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Updated and all links checked: Thu Mar 14 10:53:50 2013

Using Kermit with Cincinnati Press Brake Machines

Cincinnati Incorporated (and other companies such as Milacron, MAG, and many other companies) make press brake machines, used to form or bend metal parts (see video), contour tape laminating machines, tape layering machines, as well as flat-roll, shearing, die-cutting, woodworking, and other types of factory floor machines. The actions of these machines are controlled by Computer Numerical Control (CNC) programs (CLICK HERE for an overview).

In this page we say "press" or "press brake" for convenience, but this can refer to any type of Cincinnati, MAG, or other machine that is controlled in the same way.

Cincinnati machines are connected to PCs via serial port with a null modem cable (explain) (search). The CNC program is written on the PC, downloaded to the machine's controller, and then possibly modified by the machine operator and uploaded back to the PC. Kermit software is used for this process in all machines manufactured since 1987, as you can see in this 2001 handout from Cincinnati Inc. YOU SHOULD READ THIS HANDOUT, and then read the rest of this page for corrections and supplementary information.

The Cincinnati handout discusses both MS-DOS Kermit and Kermit 95, and states that MS-DOS Kermit can be used on Windows 95 and NT. THIS IS NOT NECESSARILY TRUE. MS-DOS Kermit is not designed for, and is not supported on, 32-bit or 64-bit versions of Microsoft Windows such as Windows 95, 98, ME, NT, 2000, XP, Vista, or Windows 7 or 8 (details). If you are using MS-DOS Kermit on 32-bit Windows and have problems with it, you'll need to switch to Kermit 95, which is native, recommended, and supported on 32-bit Windows. This is especially true for Windows XP or later, where MS-DOS Kermit is increasingly unlikely to work at all. CLICK HERE to download a full-featured trial version of Kermit 95.

This page discusses common problems using Kermit 95 with Cincinnati machines. An unusual aspect of the Kermit/press connection is that Kermit is normally in server mode, so it can be controlled by a Kermit client on the press brake; some consequences of this fact are covered below.

I can't make the serial port work

Also see: The Serial Ports and Modems section of the Kermit 95 FAQ.

The newer your PC or Windows version, the less likely it is to have a traditional "COM1" type of serial port (such as an 8250 or 16550A UART with a male DB-9 or DB-25 connector). Newer Windows platforms have all sorts of serial-port and/or modem substitutes or simulations that can't be accessed by the regular COM-port driver, sometimes they have nothing at all and you have search for a third-party USB-to-Serial adapter such as this one. These "non-COM" ports must be used through the Windows Telephony interface (TAPI); that is, through the name listed in the Phone and Modems folder (possibly just Modems, depending on the Windows version) of the Windows Control Panel.

Unfortunately, COM ports (or their modern substitutes) usually do not show up in the Control Panel Phone and Modems folder by default. If this is the case on your Windows PC:

  1. Click Start → Settings → Control Panel
  2. Open the Phone and Modem Options item
  3. Click the Modems tab on top
  4. Click the Add button
  5. When the Wizard appears, click the check box that says "Don't detect my modem..."
  6. Click Next
  7. Under (Standard Modem Types) you should see: Communications cable between two computers listed - select this and then click Next.
  8. Choose the COM port you want to use (COM1), click Next
  9. Once the Wizard completes, click Finish, you should see the new item
  10. Close out of the Phone and Modem options, close Control Panel

Now when setting up Kermit 95, instead of using:

set port com1


set port tapi Communications_cable_between_two_computers

Even when you are using the appropriate driver (COM or TAPI), you still might need to make certain adjustments to communicate successfully:

set speed 9600
(or other speed) Kermit's speed must match that of the press brake.

set flow none
In case your Kermit program is set for RTS/CTS (hardware) flow control, which the press brake does not support.

set carrier-watch off
In case the press brake or your cable does not supply the Carrier Detect signal.

set parity none
In case Kermit has been set to even, odd, mark, or space parity.

Files sent from the press to the PC get the wrong name

When Kermit receives a file that has the same name as an existing file, it normally wants to do something to avoid destroying the existing file. Usually it renames the existing file, and then stores the incoming file under the name it was sent with. For example, suppose a file called HANDLE.CNC exists in the PC's current directory, and then the press brake operator sends back an updated copy of this file. Normally the original copy would be renamed to HANDLE.CNC.~1~ (or HANDLE.CNC.~2~ if HANDLE.CNC.~1~ already existed, etc), and then saves the incoming file as HANDLE.CNC.

But since Kermit is in server mode, deleting or renaming existing files is not allowed by default; that is, unless you tell Kermit it is OK. Thus if you follow the directions in the Cincinnati tip sheet for setting up Kermit and then try to replace a file, Kermit won't allow the original file to be disturbed, and therefore renames the incoming file to HANDLE.CNC.~1~ or whatever.

Kermit's options for filename collisions are chosen with the SET FILE COLLISION command. The default option is BACKUP, but that requires that the existing file be renamed. Another option is OVERWRITE, but that requires that the existing file be deleted. In either case, the server must be told to allow changes to existing files.

If you want to back up existing files:
set file collision backup
enable rename

If you want to overwrite existing files:
set file collision overwrite
enable delete

Execute these commands before entering server mode. Examples:

set flow none
set modem type none
set port 1
set speed 9600
cd /programs
set file collision backup  
enable rename
set flow none
set port tapi Communications_cable_between_two_computers  
set speed 9600
cd /programs
set file collision overwrite    
enable delete

MS-DOS Kermit works with the machine but Kermit 95 doesn't

This scenario has been reported on a Cincinnati Milacron Contour Tape Laminating Machine with Cincinnati Milacron Acramatic 975 Controller.
Kermit 95 calculates packet timeouts dynamically, whereas MS-DOS Kermit uses a (user-specifiable) fixed timeout interval. Here is an initialization (or customization) file that you can use with Kermit 95 that should eliminate the problem. In this example, SET CARRIER-WATCH OFF is included because the serial-port cable only has three wires (i.e. does not present a carrier signal; see this page for information about cables and wires).
SET SPEED 19200 (or other)
SET SEND TIMEOUT 8 FIXED (or other number)
Explanation: When receiving a file, the Cincinnati machine buffers incoming data until the buffer fills up. At this point it “turns around” to write the data out to permanent storage, and this takes significantly longer than the normal packet turnaround. Since the previous packets were acknowledged promptly, K95 had adjusted its timeout to be somewhat lower than the delay that occurs at this point. When the expected acknowledgement did not arrive when expected, K95 retransmitted the previous data packet and evidently this confused the machine (although it shouldn't have). Perhaps when writing data to disk, it can't tolerate activity on the serial port. Anyway, telling K95 to use a somewhat generous fixed timeout cures the problem.

How can I set up a press-brake connection in the Dialer?

The procedure for this is normal, except since most people want Kermit to be in server mode, rather than entering its terminal screen, you should enter the command "server" in the text box of the Login page, along with any desired ENABLE commands for server mode, e.g.:
enable delete
enable rename

Press Brake can't access more than 200 files at a time

A user reports, "I talked with Cincinnati today about the brake only sending 1/3 files through Kermit and they informed me that there is a bug with brakes that have more than 200 files stored on them. When you try a REMOTE DIRECTORY or a GET * it will only bring back up to 200 files. They also informed me that they were not going to fix the bug because there are too many versions of the machine control."

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Kermit and Cincinnati Press Brake / The Kermit Project / kermit@kermitproject.org / 7 July 2004
Updated 26 October 2005, 21 November 2005, 5 October 2010, 12-13 March 2013