[bachlewelding]

Hello all,

I keep having a problen with my Hitachi Mill. The Fanuc 6MB control keeps giving me a " System Error 904" . What does this error mean, and what is the best method of corrective action? I purchased this machine used in March of this year, and have not been able to make chips with it yet.

[Dan Fritz]

You've apparently got some bogus data in your bubble memory, or maybe a problem with the bubble memory board.

If you can get the controller to boot up normally at all, get a good copy of all the parameters now (before its too late). You can manually record all the parameters from 000 to 380 or so, or you can punch them out to a PC using the serial port. If you have a serial connection to a PC, get your PC ready to receive, put the CNC into EDIT mode, press the PARAM key, then key in P-9999 then PUNCH. Once you have all the regular parameters recorded, look to see if you have any "PC parameters". These are displayed by pressing the PARAM key twice (look for "PC parameters" on the top of the screen). Manually record all the Timers, Data tables, and "Keep relays". PC parameters are only used on machines that use the Fanuc programmable controller (PC) to control all the machine interface functions. My guess is that your Hitachi mill uses the Fanuc PC, so be sure to record the PC parameters too. You can't punch the PC parameters to a computer, so you will have to record them manually.

Also, if you need to back up the part programs that are in memory or the tool offset data, this would be the time to do it. Some machines use special "Macro" programs with numbers that start with 9000 for special cycles (like tool changes) so if you have any of these, be sure that they're recorded.

Once all your data is safely recorded, you can then start clearing various sections of the bubble memory and reloading the data. You can first try to clear the part programs by holding the RESET and the DELETE key while turning the control on. If the 904 alarms still happen, try clearing out the parameter data by turning on the parameter Write/Enable switch on the main board, then pressing the red "CAN" key and the DELETE key while turning on the power. (you'll then have to re-load all those parameters). If all that fails, you can try totally clearing the bubble memory by turning on that Parameter Write/Enable switch and holding the letter "O" key and DELETE while turning on the power.

If these memory clear operations fail to stop your 904 alarm, you may have to do a complete "bubble initialize" procedure. This procedure is described in the Fanuc 6T-B and 6M-B mainenance manuals.

In any case, you've got to back up all that data FIRST!

[bachlewelding]

Thanks, Dan. I will give it a shot. Also, do you know where I may be able to get a Manual for the Fanuc Control? All I have is Hitachi manuals.

[bobgerman]

You can go straight to Fanuc for any manual. However, the first thing they'll tell you is that the machine manufacturer is where you should go. And normally this is truely the best thing to do. The machine manufacturer sets the control parameters based on their machine. If the machine manufacturer has a manual available it will normally be much simpler then the Fanuc manual. You have to keep pushing Fanuc and eventually they'll sell you one.

[tomgaasenbeek]

You can probably watch e-Bay and get a Fanuc 6 Maintenance manual as they do come up BTW.

With regards to the 904 - Dan Fritz is right - backup what you can, but I bet you are past that stage as a 904 indicates a hung DMA channel access to the board.

Although we make Bubble Memory Replacements (see us at www.memex.ca), you can reinitialize the "defect loops" sometimes and get the board backup and running.

That said, I like Dan's idea of just booting on and deleting everything (once backed up if possible) is a good first step. Power on holding "0" (that zero) + Delete with the Parameter Write Enable (PWE) switch on (see the lower left hand side of the masterboard). It will come to System Inconsistent page - hit Reset and you will be up with no parameters. Put in the options P0-4 and the NC Params and type in the PC params if present (you have a PC if P3.7 =1 or P3=1xxx xxxx). The PC Timers/Coutners/Keep Relays/Data Tables are at N1001 BTW, then 2001, then 3001 then 4001 - us P number INPUT in MDI mode to enter new values.

The Defect Loop data deal is simply inputing the "bad" loop data in the board. First read them from the silver Hitachi sticker on the protective plate on the BMU. They power up in IPL (holding "-" + "."), put on the Free Mode Enable switch on the top right of the masterboard and then proceed to enter the defect loop data. Do the O+Delete+PWE sequence after. (This procedure is very rare these days and I suspect that new BMU would be a better bet).

Good luck,

Tom Gaasenbeek
Memex Automation Inc.
www.memex.ca

[Leblondmakino]

Always wondered what the BMU Free switch was for on the 6 motherboard!!

John.