[samu]

When i dreep feeding on a fanuc OM i got a 087 alarm (buffer overflow).Program starts, evrething is ok, and i get an alarm 087. It happen anywhere in program. Maybe reducing baud rate can help???

[JDenyer232]

When i dreep feeding on a fanuc OM i got a 087 alarm (buffer overflow).Program starts, evrething is ok, and i get an alarm 087. It happen anywhere in program. Maybe reducing baud rate can help???

Yes you can try reducing the baud rate, what are you running right now? Is this a new problem that just started, or have you drip feed programs before without any issues?

[samu]

I have ever drip feed smaller program without problem but i don't dreep feed very often

[JDenyer232]

I have ever drip feed smaller program without problem but i don't dreep feed very often

Let me guesse this program is larger than ones you have drip fed in the past? If so reduce your baud rate, try 2400 to start and see what happens. Hope this helps.

[samu]

i just try 4800 and program last longer before alarm occurs. i'll try 2400

[JDenyer232]

i just try 4800 and program last longer before alarm occurs. i'll try 2400

2400 will probably work out fine, sounds like the buffer is really small, what model control is this?

[samu]

control is OM-D and 2400 seems to work fine

[JDenyer232]

control is OM-D and 2400 seems to work fine

Great, glad it worked out for you, now go make some parts

[robertox]

i have the same alarm and i don't know what i have to do??? somebody can help me??? i can download one file to my cnc but i can't download other files

[JDenyer232]

i have the same alarm and i don't know what i have to do??? somebody can help me??? i can download one file to my cnc but i can't download other files

What control are you using? What baud rate are you using? Are you drip feeding or just transfering the files into the controls memory? If transfering the files do you have enough memory in the control to accept the files you are trying to transfer? Make sure you have a % sign at the beginning and end of each of your files. I also found that on my control, a Fanuc Oi-Mc that it won't recognize the O in the program, if I name the program O2000 I get this alarm, but if I change it to
:2000 then it reads it just fine, why I have no idea. A good place to start would be to look for differences between the file that can be transfered and the ones that cannot. Hope this helps.

[Dan Fritz]

The alarm 087 happens when the DNC software does not respond fast enough to the Xoff command from the CNC.

When you press CYCLE START on the CNC, it sends an Xon character to the DNC system to start the flow of data. The CNC has a small input buffer, which accumulates these characters, and your machine starts to run the program. Then, when the Fanuc's input buffer is within 10 characters of being full, the it sends an Xoff character (DC3, or ASCII #18). If the DNC software stops within 10 characters, the buffer does not overflow, then the CNC drains the buffer until only a few characters remain. The CNC sends an Xon (DC1, or ASCII #17), and the DNC system resumes sending data again.

The problem comes when the DNC software sends more than 10 characters after receiving an Xoff. Your DNC software may not be performing fast enough, or the DNC software may not be configured to use Xon/Xoff handshaking. You can frequently improve the Xoff response time of the DNC software by changing the setting the FIFO buffer in your Windows COM port configuration. This prevents the Windows COM port from buffering data, which increases the DNC software's response time.

Right-click on "MY COMPUTER" icon and select "Manage"
Click "DEVICE MANAGER", then click the "+" next to "PORTS (COM and LPT)"
Right-click on the COM port you are using (COM1 probably), then click "PROPERTIES"
Click "PORT SETTINGS" tab, then click the "ADVANCED" Button
Move the "Transmit buffer" slider control all the way to the left (low)
Click OK many times to exit all menus
Try your DNC software again.

You should be able to run 4800 or 9600 baud on a Fanuc, provided that the "Stop-bits" setting also matches between the DNC software and the Fanuc parameter setting.

[JDenyer232]

Dan,

Thanks for a more complete explanation of how this works. We had never used DNC prior to a few months ago and I had no idea how to even make it work. Ended up taking me 3 days of trying this and that to get it working properly. I still occasionally get a buffer overflow on large programs but only when I hit the feed hold, so I bet changing the FIFO buffer will fix this.

[hambakahle]

[QUOTE=Dan Fritz;485649]The alarm 087 happens when the DNC software does not respond fast enough to the Xoff command from the CNC......

Hi Dan,

Thanks for your explanations on this thread. I have this problem only when trying to get newer PCs drip feeding to my OM controller. My old and failing 486 and pentium MMX on win 98 work perfectly at 9600 baud. I am trying to get a more modern PC with XP working, and have tried most of the suggestions in this thread.
I am reluctant to decrease the baud rate if at all possible(for surface milling). I have also made up a new cable (for a DB9 pin on PC) according to your diagrams on another thread, but with the same results. I can run a short homing program, but anything longer fails. I am using mcomm from mastercam, which is a Dos based utility. I have found it to be great in the past as it is so quick and easy to use. Do you have any suggestions?

[Dan Fritz]

You are overflowing the serial port buffer on the Fanuc control. If you're using Windows XP, try this:

Right-click on "My Computer" icon and select "Manage"
Select "Device Manager"
Find the entry "Ports (COM and LPT" and click the + sign to see what's listed under it.
Right-click on the COM port you are using (COM1?) and select "Properties"
Click the "Port Settings" tab, then the "Advanced" button.
Find the left/right slider control for the "Transmit buffer" and move it all the way to the LEFT (lowest setting).
Click OK many times to exit all menus and try your DNC link again.

You should be able to run at 9600 baud without getting an alarm 087 if your DNC software is written correctly. Some RS242 devices (like USB-to-serial adapters) make handshaking difficult because their device drivers are not responding fast enough to the Xon/Xoff signals.

Good luck!