Technology | September 13, 2018
Is Standardization in PLC Programming a Good Idea?
All of the elements of the car production process have to work perfectly, because the process is very complicated. Extreme precision and high standards are a real challenge which companies from the automotive industry must face. Moreover, automation tasks must be completed faultlessly too. This is why companies implement standardization. In this article, I will try to show you how automotive companies manage their PLC code.
Standardization in the automotive industry includes almost every aspect of it; however, if we are focusing only on automation, we can distinguish three main fields:
- mechanics – production lines are only built from well-tested mechanical components;
- electrics – electrical diagrams, descriptions of electrical installation, naming, selection of hardware, and installation methods created in accordance with the established scheme;
- programs for robots and PLC controllers – written according to established rules and patterns, using ready-made libraries.
The standardization of software consists of documentation, ready-made libraries (used for programming) and examples of complete projects.
The standard is created by an experienced group of specialists in one place, tested in a pilot factory, and then transferred for use in others. What’s more, software used in the automotive industry is not created completely from scratch, but is more the result of the evolution of production technology as a whole. Thanks to this, it can be found in the nomenclature which came from the previous era, where control was carried out using contactors, to this day.
The standardization of software leads to:
- continuous improvement of the software created;
- outsourcing PLC programming (offline phase) and commissioning phase (online phase) to external companies, which will reduce commissioning costs while maintaining software quality;
- shortening the time needed for PLC programming and commissioning a new production line;
- easy-to-update standard libraries;
- effective removal of errors in programming and propagation of corrections for other installations.
The creation of a standard for software writing would lead to the need to verify the quality of the written code. This is why corporations from the automotive industry have a multi-stage model of verification.
The first stage is the verification of developers. All employees who join the project must have a valid certificate that confirms their knowledge of a specific standard – this applies to both PLC and industrial robot programmers. The certificate is awarded on the basis of successfully passing an exam conducted at company HQ. For example, the exam for the VASS certificate (VW Group) for PLC programmers consists of three sections: general knowledge of the PLC standard, the ability to read electrical diagrams, and the ability to program controllers in accordance with the standard.
After finishing offline programming, the next stage is virtual commissioning. Here the written program has to be tested by the specialists from a particular company. Tests are undertaken in the simulation environment – reflecting the production line – which allows users to verify the functioning of the software. Tests are conducted in accordance with the schedule.
With the software prepared, developers can start online implementation. In addition, the written code is regularly checked too. The procedure is managed by the software coordinator, who coordinates subcontractors and verifies the correctness of the code. The software is tested by means of automated tests (e.g. validation of naming, network topology, etc.) and manual tests performed by specialists.
None of the above stages can be missed. These stages are vital in reaching the so-called milestones often used, for example, as a criterion for accepting payments for subcontractors.
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While many developers think that working according to industry standards kills their creativity and their work becomes boring after some time as a result, if we are looking from the point of view of companies, the implementation of standards brings a number of advantages. Working with standards requires commitment, precision and regularity. Team coordinators and project managers have a particularly responsible role, because they must motivate the team to ensure the high quality of the work produced.
It seems that the standard developed in automotive concerns is difficult for smaller companies to implement. However, it should be remembered that the implementation of even minor standardization can bring benefits. For example, creating the same pattern for HMI visualization will allow for easier employee rotation between positions. The standardization of devices used on the production line will allow for a reduction in the number of spare parts in the warehouse. Examples can be multiplied, but the fact that the implementation of standardization allows companies to be more competitive on the market should be taken into account.