Amount of PLCs

goghie said:

I would never opted for IPC with proprietary software unless I'm planning to close production in 3-4 years.

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+1,
If the said integrator goes out of business and you haven't learn't their propriety software, where does that leave you if you have a problem?

Aardwizz said:

The more stuff that one PLC controls, the longer its scan time. SCADA/HMIs can also affect scan time with lots of data requests.

If very fast reactions are needed (<10ms), then it's best to have several small, quick processors rather than a juggernaut.

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If you're running TwinCAT on a Beckhoff IPC or CX, then scan time "anxiety" is much less of a concern due to the fact that you can control and configure each one of the CPU cores, such as scan time, assigning tasks/programs, etc. It's one of the significant benefits of the Beckhoff platform that integrators/machine builders outside of the Beckoff world don't quite understand or simply don't know about. So having say, an 8-core processor is literally almost the same as having 8 individual PLC processors, each individually configured and running different tasks and different scan rates (or the same scan rates). It allows you to spread the load at your desire across each of the CPU cores. It can all be finely tuned and configured to the application.

If very fast reactions are needed somewhere in the process but not in others, then its not a problem with a multi-core CPU. Configure a 'fast' task for say 50µS scan time and assign it to Core-1, while everything else can run on a 'slow' task at say 10 ms scan time, and assign that task to a different CPU core, etc...etc... Then just assign your programs to the tasks you want to run them.

If you need redundancy and PLC backup, that is not a problem either. There may not be a need to buy multiple PLCs in this case either. In a case such as this, you could simply purchase a duplicate SDD and configure the IPC or CX in a RAID 1 configuration, depending on the level of redundancy you want/need.

Roju said:

Can you argument that please?
Thanks

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Forqnc, explained one important reason. I will try to explain major reasoning.
How much you pay at beginning the machine/plant is just part of the cost, usually smaller one. Also the price of the hardware components is usually smaller part of cost comparing to know-how, except for serial production. The real cost comes afterwards through several factors, like productivity and the fact that you should use your machine in period of 10 to 20 years, etc.
If you find out that later you can be more productive you will need to adapt software and for that you will need not protected software with good support and ability to select the one wich suits you best.
Also what if you need to adapt the machine for new product?
So opting for well renowned producer with accessable software, that you can adapt, is in fact buying a freedom of choice.
PLCs tend to work at least 8-9 years without malfunction, in full production, and it is really easy to change them with same ones. If you select the newest series of PLCs from renowned producer you are opting for having spare parts at least for 10 year in some case even 20 years.
IPCs have several weak points comparing to PLC, to name some:
- operating system, that will, most likely, not be supported in next 4 years;
- usually integrated screen that has very limited lifetime comparing to PLC components;
- PLCs are much more immune to harsh environment. For example, Mitsubishi PLCs that I usually use can work from -20⁰C to 55⁰C without problem in very dusty environment.
If you are investing big money you want to buy certainty that it will make you money.
My advice to my customers is that they ask them selfs questions in following order:
1. Is it safe for people?
2. Is it safe for environment?
3. Is it safe for surrounding equipment?
4. Is it according to all applicable laws?
5. How much it costs?
6. Will it last for enough years to pay initial investment, operational costs, earn me money and earn the money for new machine when times come.
7. Do I have the needed money?

Thank you all for all the advice. Receiving side of the project is something new to me, and with this knowledge it will be much easier to have my input in the process.