The principle of modularity is best explained using Lego building blocks. Countless objects can be created from a few basic building blocks and defined connecting elements. This approach has also become established in industry for products with a much higher degree of complexity and variability: Typical is the platform strategy of the automotive industry, according to which not only engines, transmissions and driving axles, but entire chassis are used as scalable modules for cars of different models, types and even brands. In industrial control and drive technology, too, systems such as PLCs, IPCs, HMIs and drive components can be customized from individual "slices" or several remote I/O blocks for the machine or system to be automated. They can be easily expanded or modified for further use.

It can be argued that the modularization of complex, industrially manufactured products can often only be successful, both technically and economically, because they are built in their thousands or even millions. But can a modularization approach also be successful if, at best, only a few hundred products of one type are built each year?

The answer has to be "yes". There is currently no alternative to modularization in mechanical engineering. According to the VDMA, standardization and modularization are aimed at a portfolio with less variance and complexity as well as an overall lower cost level, without reducing the breadth and individuality of the product range. In order to better understand the significance of this statement, some typical requirements in the manufacturing systems market are listed below.

What the market demands from production

What is required is a high degree of variability in the production systems, which makes it possible to manufacture a wider range of products, even in small to medium quantities. To achieve this, the systems must be scalable and offer options for subsequent expansion in terms of capacity and output. It is not "high-bred" systems for the production of components in large quantities that are in demand, but systems that can be used to flexibly manufacture different products in small to medium quantities.

In the B2B market, it is no longer enough to develop good products, sell them to operators and then wait for service and maintenance orders. TCO models, which were often used in the past to determine the profitability of investments, are increasingly being supplemented by LCC models (Life Cycle Costs). This allows new business concepts including maintenance, service and retrofit services to be offered very transparently. It also makes economic sense for OEMs to turn to benefit and service-oriented models.

For high-priced capital goods in particular, it is often much more economical for the user to expand existing machines or replace individual units or subsystems than to invest in a completely new acquisition. All these requirements can only be reconciled efficiently, both technically and economically, if the production systems are consistently modularized and networked and offered as smart systems in various expansion stages.

Based on experience with Harting customers, OEMs should first answer the following points positively when deciding on the pros and cons of the modular approach:

• The total estimated costs for a new end-to-end modular product group or family will be at most so high that they can plausibly be recovered within the usual time frame and assuming worst-case market development
• The technical challenges of the planned division of the machine or system into individual modules with transitions and interfaces should be assessed as generally feasible by all parties involved
• All operational functions involved in the future service provision process should be prepared to align their working methods with the modular concept of the machines

To what extent should a machine or system be divided into modules and what general approach is recommended? The genius of Lego building blocks lies in the connections between them. These determine the possible granularity of the division, but are also the limiting factor for the connection of components. The same applies to the interfaces of individual modules of a machine or system. The interfaces ensure that a system - a single machine as well as an entire production line - fits together harmoniously and functions perfectly. The core question of modularization is therefore: How do you separate the components of an overall system from one another?

Harting recommends the following procedure for defining the boundaries between the electrical and electromechanical power, signal, data and communication interfaces. First of all, the output system should be organized by function: Key functions that reflect the OEM's core competency; basic functions that span the entire system; and add-on or auxiliary functions. A certain amount of over-engineering in the machine modules, in which the company's own core competencies are bundled, is always an advantage and is therefore also recommended. The functions should then be combined into modules - but only as granularly as necessary.

The parts of the whole

In the next step, the functional relevance for the respective newly defined machine module should be assessed for all elements of the machine that cannot be further divided, such as sensors, actuators, HMI, drives that require electrical power, signal or data connection, and preferably graphically represented and assigned to a corresponding layer in the sense of the automation pyramid. In this process, all interfaces required for the connection of individual elements must be listed and assigned to the respective machine modules. The result is a matrix with all the planned modules of the future system. The hierarchical arrangement of the elements with associated interfaces, including their relevance for the machine modules, is also visible.

The advantage of such an approach is that it provides a basis for assessing feasibility, technical risks and the necessary design of interfaces. In addition, you create transparency for yourself by weighting the importance of the modules for the future system. All the groups involved as well as further specifications and steps for the development of the modules and processes can be derived from the list. The matrix view also helps in deciding to what extent the control of a modular machine or system should be designed centrally or decentrally.