Joint 3 Following Error

ok I assume you know the config name that you use to start EMC

if you look in your home folder for emc2/configs/name-of-your-config

We are interested in the file ending in INI can you post the contents of it?
or can you compress the whole config file and post it?

I am not going to have to time to look at it now but maybe someone else will.

Chris M

What sorts of things am I looking for within the file?

Yes, It seems to be the "a" axis that is causing the problem. It speeds up & slows down on a simple rotational cut with no "z or y" movement to contend with.

You could first try running the A axis at a slower speed to see if the problem goes away.
You can try this by using the speed override slider on the display and reduce the speed by say 50%
Or use MDI COMMANDS to move the axis with slower speeds.

The real adjustments you need to make as John and Chris have pointed out is in your .ini file. Find the section for the a axis and edit (reduce) MAX_VELOCITY and or MAX_ACCELERATION save the file and try again.

•FERROR to small
•MIN_FERROR to small
•MAX_VELOCITY to fast
•MAX_ACCELERATION to fast
•BASE_PERIOD set to long
•Backlash added to an axis
Any of the above can cause the RT pulsing to not be able to keep up the requested step rate. This can happen if you didn't run the latency test long enough to get a good number to plug into the Stepconf Wizard or if you set the Maximum Velocity or Maximum Acceleration too high.

If you added backlash you need to increase the STEPGEN_MAXACCEL up to double the MAX_ACCELERATION in the AXIS section of the INI file for each axis you added backlash to. EMC uses "extra acceleration" at a reversal to take up the backlash. Without backlash correction step generator acceleration can be just a few percent above the motion planner acceleration.

Rick G

It speeds up & slows down on a simple rotational cut

Depending on how the acceleration is set that is what you would expect..start slow move up to speed then slow down to stop. That is adjusted in the .ini file and what might need to be changed along with the top speed.

Rick G

I can change speed with the speed override slider. But it slows all movements down. I've tried to lower cutting speed with MDI COMMAND but it does not seem to make any difference. I can change all other speeds. That seems wierd.

I have found MAX_VELOCITY and MAX_ACCELERATION files. I will try changing these to see if anything happens.

What are my FERROR settings? & BASE_PERIOD settings for?

I tried a simple program to test rotational speed
%
G1 A0 F400
G1 A360 F200
%
Speeds up & slows down fine.

Why I can change MDI cutting speed commands from CAM generated program but it doesn't affect speed speed I don't know?
I will play with it some more see what I can find.

Now would be a good time to run the latency test.

Go to applications then cnc then latency test. Let it run a while. You can use that info to find the base period that you can run.

I have found MAX_VELOCITY and MAX_ACCELERATION files. I will try changing these to see if anything happens.

What are my FERROR settings? & BASE_PERIOD settings for?

When you lower the MAX_VELOCITY do it in the A axis section, it will change only the A axis, which is what you want.

If you have a move that moves a X, Y, or Z (linear) axis and the A axis (rotary) at the same time the A axis will try to keep up with the linear axis, so it may in fact be moving at it's maximum speed.

Rick G

Interesting info RIck. I did change my setting on the "A-AXIS", unfortunately, it didn't help. I might have to change XY&Z too. Called Sherline for benchmark settings on A-AXIS. They were not set properly from factory. Never thought to ask about XY&Z axis. Will call tomorrow to see what they need to be.