On Thursday 30 November 2006 12:32, [EMAIL PROTECTED] wrote: > How repeatable is this "last move the wrong way" ?
Last two cams, after I whacked Esc and fed in a manual G0 Z upward, that sucker flat-out tried to kill itself. Also, while fiddling around trying to make it happen so I could figure out what I'd done wrong, that sort of thing would occur. Push PgDn and it goes up, push PgUp and it goes up, too. After a few iterations, it works fine. Of course, getting it to fail like that when I'm watching the port bits on the 'scope is another matter entirely. I'm thinking of lashing up a breakout box so I can watch HALscope, the real 'scope, and the mill at the same time. That would give some indication of what effect a few backwards steps really has. > Until we get to the bottom of this, I suggest removing > the workpiece, fixture, and tool from the machine. It's been cutting air for a while and, in fact, much of this has been done without any connection to the mill at all. Just took me a while to realize what was going on. > However, we are sure it is NOT > the cause of the "move a long distance the wrong way and > hit the clamps" problem. One possibility is that my controller / motors are unduly sensitive to starting out in the wrong direction. You can convince a stepper to spin the wrong way if you torque it enough; it doesn't sound happy, but it'll run the wrong way at least for a while after you spin it up. What may be happening is that the motor gets up enough steam in the wrong direction and loses lock when the direction suddenly flips over. At that point it ramps up in the wrong direction; the fractional stepping torque isn't enough to overcome being in backwards sync with the whole-step poles. Also, I have seen on the real 'scope (but not recorded, so apply a salt shaker here) invalid direction signals lasting for tens to hundreds of milliseconds. That'd be enough to ramp up to speed the wrong way, then go -thunk- when the direction signal flips back the right way. Throw in another blast from my footgun and it might all be the same problem under the covers. Onward... -- Ed ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
