RS232 DNC issue on 1997 Haas VF3

[Ensign10]

Hey gents,
Having a bit of a frustrating problem with a DNC feed. This is my first attempt using the DNC function. The computer and the CNC are attached with a 25ft Null modem cable, the computer is an HP XW8400 Workstation with a 9pin to 25 pin adapter coming out the back. The part is a very detailed surfacing operation and the code takes up about 10times as much memory as my machine has. I can't even run a single tool operation without using the DNC function.

So, the DNC seems to communicate fine, but periodically will throw an error mid operation that either shuts off the servos and the spindle, or just the spindle. The latter, of course, snaps off the end mill in tidy fashion. We ran a test part out of wood and thought we had solved these issues. We've tried routing the cable away from any high voltage outputs. Now I'm wondering what further shielding or grounding can be done, or if I should be looking at other issues. We were running a 4800 baud rate when we had success with the wood test piece, but now we cannot get 4800, 9600, or 1200 to continuously drip feed the machine without throwing an error that shuts off the spindle, and sometimes the servos.

Any help is much appreciated.

[Ensign10]

Oh,
We are running Windows 7, programming with Mastercam, and running the DNC with NCnet Lite 7.0. The errors do not happen at any consistent time, or tool path, or operation.

[Kool Parts]

Can you try running a smaller program just to trouble shoot your cable, and other hardware items.
I did this a loooog time ago so I don't remember the specifics but its hard to trouble shoot when the problem is 3 hours into the part.
Gary

[KenFoulks]

How much memory do you have? How big is the program? Do you have the hard drive or extended memory option? Do you have USB? You can also try shielded cabling.

[Pondo]

Had a similar issue caused by the air compressor kicking on during the DNC.
Once the AC was moved to a different circuit it worked fine.

[dcoupar]

This is from the CADEM website:

[Ensign10]

Thank you for all the replies.
I would try a smaller program, but the error doesn't happen consistently, it really only happens several hours in. We actually had it run for about 5 hours on one operation, it only stopped because Windows did an auto update on the computer and restarted the computer.

I have 1MB of memory, no USB, the program is about 20MB, and every single tool operation is in excess of 1MB. So I can't even send it to the machine one tool at a time.

That link from the CADEM site is very helpful, and I'm also looking for a pkace to get some good shielded RS233 cables.

Thank you

[Wizzard of H]

The biggest problem with RS-232 reliability is insuring the machine tool and the PC have a good common grounding system. If the earth ground to either chassis is missing, a big electric motor nearby can cause the chassis voltage on one to be much different than the other. This could be as little as 5 volts to make RS-232 intermittent. Pin 7 in the RS-232 DB-25 wiring at the CNC is supposed to be chassis ground and should go to the chassis of the PC. If not there, you could add it. It's also just as good to make sure a good ground wire runs between the chassis of CNC and chassis of PC.

[Kool Parts]

My cable is 100ft and never had a problem..but just short bursts. I wounder if maybe bringing in a computer to the machine with a 3ft cable might be the ticket.
Also I have a computer that is NEVER hooked to the internet for cad cam, plus some of the worst crashes I have seen are from windows updates. I never let the computer update..ever.

These guys have about every cable there is. They might have some that are better than others, might be worth a call.
Gary

DB25 Male to Female Extension Straight Thru Molded 25 ft

[Ensign10]

Got it figured out...

[Ensign10]

Turns out it was the Program we were running, works great with MasterCam... Thanks for all the input guys