New Machine Build- What to do with a PLC

[blue_luke]

I am an industrial electronic engineer by trade and I am building my first CNC router these days....

25:"Y by 37:"X y Z:8" with not much to brag about really!

This machine is built with a lot of stuff I have been recuperating / scrounging... over the last couple of years.

I will be using MACH3 and I am "ferociously" reading the instruction manuals.

One thing I found is that it lacks inputs, only 4. Not a problem with MACH3, but with the simple fact that the printer parallel port dos not provide more....

So I thought of using a PLC to do monitoring of ....what?

If I can use say 16 inputs and generate a nible from this group of inputs, then MACH 3 could monitor much more inputs at a time.

Provided : 1 out of 16 inputs at a time can be interpreted
: MACH 3 can be be coaxed to interpret a nible instead of four discrete inputs

What you guys would suggest I can do with a PLC in the system?

I can see a vastly more efficient emergency stop circuit with monitoring of guard doors, limit switches circuit loop, etc...

I have at hand a Omron CPM1A and can get up to 40 INs /32 OUTs

What would you suggest?

Luc

[jamesl]

I know nothing about plc's, but you could add another printer port to your computer to get more inputs

[Al_The_Man]

A cleaner way would be to use a PLC on a network if possible.
Plcbus or other maybe?
Al.

[blue_luke]

Originally Posted by jamesl I know nothing about plc's, but you could add another printer port to your computer to get more inputs

A second port gives axises and outputs I don't realy need and only 4 inputs more...

A 4 bit binary output from the PLC is actually one of sixteen input conditions...

Individual limit switches (rellay needed?) much more "intelligent" emergency switch circuit loop, various critical timings of accessories and auxiliary system controls, but I wonder if
-1 is it necessary? or at least usefull?
-2 what would be useful on a router / aluminium milling machine ?

I understand that most people, probably including myself, can go without a PLC and be perfectly happy with the system...
It is just that the bells and whistle department is fully open, and my question is more about what would YOU do if you can add a PLC to your machine...
I have them, cost me nothing! I have the ladder editing software and the cables etc...

Luc

PS: I may end up not using it, I have not figured out the electrical as of yet, and may find that they have no use, MACH3 is formidable program on its own...

[H.O]

Hi Luc,

Actually it's 5 inputs, pins 10, 11, 12, 13 and 15. The second port can be set to use pins 2-9 as inputs as well. That gives you 4 outputs and 13 inputs on the second port.

I have a CUBLOC "PLC" on my mill, it is connected to Mach3 over MODBUS and I use it to interface my control-panel switches (CycleStart, Feedhold feedrate override etc) and to monitor the state of things like servo motor overtemp, spindle VFD OK signal, E-stop etc. I do not depend on the PLC for emergency stop, it just monitors and lets Mach3 know if the system E-stoped because of me hitting the E-stop or becuase of a limit-switch or whatever I have wired in the E-stop loop.

/Henrik.

[blue_luke]

Originally Posted by H.O Hi Luc, Actually it's 5 inputs, pins 10, 11, 12, 13 and 15. The second port can be set to use pins 2-9 as inputs as well. That gives you 4 outputs and 13 inputs on the second port. I have a CUBLOC "PLC" on my mill, it is connected to Mach3 over MODBUS and I use it to interface my control-panel switches (CycleStart, Feedhold feedrate override etc) and to monitor the state of things like servo motor overtemp, spindle VFD OK signal, E-stop etc. I do not depend on the PLC for emergency stop, it just monitors and lets Mach3 know if the system E-stoped because of me hitting the E-stop or becuase of a limit-switch or whatever I have wired in the E-stop loop. /Henrik.

Interesting!
I just checked the config panel in MACH3 and the panel says "only pin 10-13 and 15 are inputs"
I don't see where pin 2-9 can be configured as inputs on port 2.
A second port cost really little and at that point, I wonder if a parallel to USB port would work? Will MACH3 recognize it?
Hmmmm?
Then a piece of vero board and a dozen of opto-couplers is all that is needed.

I still like the idea of a sub-system built with a PLC for the added safety factor it could provide in the system. I have never seen a PLC going bonker with a windows "blue screen"

Also, the PLC I have on hand does not have MODBUS but I did not know that a parallel port could be used for this! Can you elaborate?

Unless I misunderstood you and you implie that some sort of a modbus to PC interface is used, probably to the serial port in this case?

I know its off topic, but since its MY topic! let's go there, I am fairly new here, but known on other forums to slide easily off, especially when it gets mentions about fine cuisine, cheese, wine and beer!!

Luc

[blue_luke]

While looking elsewhere on the 'zone' I came across this PoKeys 55
http://www.cnc4pc.com/Store/osc/prod...roducts_id=214

A very interesting I/O to USB subsystem... and very affordable!
This thing opens up a host of possibilities and is getting me wild!! :P

I'll calm down.... eventually!

[H.O]

Hi Luc,
Yes, on port 1 only pins 10, 11, 12, 13 and 15 can be, and ARE, inputs - that's hardcoded in Mach3 and can't be changed. The same normally goes for port 2 as well unless you activate the 2-9 as input option in the Ports & Pins dialog (see screenshot).

Mach3 can talk MODBUS to external devices either thru a COM-port (RS232 but can be converted to RS422/485 or whatever with the usual converters) or thru TCP/IP no external "dongles/converters/units are needed. Obviously you need a device (PLC, micro-controller or whatever) that 'does' MODBUS.

MODBUS has the benefit of being a standard industrial protocol and many off the shelf PLC's, I/O extenders, VFD's etc has it built in making it fairly easy to interface them to Mach3 - but there is a learning curve, obviously.

The drawback of MODBUS (and the POkeys and other simmilar units) is that it can "only" beused for "slow" inputs like pushbuttons and other non real-time things. Limitswitches, probe input, home switches etc are not appropriate signals to route thru such a device.

There are a couple of MODBUS-enabled units espically catered towards Mach3, Peter Homman MODIO and CNC4PC's M1 serial server are two of them - none of which I've personally used.

The second LPT-port option on the other hand is perfectly usable for as well slow and fast "signals", you can not use an USB printer port dongle though, only "true" parallel-port cards.

/Henrik.

[blue_luke]

Thanks for the clarification H.O.

I know MODBUS, without having ever used it, the machines I maintain are all from Europe and use more commonly the PROFIBUS with Siemens step7 PLC (ST-200 300 and 400).
Those machines makes cigarette tubes.... Lots of'em!! (6K/minute!!) and are the size of a city bus!

The servo motors are either controlled by an I/O module or directly on profibus, depending of the generation...

I understand also your concern about latency (reaction time) to a command using the USB or Modbus interface...
I guess a mixture of PoKeys and a second printer port is all that I could ever need then....
This is VERY interesting indeed
Thanks, Luc