Created Date: January 30,2020

Created by: mshonkwiler

I have a system put together using a BX-DM1E-36ED23 PLC (with BX-HSIO2 expansion), STP-MTR-23055 stepper motors, and STP-DRV-6575 drives. In all the PLC controls eight motors, four of which are installed on a 3 axis CNC set up. Two of the motors on the CNC set up are used to drive the same axis, one on either side of a gantry. They 're running off of the same power source and HSIO module and are programmed to run in sync using AXFOLLOW.

The current program I'm running allows me to enter stepper positions on a C-more touch panel, and move all motors/actuators to those positions. This brings me to my first issue - occasionally one of the drives will get stuck in execute mode (smart-position) as if its moving, but never passing or failing. My best guess here is that the move I asked it to make was too small for the given velocity/acceleration I configured it with. Any thoughts on this are welcome, however, that's not my main issue.

Here's where things get funky. When, one of those move commands would get stuck in "smart-position " mode without moving, I would stop the program all together and restart it. The very first thing the program does is run through a sequence of AXHOME commands to zero out all the axis. Basically I send all steppers a full rotation away from the home limit switch, then initiate the AXHOME commands in a specific order. When doing this home search after the failure described, all of the sudden the master/slave motors that were just running perfectly together will get out of sync at the very end of the home search. The first move away from the limit switch works just fine; then at the end of the AXHOME command when the master hit its limit switch, the slave shoots off in the other direction a few rotations making the gantry up to a half inch out of square.

HELP!

Created Date: January 30,2020

Created by: EGoethe

Hi mshonkwiler :

I have used a similar setting as yours. I mean BRX with an XYZ with Gantry.

I found not so easy trying to correct/align the second Gantry axis during Homing and didn't want to risk the mechanics.

I came to the conclusion that Homing for the Gantry axis is complicated with AXFOLLOW.

Instead I tried a simpler way. I decided to wire the second axis in series (same signal) as the first.

In this case I handle only one Axis from the PLC for the Gantry.

Not sure if help

Created Date: January 31,2020

Created by: mshonkwiler

EGoethe

Turned out to be a misunderstanding about how the follower function worked. You 're right the AXFOLLOW is a little tricky if you don't fully understand each options function. When the both axis are configured on our first scan the position was set to zero. Thus when the master axis did its home search and made the value of this new position to zero, the slave axis was shooting back out toward the zero it started with. We changed the settings so the master wouldn't change its position value on the home search, then after homing was complete we turned the follower function off and zeroed both axis. Once both were zero, we turned AXFOLLOW back on. Works perfectly.