I have been working on a Bridgeport verticle mill for some time; testing my trouble shooting skills. I am failing to make progress. The mill in question is a EZTRAK DX. The issue that has me confounded is as follows:
The machine is controlled by an old, built in, Intel based, IBM compatible PC w/ a special plug in board. This board drives the X and Y axis boards which power the tables via servo motors that are part of the whole system. And it also provides information to the readouts on the display.
Originaly, the machine was giving trouble with the "A" drive, not allowing us to use it for duplication of disks for older computer controlled equiment in the shop. I disassembled the drive control box to get the PC boards, including the mother board, out to be serviced. Upon my attempt to startup the computer since reassembling it, I have a new issue. Incidently, the "A: drive works fine!
The problem that has now surfaced is as follows. The tables (X or Y) cannot be contolled by the computer. The manual "jog" controls on the display panel have no effect. The arrow controls on the computer display also have no effect. The display indicators of table position have no relation to actual place and are in fact stuck in position. When I first started trouble shooting this unit the tables appreared to be locked in position by the motor torque, hard to move. Now, the is no resistance to moveing them when the machine is on. When the buttons that control table "jog" or other commands are pushed.the display is unchanged. In short, there appears to be no communication going on between the computer and the tables. The display gives no indication of table position. As part of my troubleshooting routine, I removed the boards from the PC slots and found that the servo drives went into a very slow runaway, driving the table, clockwise to the stops.
I have talked to several people, but none who are totally familiar with the above machine. Any assistance you may be able to provide will be much appreciated.
If a table drifts, you have lost the position loop. Encoders work on 5VDC from the logic power supply through the mother board, through the bmdc, then to the AXSBOB, out to the motor encoders.
The JOG +/- and such plus the drives ON depends on the 12VDC from the same logic power supply. This also goes to the mother board, through the BMDC, and out to the AXSBOB. No 12VDC out of the BMDC and no Jog etc.
Very common to have the L1 on the BMDC to open and thus 5VDC does not come out. Same for the L2 which protects the 12VDC.
Sometimes the NICAD battery on the mother board leaks and usually destroys the path of the 12VDC thus it never gets to the BMDC.
Hope this helps.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)