This Old Mill

The journey of a guy getting an old CNC milling machine up and running in his garage…

Software Connection

Now that this old mill is actually connected to a computer (PC), it’s finally time to swap some data between them.  To see the cable I’m using to facilitate the connection, visit my serial connection page.

Before I get into the details of all of this, I’m reminded of a line from the movie Casablanca that goes, “Louis, I think this is the beginning of a beautiful friendship”.  I know that’s corny, but this old mill and the PC it’s connected to complement each other. mill_available_memory The Allen Bradley 8400MP control (AB control) doesn’t have much program storage capacity.  Mine only has a little over 87kB – see the number next to the “Available” field in the screen shot.  Yeah we’re talking Kilobytes, not megabytes or gigabytes – this is cutting edge 1980’s technology here!  According to some of the AB control documentation, the total amount of program storage space was configurable as purchased, so yours may have more.  Memory was expensive back in the day, so I’m not surprised at how little my AB control has.  If that wasn’t limiting enough, the AB control limits an individual program file to a little over 64Kb regardless of how much space is available.  I’ve included another screen shot of the error that’s shown when you attempt to load a program larger than this limitation.mill_full_memory  Even though there is more than 64kB available, the AB control will still indicate “PROGRAM SPACE FULL”.   This limitation aside, its important to recognize a 64kB program created manually  utilizing the AB control’s available G code blocks, autocycles, and autoroutines can actually be quite long and elaborate (see chapter 13 of the operator’s manual).  However, 64kB isn’t much when creating programs generated by modern Computer Aided Machining (CAM) software.  In my experience so far, most of the programs I’ve generated using Autodesk’s Fusion 360 will not fit into the AB control’s 64kB program size limitation.  The good news is this is no big deal!

Why’s that you say?  Well, the AB control is nice enough to allow programs of any size to be “executed from an external device”, to quote a line from chapter AB8400MP_Bandit IV_operator_manual_rev_F

%d bloggers like this: