What is a PMC?

sinha_nsit

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Aug 2007
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varanasi
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It is "programmable motion control" which is used in a CNC machine. If motion control is done by PMC, what is the role of CNC control. I understand that M codes are implemented by a PLC. Or, does the PMC do everything? If so, it should be named a PMC machine, rather than a CNC machine. Can somebody show a block diagram of the control aspect of a CNC machine. I was under the impression that CNC control is a sophisticated control for accurate tool motion, for which a PLC is not adequate. What does what in a CNC machine?
 
It is a Programmable Machine Control logic in a GE Fanuc CNC controller.
It is generally a ladder logic program sometimes written with Proficy Machine Edition software for the I/O and auxilary axis in a typical CNC Controller from GE Fanuc.
It can be thought of as the "PLC" part of a "CNC".
 
Sorry for the stupid question, but I really want to clear my confusion. Please correct my interpretation:

In a CNC machine, all tool movements and auxiliary machine functions (such as door open/close, spindle start/stop etc) are accomplished by a PMC. The CNC provides a means to control tool movement by the PMC through the user-friendly G-codes, many of which are complex canned cycles. So, CNC is a kind of programming interface between the user and the PMC. CNC interprets a program and gives appropriate signals to the PMC. It is the PMC which runs the machine through servo motors, pneumatic/hydraulic cylinders etc. PMC is a hardware; CNC is a software program for controlling the CNC machine through its PMC.
 
I have a customer that has a router, it is controlled by a fanuc controller with 3 servo amps, about 15 years old. is it possible to connect to it and troubleshoot issues like sudden faults that are hard to find. I am familiar with many types of plcs and programming. what software would I need. I have an old version - 4.0 cimplicity
 
Do you have any more details about the controller? Perhaps some pictures.
Fifteen years ago there was still a joint venture called GE Fanuc. GE PLCs were capable of being the controllers for some of the Fanuc servo motors and amplifiers. At the same there were GE Fanuc CNC controllers that worked with the same motors and amps. If your customer's motion control was PLC-based you can use Proficy Machine Edition, which was originally called Cimplicity Machine Edition, not to be confused with Cimplicity HMI/SCADA software.
 
Programmable machine control (PMC) .
Sinha, you are mostly correct in you description. You use fanuc ladder to program the PMC.
The CNC is responsible for motion control, program execution through the part program, and interface to the PMC.
Example: part program line: G0X10.0Y0Z0; in the "CNC"
This moves in a rapid move X to position 10, Y to position 0, (Home) Z to position 0 (home).
To start this you have to be in MDI mode. A semi auto mode, signal in the PMC. Press cycle start-a signal in the PMC. X INPUT, but then you connect that after whatever other interlocks you would normally have in that rung section, no alarms, no overtravels, ectect. To a G bit. For instance G7.2 may be cycle start to the CNC. G8.0 may be Estop Ok. G130.0-130.4 may be axis 1-4 servo interlock. You are constantly within the PMC (ladder) interfacing with the CNC and part program through G-and F codes. F signals maybe F3.1 in auto mode.
You program motion moves in the PMC and CNC. You can have CNC or PMC controlled axis same for spindles. All parameters and servos setup is held withing the CNC memory not the drives. Unless you have a older system with stand alone drives and spindles. You tune the servos and such with other software and within parameter sets in the CNC interface.

And many more..
Hope this helps.
Sorry for being kind of vague, I typed this quickly.
 
Last edited:
Sinha's posting was from 10 years ago... Such is the problem with new posters adding onto Zombie threads, it resurrects and elicits responses to issues that have long been forgotten by the OP.
 

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