It may have something to do with the amount of " LAG " at a stand still.I've been searching the forums recently looking to see if someone has already posted about the same problem I am having, but I haven't had any luck.
Here's a little background:
I bought a Bridgeport series II back in August. It was hooked up to power, so I fired it up, homed it, ran a simple program, and bought it. I could tell it was originally owned by GM just by looking at all of the asset tags on it.
It has an Allen Bradley 1386 servo drive system on it for the X, Y, & Z axes. The controller is a Heidenhain TNC355. Feedback to the computer is by Heidenhain LS 403 C scales on the X & Y axes, and a ROD 559 rotary encoder for the Z axis.
When I brought the machine back, I hooked it up, taught myself how to conversationally program it, and made a few parts. During that time, I had some issues with a gross positioning error C. With a little time and resetting, this error was an annoyance, but didn't render the machine inoperable.
Now for the real problem:
A few weeks ago, I fired up the machine to start work on a fuel rail for my Audi. I started up the machine and turned on the control. Once the control is on and memory test completed, I press the handwheel button to turn on power to the servo amp boards. The Y axis lurches, the machine shakes, and the control starts flashing "Gross Positioning Error D" or:
- The position deviation from the nominal
position of an axis at standstill is
greater than programmed in machine parameter
- When positioning beyond the target point
programmed the value of the nominal
position is greater than programmed
in machine parameter 169.
I hadn't even had a chance to home it.
I assumed this meant I have a problem with closed loop control with my Y axis somewhere. I did a little testing and found that after the control is on but before the servo amp boards are powered, I can rotate the belts and see linear scale feedback on the X and Y axis, so they're not the problem. I then pulled off the Y axis motor and checked the tachometer; all was good there. I switched the X and Y servo boards and restarted the machine again; it didn't solve the problem either. I checked continuity from the tachometer brushes up to the servo boards and the Ohms were in the single digits.
I am out of ideas as to what is wrong with the machine outside of the controller itself. Is there an Easy way to check if the Differential velocity command input is giving an appropriate voltage(of about 0 volts, I assume)?
Any help would be appreciated. I have quite a few pics of various components that I thought may help. I'll get them loaded in the near future.
Did you recently have to reload the Parameters ?