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Old May 7th, 2012, 06:27 AM   #1
Jieve
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curious about your opinions regarding "common industy practice"

Hello all,

I'm curious of your opinions and experience regarding common industry practice. I am a mech eng with some very basic automation knowledge, and will be taking over beginning and intermediate automation and plc programming courses at the technical school I work for, as the previous instructor left to return to industry. Since most of our equipment is Siemens equipment, i had a one-on-one 3 day training session with a trainer for a local consulting company that specializes in Trainings world-wide for Siemens equipment. We covered what he considered to be the necessary fundamentals for beginning and intermediate courses intensively. In discussing with him certain industry trends and the best way to approach the courses in this regard, he gave me a significantly different perspective than the prior instructor, which led me to ask the experts on this board for your opinions.

Under the previous instructor, the students programmed solely with an older version (5.4) of the step 7 software. Almost all programming done by our students on the mechatronics learning systems (Festo, Amatrol) we have was done in STL. The instructor had worked in industry prior to teaching, between 2001 and 2005 programming mostly automotive assembly lines for Daimler, BMW, Audi and Volkswagen. He claimed most German industry programming was done in STL.

In my 3 day training, we worked almost solely with Tia portal sp2. While the trainer called the Software buggy and said it really should be considered a beta version, even with the latest updates, there were many elements that he pointed out were definite improvements to the older versions. In his opinion, as the students won't be out in industry for another couple years, it makes Sense to focus on the newer software as Siemens will eventually no longer support the older versions of step7. He said, however, that a short intro to the older software may not be a bad idea.

The second thing that I found interesting, was the use of programming languages. As a trainer that does 70% industry trainings and 30% instructor trainings, his opinion was that the vast majority of European industry programs are written in Function Block Diagram so that maintenance can troubleshoot. STL he said is mostly reserved for programming of math calculations, not much more than that. He said programming large systems in STL usually results in maintanence ultimately cursing out the programmer and is overly complicated. For sequential systems with more than 10 steps, he said that s7-graph is excellent for this, using FBD becomes a bit unwieldy and it's easy to start losing the overall view of the program. He also praised SCL a bit for certain applications, but we didnt go into this as time was too short. He said that programming the entire learning systems that we have in STL was somewhat ridiculous and not quite indicative of most industries, and some prior students under the old instructor also said that troubleshooting long programs written in STL was sometimes a disaster.

I'm curious what you guys think about this. I know most of the native English speaking colleages on this board probably mostly program in Ladder, and this is what I learned first and is most intuitive to me, but where I am working this isnt really an option, since we dont use LAD.

So what'cha think?
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Old May 7th, 2012, 07:30 AM   #2
Binaural
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You will find quite a few various answers on this. In my own experience working in Germany, I found that STL to be often used for systems with low complexity where the primary consideration was quickly and easily generating blocks using copy-and-paste techniques. The programs could be quite long, but with little sophistication, so the programmers worked as much out of Excel or Notepad as Simatic Manger. More functionally complex systems were done either in FBD or in ladder. A well-written FBD or LAD state machine should still be pretty readable either way.

If you've got a huge program written in STL to maintain, then you have my sympathy - I hated debugging STL. It's a total grind compared to being able to diagnose problems at a glance with LAD, or even FBD.
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Old May 7th, 2012, 07:31 AM   #3
Doug_Adam
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My experience with machines shipped in from Germany,
Old = STL only
New = FDB + STL.

I never used the old S5, but people tell me that you really had to use STL to get the most out of it.

For myself, I will use either Ladder, FBD or Structured Text. Occasionally SFC, with IL or STL reserved for only special functions.
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Old May 7th, 2012, 04:09 PM   #4
BobB
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Definately ladder for most things as it is easy to trouble shoot. FB for regular routines only that I use all the time and do not require any trouble shooting but these are rare - mainly for regular floating point maths routines - and that with ST inside sometimes. Never use SFC at all.
Many of my customers have to trouble shoot for me over the phone as they are thousands of kms away - I can walk them through ladder but not the others.
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Old May 7th, 2012, 08:36 PM   #5
Jieve
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Interesting, so that sorta confirms both of what the trainer told me regarding the languages in use now and the take of the previous instructor. In light of this, most of my focus on programming in the course will be focused around FBD, along with a working knowledge of STL on the side. The trainer mentioned that nowadays SCL, similar to C, is becoming much more popular in industry. Anyone have any experience using it?
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Old May 8th, 2012, 01:14 AM   #6
ojz0r
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Quote:
Originally Posted by Jieve View Post
In my 3 day training, we worked almost solely with Tia portal sp2. While the trainer called the Software buggy and said it really should be considered a beta version, even with the latest updates, there were many elements that he pointed out were definite improvements to the older versions. In his opinion, as the students won't be out in industry for another couple years, it makes Sense to focus on the newer software as Siemens will eventually no longer support the older versions of step7. He said, however, that a short intro to the older software may not be a bad idea.
If i held the course i would start with teaching them Step5 and then Step7. That way you learn everything in cronological order and get a larger understanding of the systems development over time.
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Old May 8th, 2012, 03:08 AM   #7
Saffa
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I know it's a tough one, since you've got limited time to teach and you definitely don't want to confuse the students with 5 different languages... but unfortunately, that's what you've got with IEC 61131-3! Since most specs I see these days optimistically call for the PLC to be programmed in an "IEC 61131-3 compliant language", in the futile hope that this would make the program portable to any other platform, I think the students should at least be aware that there are these 5 main "types" of programming language. Maybe even an hour or two spent on the more obscure ones would be useful.

To be honest, I work exclusively in Ladder and FBD. I've not had to use use SFC in a real world PLC (did a few on paper back in university but that was ages ago), and IL and ST are painful in my opinion. I do use something similar to IL for the RTUs we use, and its nasty for troubleshooting.
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Old May 8th, 2012, 04:28 PM   #8
KalleOlsen
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Hi!
In Europe STL(IL) understanding is a must. Your students will be upgrading a lot of S5 code to S7.
And it is the most efficient coding for loop tasks (f.x. CRC calculations).

CFC and SFC in process plants (PCS7 am besten).

LAD or FBD for machines, but if you aren't hunting the last microsecond in speed, I'd allways recommend to use CFC. Mainly because I mean programming is faster, more modern, less chances for typing errors, you get more compact info on one page, it is easier for the maintenance guys to understand and it is redicilous to name and document program internal interconnections (Markers) which one must do in LAD and FBD.

Siemens, the CoDeSys Alliance partners and Bechoff/Twincat (and oscat) have developed good libraries of function(block)s for many different process types, that you can get for a small price/or even free. And it looks very nice parametrized in a CFC environment .

SCL: coming more and more as we oldies fades out, esasiest to transfer between different systems. Nicest looking calculations. I used it on an anti-sway functon for a crane once, started with STL, the customer couldn't cope so I rewrote it to SCL [Damned syntax; ( :=brackets and semicolons.)].

Meine zwei pfennige

Kalle
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