[gateman]

My slave motor on x axis continues to turn the opposite way for a fraction of a second when I reverse direction. In other words, I run the gantry +, stop, then go to reverse and the slave motor continues to go + slightly before it goes the correct direction. Any ideas? I have a project I need to finish today and this is ruining workpieces.

Thanks,
Rod

[ger21]

Has it always done this?

Are you using a parallel port, or motion controller?

In Motor tuning, are all the setting for both motors exactly the same?

[gateman]

It's never done this before. It's been sitting up for a couple of months, fired it up today and it started this. All settings are correct.

[gateman]

Parallel port,mach3, Probotix controller with green motors.

[gateman]

Watch the shaft on motor at top of screen.

http://youtu.be/98B0ZwYMg0k

[CarveOne]

Looks like one side is binding somewhere in the mechanical drive train to me. Are those motors belt drive also? What kind of carriages or linear bearings are you using? I see wood debris on the gantry. Do the problematic axes have built up dust in the bearings?

[gateman]

No binding the motor actually reverses for a fraction of a second. If you turn the controller off you can move the gantry by hand very easily. It binds up only from getting out of square when that motor goes the wrong way.

[gateman]

What's also strange is that it only does it when going from left to right, not the other way around.

[CarveOne]

I suppose that you can prove the motor is reversing by loosening the shaft couplers on both motors and watch what the shafts do with no load on the motors. If one motor shaft lags the other then it is a bad motor or the electrical signals getting to the motor is at fault. Swapping the motors to see if the problem follows the motor would be the next step, but it may be easier to switch the cables (X and A?)at the driver instead.

[gateman]

I swapped the cables, it swapped the prob to other motor so I know it's not the motor. I also removed belts to make sure it does it with no load and it did.

[CarveOne]

Have you tried setting the jog speed to something much slower, like half of what it is now?

If you are using the keyboard arrow keys to reverse the jogs, try another keyboard temporarily. Maybe the keys are sticky from lack of use.

[gateman]

Got it figured out! I have a Cnc mill and my router running of the same pc with a parallel switch to go between the two controllers. I flipped the selector switch back and forth a few times and problem solved! Thanks guys!

[CarveOne]

Good! I was running out of ideas ... It may not have been getting a full logic level signal or a distorted signal from a bad connection in the switch.

[gateman]

I guess so!

[wendtmk]

This may seem like a silly idea, but perhaps you might consider adding a second parallel port if you have the room, and run the other machine off that one. Eliminating the mechanical connection of that switch (which may occur again, possibly in the middle of an operation, never a good thing) would increase the reliability of your system(s), and take that flaky mechanical switch out of the equation.

Mark

[gateman]

It's worked fine for two years like this, just sat up for a while. I'll make a habit of switching it back and forth a few times before starting now.

[wendtmk]

Mechanical switches degrade with age and use. This may be what you are seeing with your switch. I say may, but it also might be there's crud that's gotten to the contact points of your switch. Might be worthwhile to open the switch box, blow out the crud, and clean your switch contacts.

The second parallel port was just an idea to eliminate the mechanical switch from the equation. Once you have each machine running on it's own parallel port, it's only a matter of bringing up the correct configuration of your controller software. Just a thought.

Mark