both set to 400 ipm speed with an acceleration of 5. 

My X axis is ~2200 steps / inch
My Y axis is ~ 560 steps / inch

The motor turning chart for these two is very different, although they set for the same velocity and acceleration and only differ with the number of steps per inch.

When I run them, the Y runs faster and accelerates faster the the X.

Also I've noticed, if I jog the Y axis, then quickly jog the X axis, the X axis will run almost 4x faster.

Why would the steps per inch (which is correct) change the velocity and acceleration of the axis?

Is this a bug in the system?

When I make a change to the velocity or acceleration in the motor turning section I feels like nothing changed.  I hit the save axis before changing axis or exiting, and the changes are there when I open the screen again.

Anyone else see these problems?
Re: Motor Turning Errors
« Reply #1 on: March 08, 2018, 05:37:51 PM »
The best way to make sure that the settings have been applied it to exit Mach completely. Not sure of the other answeres.

We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.
Re: Motor Turning Errors
« Reply #2 on: March 08, 2018, 06:57:08 PM »

Is this a bug in the system?
Given the thousands of Mach users a bug of this description would stick out like a sore thumb, I doubt therefore
that there is a fault.

When Mach makes a corordinated move the axes move at velocities such that the slowest moving axis can keep up.
If you had a slow Y axis say then could expect the X axis to slow in sympathy so that they can remain coordinated.

May I suggest some experiments:

1) MDI G0 X200
          X0    will cause X axis to move backwards and forwards at the max traverse rate on your motor tuning page
             modified by any rapid rate override that may be in operation.
2) MDI G0 Y200
          Y0....etc Repeats the experiment with the Y axis.

Do the axes move at the same max speed when moved independently?

3) MDI G0 X200 Y200

Did the axes move the same distance in the same time (coordinated) and did the controlled point move at 45 degrees?

'I enjoy sex at 73.....I live at 71 so its not too far to walk.'
Re: Motor Turning Errors
« Reply #3 on: March 16, 2018, 03:14:03 PM »
G0 commands work as expected.

Seems my problem is with the Jogging.

X axis jogs ok.

Y axis

When set with 400 unit/min velocity and 2 unit/min acceleration will job at almost 1600 unit/min
When I change the acceleration to 5 it will jog at clost to 800 unit/min.
When I change the acceleration to 10 or higher, it will job at 400 unit/min.
Re: Motor Turning Errors
« Reply #4 on: March 17, 2018, 02:27:15 AM »
well I can't think of anything that would cause that mix of symptoms.

If the X axis jogs OK the surely so should the Y axis.

I will think about it some more, I hope someone else can chime in with a solution or even an explanation, its got me stumped.

'I enjoy sex at 73.....I live at 71 so its not too far to walk.'

Offline RICH

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Re: Motor Turning Errors
« Reply #5 on: March 17, 2018, 07:19:24 AM »
I have attached the motor tuning profiles for the X axis and three profiles of the Y axes as you have
 described. Take a close look at the profiles. There will be a difference in how fast the y axis (as
compared to the X axis) will actualy move depending on the distance traveled. The profiles show the
ramp up and down ( accel and decel ) and max velcocity relative to a time frame. Notice that for  a
Y accel of 2 and 10 that the time is different as compared to a vlaue of 5.

The max velocity is the same for all four profiles but notice the time required to reach max velocity.
As accel changes the time increases or decreases to ramp up  / ramp down to / from max velocity.
Now depending on distance the axis is called to move,it  takes time to get to the max velocity, you may
never reach max velocity if the distance is short thus your accelerating only and not achieving a constant

A G0 commmand is a rapid move at max velocity and you will not see a diffenrence  for accel of 5.
In a coordinated move the slowest axis defines the velocity. The kernal speed limits how manny
pulses / steps can be sent to the drive.

Make note that acelleration is a change in velocity in time. The profiles show the differences in time
and that relates to distance.

When you jog you can set the jogging rate so be carefull relative to a G0 commnad.

Frankly forget all the above BS and just tune the axes such that the steps per unit are correct and
velocity and accel values are refined for each axis such that the axis movement is reliable and allows for
some head room ( ie; torque required to machine).