Grafcet books?

[thoth3g]

I'm wondering if there are any really good books out there for Grafcet.
I'm basically needing to fix or find a problem in an existing program and it's very confusing. The comments are very minimal and there is no documentation. I have a general idea of what is being accomplished with the transition and steps but the C's and T's are all over the place in the program.
I would like to be a proficient user of Grafcet but more importantly in the short term I need to be able to interpret what appears to be a mess. (With so many logical bits wow)
I have seen several posts praising grafcet but at present I can't say that I share the enthusiasm!

 

[iant]

Sorry - I don't Know
However i found a lot of information on google

 

[thoth3g]

Sorry - I don't Know
However i found a lot of information on google

Believe me I've done that. I guess I was hoping for something more reader friendly.

I did find one book. Literally just one.

 

[iant]

try some more advanced google searches
Gracet turtrial
there's a Utube video - and other things

 

[jvdcande]

I'm basically needing to fix or find a problem in an existing program and it's very confusing. The comments are very minimal and there is no documentation. I have a general idea of what is being accomplished with the transition and steps but the C's and T's are all over the place in the program.

It would help if you would tell us what PLC this is about. For example: if you're using Siemens S7, then Grafcet is definitely NOT the term to search for. Siemens calls this SFC or Sequential Function Chart. In the S5 days it was called Graph-5.

I have seen several posts praising grafcet but at present I can't say that I share the enthusiasm!

As with all programming techniques, the programmer might kill the good intentions of the language by abusing it.
If well used Grafcet is a very clear and straight-forward programming technique. If badly used, you might even confuse the most elaborate Grafcet programmer.
And as with all programming, documentation is essential. Bean counters only see the cost of typing in hours of "texts without any added value". They figure "the program will work just as good without comments". And if a maintenance techie needs more time to troubleshoot, it's never because of lack of documentation, but because "those people suck, they're not fit to do the job, they lack training".
Believe me, most of us here have heard that kind of remarks more than enough in our time.

Kind regards,

 

[thoth3g]

It's plc5 (ab). I'm guessing that perhaps they used Grafcet as a methodology as it has all of the abbreviations for steps and transitions but it is in plc5 not a flowchart. (T's S's C's). They're just all over the place and very hard to follow.(without any documentation) The problem that I am chasing is bad enough by itself as it's almost a ghost anyway. Basically it's a board plant and the "wet" board is transferred down a line as it sets and is cut by a knife. After this point the rollers take it down to the end where belts lift and turn on which transfer the board over to continue on. Once in who knows how many times it transfers too soon and destroys the board. It's all based off of timing and a small increment and decrement timer is given as padding to the operator to adjust it north or south based on timing. Every so often it just immediately transfers destroying the board. It seems like maybe a shifting value of some kind that ultimately resets and starts over (I didn't create it just trying to fix it)


There's so much to this type of job it's unbelievable. Anyone that decides that someone is unfit should try and fill the shoes first.

I've found various things from Google. It's not that I am needing to start using this method but basically just needing to understand it thoroughly to come up behind someone. I'll probably just order the one book that i did find which covers several alternate programming structures and languages for PLC's.
It might be that I'm over complicating it too but I'm inclined to agree with jvdcande in this case regarding the abuse of it.

 

[jvdcande]

There's so much to this type of job it's unbelievable. Anyone that decides that someone is unfit should try and fill the shoes first.

Welcome to the wonderful world of the automation techs. I couldn't agree more to this statement. Unfortunately, the ones who make those statements are the really unfit people to do our job.

You (and every automation tech in the world) deserves more than any manager but gets far less. Some years ago our tech department went on strike. The result: about 25K lost per day for the factory. When the managers went away on "team building trip" business went on as usual. The only loss was the money they spent for their trip.

Kind regards,

 

[TurpoUrpo]

As with all its not that black and white. Some people really are unqualified to do the job. Some are not, some are victim of too low cost offering and need to do fast and dirty.

But then, there is bunch of ppl who does not have any clue about even basic datatypes nor differences on memory types (atleast omron, siemens, codesys has overlapping memory), how person like that could do clean and nice program?

Can you paste some code from your program, it might be designed as grafcet and then programmed in ladder. We have one of those ******* programs. It is not good mostly becouse of lack of comments.

ps. S7 sfc is Graph7.

 

[jkerekes]

If it's an AB PLC5, you can go to the liturature library and downlown the manual. I've only encountered SFC on a PLC5 once in the field. A lot more now on ControlLogix. As with any programming language, there are people who can code clearly, structure it well and document it. Others don't or can't.