Intermittent non-movement in one direction

[David Windler]

Hi Jeff,

I have been using the Dave Gatton Sidewinder CNC (built last winter) for a while but have recently been having issues when I jog.

The machine won't go in a particular direction, say X-- but will move X++, this can happen to any of the axis individually or all axis. Sometime it is both directions.

Mach 3 will be showing it moving but I will only hear a slight movement of the stepper motor (like a micro step) and then it won't move. Then when I move it sometimes in another direction it all of a sudden moves in all directions.

I thought it might be my long parallel cable (25 ft) but I got a shorter one (15 ft) but it didn't help. I slowed the acceleration from 4 to 3 - didn't help.

Not sure what I can check next or what might be going on. This happens right away (motors are not hot) and it seem to be getting worse.

Thanks for any help,

Dave.

[Jeff Pollard]

Hi,

  The abs. max. for a parallel port cable should be 10 feet.  Anything longer and the signal can be significantly degraded.
  Try it with a shorter cable (like the one that came with the box, which is 3 feet long) and see what happens.
  Longer cables (like 25 footers, etc.) were usually made for serial connections which operate at much lower speeds)

Jeff

[David Windler]

Good idea Jeff - that started me down looking at some other stuff as well.

I used the shorter cable, had to disconnect the Opto-Isolated Break-out Board (BOB) as I was using the 3 ft parallel cable to connect to it - then everything worked.

Just to make sure I swapped out the 3 ft parallel cable for the 15 ft cable - everything worked.

I connected to the BOB (not powered - all the Mach 3 settings off) - problem occurred right away.

I disconnected all the wiring to the BOB (switches, etc) - didn't help.

I swapped the parallel cables from the Drive Box - didn't help.

Only when disconnecting from the BOB did the problem go away.

Do you know what I should look for on the BOB?

Thanks,

Dave.

[Jeff Pollard]

Hi,

  A possibility would be missing solder on a connection, or broken solder joints. 

Jeff

[David Windler]

I checked all solder joints - all good (at least visually and they were good with continuity).

I thought it might be a ground issue and somehow floating relative to the control box or the CPU.

Connected ground of the BOB to the case of the control box - didn't help.

I connected the USB to the from the CPU to the BOB - everything worked fine. I didn't know that I needed 5V from the CPU and maybe I don't and it just fixed a possible floating ground issue (tied all the grounds together).

Not sure but it works fine now.

Thanks for your help.

Dave.