PLC Capabilities? Which are considered the "best" and why?

[swhite65]

Giddings & Lewis is not marketed like other PLC's. They have historically "gotten in the door" by being able to perform difficult applications. One of there latest products is called a digital MMC. It is a PLC with many of the favored features mentioned in these threads. It uses tag based variables with no predefined image tables. It can do 64 closed loop analog axes at a 2ms clip while scanning an appreciable ladder. The servos are setup in a file then that file is loaded in the main ladder with a one shot. This starts the servo interrupt. There are hundreds of motion functions in the library as well as ASFB's (application specific function blocks) to aid in motion applications. They also offer a wide range of ASFB's for other applications. These are included with the software. Their customer support is the best I have ever encountered. If you are not familiar with G&L, check them out. This controller is not a motion controller with some PLC capabilities. It is a programmable controller with tremendous motion capabilities.

 

[swhite65]

I meant to add to the previous post: Has anyone in the group ever used or run across any G&L controllers? They are in FonduLac, Wisconsin and have been around for many years. They are far better known in the machine tool industry but this is a separate division. Their PLC is referred to as a PiC (programmable industrial controller). The PLC5 or Contrologix equivalent would be their PiC900 series which is rack based with remote racks, etc.. However the processors are much faster with memory structured differently. In an attempt to be competitive with some of the smaller PLC's they came out with the MMC which is a standalone controller. They have an MMC for PC (1/2 pci slot) which can be powered externally so it can survive the BSOD. You would find similarities with Omron and Siemens in the way the software "drives" and looks as it is very free format. It is IEC61131 compliant. As far as declaring your own datatypes, they have structures, arrays of structures, structures of arrays, and arrays of structures of arrays. Everything is programmed under one platform. There are no separate programs written to intelligent modules that reside in a rack.

I am merely saying that this is a very good and capable product that does not get much recognition. I have appreciated the tools offered which has helped me solve some difficult applications (machine to mark registration, for example). If you encounter a difficult motion or high speed application, check them out or even call their technical support.