Noobie DNC Cable / Interface/ Software for VF3

Hi all,
Thanks for all your help so far, I've ordered the 1993 VF3 I asked about in the other thread, and I'm trying to get as prepared as I can for its arrival.

Right now I'm wondering about how to feed programs to this VMC from my computer.

The VF3 has 8 megs of memory. My computer is about 4 years old, running XP, 2 gigs of RAM, 10,000 rpm SATA hard drives.

What is a good way to cable up and handle the connection chores ?
Any recommended ready made cables, cable kits, interface card or software I should get?

My budget is straining at the seams from the machine order, but I'd like to understand what a good and recommended setup would be. No floppy drive on the VF3, just the RS232 connector.

Thanks for any help.

One stop shop

A few years ago, I was in the same place you are. Needed to hook up machines for RS232 and didn't have a clue where to start. Did a little research and ended up calling Doug Struthers at Dostek. 888-355-5735. Truly a one stop shop. We bought his software, hardware and cables, for much less than I expected to spend. He is a wizard with this stuff. He talked us through the whole installation on the phone. I still know very little about it, except it works flawlessly, and if we want to change something, a quick phone call get us on our way. We've added several more machines since then and all is still well.

Greg

CNCME:

Our I232 Isolation System would be ideal for you. This provides electrical isolation at both the CNC and the computer, will operate at 115.2 kbaud, and in many applications can work to 4000 ft (much more than in any CNC applications we have encountered). Visit www.beta-a2.com . Most applications fall into the 25 to 400 ft range.

Electrical isolation very greatly reduces data errors from electrical noise generated in the CNC, or external sources. Some HAAS machines with brushless servos, those after about 1996, produce so much noise when the servos are on that it is impossible to transfer any data in either direction. This is so bad that even Xmodem is not a solution. This noise problem is completely solved by our I232 System.

Electrical isolation provides protection of your RS232 components for virtually all normal electrical faults, such as shorting a hot power wire to the machine chassis, or for most lightning induced faults, a direct hit probably not.

At 115.2 kbaud you can expect to transfer better than 500,000 bytes per minute, or about 12 minutes for 6 megabytes.

One program that I have found to be reliable is Cimco Edit 5. Visit www.cimcosoftware.com . This program does not have Xmodem capability.

If your programs are larger than 6 megabytes, then you can break them into smaller programs or use DNC (direct numerical control) often times referred to as "drip feed". Drip feed is a better term because it is not ambiguous, and used in Google will not produce as much clutter as DNC.

If you use Xmodem protocol, which is a low grade error correcting communication method, then thruput is slightly lower than than using Xon/Xoff software handshake. Xmodem is also a type of software handshake, but does not use the Xon/Xoff codes.

Not all communication software provides good thruput with Xmodem. For example at 115.2 kbaud HyperTerminal runs only about 35% of theoretical maximum thruput. Whereas with a DOS program I can send to HAAS at about 90% of theoretical maximum.

Theoretical maximum for XonXoff at 115.2 kbaud using 1 start, 7 data, 1 parity, and 1 stop bits is 115,200/(1+7+1+1) = 115,200/10 = 11,520 characters per second. Xmodem would use 1+8+1 bits per byte the same as Xon/Xoff, but data is transferred in packets so there are additional bytes sent. These are 3+128+1+1 or 133 bytes for each 128 bytes of data. This reduces the maximum possible thruput to 128/133 or 0.9624 times 11,520 = 11,086. But there are additional latency times that add about 10% of the packet time at this baud rate in a DOS system. Many programs running under Windows may have substantially greater latency times.

I have not been able to get any response from others on thruput with Xmodem that are using different programs.

With our I232 System customers are not experiencing data transmission errors from electrical noise between the two RS232 ports. Thus, their thruput is somewhat better with Xon/Xoff than it would be with a DOS Xmodem. However, there can be problems within the CNC that may occur after the RS232 data is received that could be corrected by the Xmodem communication protocol.

How does thruput affect you, and that means baud rate because time to transfer is inversely proportional to baud rate? Either in the time to transfer files, or if you drip feed then the likelyhood for the machine to stutter for lack of data. This stuttering occurs on contour work (mold making) where many short motions are made. In typical mold applications in drip feed 9600 baud will cause stuttering in some portion of the job. Your 6 megabytes of memory may modulate much of this if you first fill the memory, but at 9600 baud it will take about 144 minutes, 2.4 hours, to fill.

In drip mode at 115.2 kbaud on average you will probably be ahead of the machine's use of data and therefore will be be filling the machine memory ahead of its useage by the machine.

.

Also expecting a "vintage" CNC mill with serial connection (Dynapath 20).

Have been considering adding a relatively cheap PC deicated to the machine (stick it in the controller cabinet or it's own box). Then that PC could be used for storage, drip feed, editing,etc. and can be networked to other PCs or even used with USB flash drives for file transfer. It appears others have done the same and PCs that will handle text files are laying around for free or cheap.

in '99 haas rec'd a db25 to db9 cross cable (null modem) , not the straight through,
from radioshack. that's the one i bought and use . it works fine . the difficulty comes
when setting up the dnc software . at the time i had 3 EMachines p-2 , amd- k7 desktop computers running win98-2 and win2k . the 3 computers were fine for everything else , but none would let me configure the serial ports . i tried another , older, win95 era computer which worked fine with the ez-dnc i was using at the time.

i have since used a p-3 gateway laptop w/ win 2k that works well with connect dnc .
it costs $75 , and is pretty simple to use and setup . used it w/ cinci acramatic,haas,
and fanuc 0m.

here:
http://www.connectcnc-dnc.com/


i have heard that usb to serial adaptors don' t work , that new laptops often don't have serial db9 ports , win xp can be trouble when using
serial ports.

I second the betatronics I232 system, I'm using it on all four of my cnc's with outstanding results. No errors, file transfer as fast as your machine can go. Did I mention no errors And great customer support.

Thanks!

Hi all,

Thanks very much for all the info. and helpful pointers to information.

I'm trying to understand a lot of new material -- I think my brain is filling up.

I'll have some more questions soon, just wanted to say Thanks for all the help so far.

tnmgcarbide:

XP Pro works very well with real RS232 ports (non-USB) with the correct software. I have run numerous tests with Cimco Edit and MAX DNC and can get fast and reliable communication with XonXoff or Xmodem at 115.2 kbaud and 200 ft of cable in my current tests.

Whether you have success or not can be very much dependent upon the software being used.

These tests that I am working on are related to thruput efficiency. MAX DNC is very good at 115.2 kbaud and in Xmodem protocol, while HyperTerminal is extremely bad in Xmodem.

.