Modular design, or modularity in design, is a design principle that subdivides a system into smaller parts called modules (such as modular process skids), which can be independently created, modified, replaced, or exchanged with other modules or between different systems.
A modular design can be characterized by functional partitioning into discrete scalable and reusable modules, rigorous use of well-defined modular interfaces, and making use of industry standards for interfaces. In this context modularity is at the component level, and has a single dimension, component slottability. A modular system with this limited modularity is generally known as a platform system that uses modular components. Examples are car platforms or the USB port in computer engineering platforms.
In design theory this is distinct from a modular system which has higher dimensional modularity and degrees of freedom. A modular system design has no distinct lifetime and exhibits flexibility in at least three dimensions. In this respect modular systems are very rare in markets. Mero architectural systems are the closest example to a modular system in terms of hard products in markets. Weapons platforms, especially in aerospace, tend to be modular systems, wherein the airframe is designed to be upgraded multiple times during its lifetime, without the purchase of a completely new system. Modularity is best defined by the dimensions effected or the degrees of freedom in form, cost, or operation.
Modularity offers benefits such as reduction in cost (customization can be limited to a portion of the system, rather than needing an overhaul of the entire system), interoperability, shorter learning time, flexibility in design, non-generationally constrained augmentation or updating (adding new solution by merely plugging in a new module), and exclusion. Modularity in platform systems, offer benefits in returning margins to scale, reduced product development cost, reduced O&M costs, and time to market. Platform systems have enabled the wide use of system design in markets and the ability for product companies to separate the rate of the product cycle from the R&D paths. The biggest drawback with modular systems is the designer or engineer. Most designers are poorly trained in systems analysis and most engineers are poorly trained in design. The design complexity of a modular system is significantly higher than a platform system and requires experts in design and product strategy during the conception phase of system development. That phase must anticipate the directions and levels of flexibility necessary in the system to deliver the modular benefits. Modular systems could be viewed as more complete or holistic design whereas platforms systems are more reductionist, limiting modularity to components. Complete or holistic modular design requires a much higher level of design skill and sophistication than the more common platform system.
Cars, computers, process systems, solar panels, wind turbines, elevators, furniture, looms, railroad signaling systems, telephone exchanges, pipe organs, synthesizers, electric power distribution systems and modular buildings are examples of platform systems using various levels of component modularity. For example, one cannot assemble a solar cube from extant solar components or easily replace the engine on a truck or rearrange a modular housing unit into a different configuration after a few years, as would be the case in a modular system. The only extant examples of modular systems in today’s market are some software systems that have shifted away from versioning into a completely networked paradigm.
Modular design inherently combines the mass production advantages of standardization, since modularity is impossible without some level of standardization, (high volume normally equals low manufacturing costs) with those of customization. The degree of modularity, dimensionally, determines the degree of customization possible. For example, solar panel systems have 2-dimensional modularity which allows adjustment of an array in the x and y dimensions. Further dimensions of modularity would be introduced by making the panel itself and its auxiliary systems modular. Dimensions in modular systems are defined as the effected parameter such as shape or cost or lifecycle. Mero systems have 4-dimensional modularity, x, y, z, and structural load capacity. As can be seen in any modern convention space, the space frame’s extra two dimensions of modularity allows far greater flexibility in form and function than solar’s 2-d modularity. If modularity is properly defined and conceived in the design strategy, modular systems can create significant competitive advantage in markets. A true modular system does not need to rely on product cycles to adapt its functionality to the current market state. Properly designed modular systems also introduce the economic advantage of not carrying dead capacity, increasing the capacity utilization rate and its effect on cost and pricing flexibility.