[kolias]

I have a similar thread in the machsupport forum and decided to ask here in case someone had a similar problem.

With mach3 we are able to jog the motors with the keyboard arrow and page up/dn keys. For example pressing the up arrow key moves the axis in one direction and pressing the down key modes the axis in the opposite direction.

In my case pressing the up arrow key moves the axis in one direction but if I lift my figure from the key and press it again (the same key) the axis moves in the opposite direction. In other words if I want to jog the axis to the home position I’m unable to do so because every time I lift my finger and press the same key again the axis moves in a different direction.

This happens with all four arrow keys and the page up/dn keys. The direction which the axis will move is unpredictable. The keyboard keys are working fine outside of mach3. The DRO’s are moving in accordance with the key pressed so perhaps this rules out any problem with mach3.

Any ideas?
Nicolas

[ger21]

Try increasing the dir pulse width.

[kolias]

Try increasing the dir pulse width.

Thank you Gerry

That is the Dir Pulse (0-5) in the Motor Tuning Screen?

Mine was set at 5. I change it to other values within the range but did nothing.
Nicolas

[ger21]

You can set it higher. Try 15

[randyf1965]

You should be able to watch the diagnostic page (where all the input/outputs are shown) in Mach3 (not by my CNC machine) and see if the output changes, sounds like something is toggling the dir output.

[ger21]

What kind of drives are you using? Do you have a breakout board?

[kolias]

What kind of drives are you using? Do you have a breakout board?

The motors are Keling 276oz.in with 8 wires and wired as Unipolar. The BOB is Probotix http://www.probotix.com/manuals/PBX-RF_manual.pdf

I did increase the pulse width to 15 but makes no difference. There are no any extra lights in the diagnostic screen.

Setup units is inches and motor tuning is set at about 81 velocity, 9 Accel. and I think that is the best combination but motors are still stalling (some times) and always when they stall the axis reverses.

But also without motor stalling pressing the same arrow key while the axis moves in one direction if I let go pressing and pressing again the same key she will reverse (not always, sometimes and very unpredictable).

Perhaps it is the motor tuning? I started from 10 velocity and 2 accel and increased by 5 the velocity but the happiest setting seems to be what I have. Is there any other way to tune the motors? Any good vel/accel settings?

Approx. Travel is: X=24, Y=30, Z=9 (Z driver board not installed now; was defective and waiting for replacement any day now but switching cable between X & Z, the Z axis does the same with the page up/dn keys)
Nicolas

[ger21]

You need to check if your direction pin is toggling between 0V and 5V when you change directions. Check it at the port, the breakout board, and the drive. Should be 0V in one direction, and 5V the other direction.

[quazga]

Yeah, I'd agree with Gerry.

It's something in the hardware.

In addition to his recommended tests, check your wiring diagrams again. Make sure you don't have a stepper motor wire from the BOB to the driver interchanged with your direction output wire from the BOB to the driver.

That driver direction input is getting an opposite signal every time the motor stops so that could be the problem.

I haven't used Art's software in years, but I loved his software! Art is a genius!

[kolias]

You need to check if your direction pin is toggling between 0V and 5V when you change directions. Check it at the port, the breakout board, and the drive. Should be 0V in one direction, and 5V the other direction.

That is my next step, to check the volts of the direction pin which was also suggested in the machsupport forum.

There is no wiring mistake. I have the BOB and 3 driver boards and the connection between them is thru 3 ribbon cables. I did switch the ribbon cables around just in case one is defective but the same problem persists.

Thru Gerry's input I increased the direction pulse to 15 with no change to the problem but next to this setting there is also the step pulse which was set at 5uS (that is the min recommended setting). So I increased this setting to 10 and the results are fantastic! Both the X & Y axis almost never reverse. I hit the up arrow and as I jog, it keeps going all the way to home and only reversed twice. The X axis seems to be even better.

Due to other work I had to stop my testing but on the weekend I plan to increase this number gradually and see what happens.
Nicolas

[kolias]

Conclusion

I did not mention before but when I received my 3 drives one was defective and had to send it back for exchange.

So I was testing the machine with 2 drives and yesterday I received the new drive and installed it today in the Y axis. The results are fantastic. The axis never reversed without pressing the appropriate key.

Then I installed the same new drive on the X axis and the results again were fantastic.

So my problem was all along due to defective drives which I’m sending back for replacement.

Nicolas