Re: [CAD_CAM_EDM_DRO] BDI with DRO/Encoder Board

David Kryskowski wrote:

> To All:
>
> We have put together a Shoptask El Dorado with Camtronics Servos, Power Supply and DRO board. The servos are being driven by Geko 320's. We have installed the BDI and have been trying to get EMC functioning with smdromod driving the motors. Our initial attempt failed due to erros in smdromod. I have downloaded from sourceforge dro.c, dro.h and extsmdromod.c and compiled them (along with some changes to handle our home and limit switch setup). We can only get X and Y to work. The Z axis does not function properly. It seems like the feedback information from the DRO board is not getting through. When the Z axis is jogged we get and error saying that it can't follow (I can't remember exactly). Any suggestions?

The first thing is to make the encoders work right. You should be able to
move the encoders (motors, leadscrew, etc.) manually and see the numbers
change in the right direction and amount for the movement.

I think you may have a problem with too many cooks in the kitchen!
The gecko 320 takes encoder feedback, and receives step pulses
from the CNC, and moves the motor to keep them in sync.

The smdromod.o ALSO takes encoder counts and issues step pulses,
and will issue additional step pulses when there is a discrepancy.
Now, in the long term view, all these corrections should cancel out,
but in the short term, there may be too much hunting around by two
servo systems that were never designed to work together. maybe
they are already working, it is not completely clear from your message.

When the axes don't move the way the computer expects, you get a
following error message. You can increase the permitted following
error to see if you can visually the what the problem is. but, without
the feedback working, you WILL get a following error, as EMC is not
seeing the motion that apparently is ocurring.

Also, with a servo system, all polarities (direction moved, movement
sensed) must be consistant, or the servos will attempt to correct by
going the wrong way, making the error greater, until a following error
ocurrs. If the system jumps in the Z axis, you may have a direction
polarity wrong.

Jon