Help solving joint following error?

When I run my router I need to slow my rapids to about 100 in/min (depnding on my ferror value) so that i don't get a joint following error. I am puzzled by this since when i am in the Step Conifuration wizard I can run tests for each axis and run around 480 in/min (8 in/sec) with acceleration values of 100 in/sec². When i originally designed my machine I selected my encoders to make sure I wasn't going to exceed the capability of my computer. So here is my questions...why would step configuration wizard allow me to run faster than I can run an actually program? From much of what I have read the step configuration wizard is a good way to test how fast the machine can run. What am I missing?

Thanks!

I am using Gecko G320 drives with encoders. The Configuration Wizard does allow using the G320 as a driver and bacially it works with the exception of speed (and some problems with my gantry motors).

I tested with FERROR variable. If this variable is low, the "joint follow error appears"
Also some time the motor lost the impulses and due to diffrerence between command value and encoder feedback
value the follow error appears.
If your computer is not fast enough, this error also may appear.
To avoid it I set FERROR = 0.5.
I make the accurate tuning in my lathe and during the programm execution, the FERROR not reached 0.005 mm.
I create custom.xml and display X-ferror and Z-ferror in real time in pyvcp window.
It looks like this
net X.ferror axis.0.f-error pyvcp.ferror

Thanks for the feedback. I checked out the stepper system error documentation and have a hunch that my acceleration values are too high casuing a following error. I tried slowing down the acceleration a few days ago and it didn't seem to help but it is worth another shot.

I will post the results later.