Variant management and modular design for a growing product range

Variant management is about one question: how do you keep track when your product comes in more and more versions? A variant is one version of a product. Think of a bike in red with a basket, or the same bike in blue without one.

Picture this: it's late December, and it's time for the yearly clean-up of the item list. Once again, there are more part numbers than last year. Eighty were added, five were removed. Every customer who wanted something "just slightly different" got a new item. A few of them sold exactly once.

Nobody planned it that way. It happened step by step, one sensible choice at a time. But now the item list is mostly a pile of exceptions. And every item has a drawing, a parts list and a price. Someone has to keep all of them up to date.

Why variants multiply

Variants don't just add up. They multiply. Take a cabinet in four widths and three heights. That's twelve versions already. Add five colours and you have sixty. Add a door option and you're at a hundred and twenty. Every new choice makes the total several times bigger.

That's fine on its own. Customers want choice. Often that's exactly why they buy from you. It only becomes a problem when every variant turns into its own item. Then each one has its own drawing and its own parts list, and you have to keep every one of them up to date.

That's when you see these signs:

• part numbers sold only once or twice;
• items that are almost the same, with a small difference nobody remembers;
• a price change you have to make in dozens of items;
• the production office checking the drawing on every order anyway.

Mass customization in manufacturing

You can give a customer what they want and still work almost as cheaply as series production. That's called mass customization. The idea was made popular by B. Joseph Pine's 1993 book Mass Customization: The New Frontier in Business Competition. Business books usually describe it like this: making goods and services that meet individual customer needs, with an efficiency close to mass production.

The key word is efficiency. It means working without waste. Mass customization doesn't mean anything goes. It means you organise the choices well. That way every version comes from the same building blocks and the same way of working. The customer gets something made for them. The factory does the same thing over and over.

Typical mass customization examples in B2B manufacturing (companies that sell to other companies) look like this:

• modular cabinets and storage systems in a fixed grid, with free choice of finish;
• conveyor lines built from standard sections, drives and supports;
• canopies and enclosures where length and width vary, but profiles and connectors don't;
• machines with a standard frame and a menu of tools and controls.

See also mass customization in the glossary.

Modules and interfaces

The building blocks are called modules. A module is one separate block of your product. Modular design means building a product from blocks you can swap. Think of Lego: every brick fits on every other brick, because the studs are always the same size.

Those fixed connection points are called interfaces. They are the most important part. As long as a module follows the agreed connection, you can swap it. You don't have to touch the rest.

Here are some examples of interfaces:

The stricter the interfaces, the more versions you get from the same number of modules. You also have less to work out again on every order.

Sometimes you have to give something up for this. With a grid, a customer may not be able to pick every millimetre. Or a module is a bit heavier than needed, because it has to fit in several places. So you choose between lots of freedom and easy management. You make that choice product by product.

From bill of materials to rules

A bill of materials, or BOM, is the list of all the parts that go into a product. It's like a shopping list for the factory. In a company without modules, every item has its own BOM. So every variant does too. With modules, that changes. You no longer write down every BOM. You write down the rules the BOM comes from.

A configurable BOM works like this:

• all modules and parts are listed once;
• rules decide which ones go in and how many: "one support per 60 cm of width", "with door option: two hinges per door";
• the final BOM only exists once the choices are known.

That moves the work around. You no longer make eighty new items a year. You keep one set of rules up to date. For a new colour, you add one value instead of dozens of items. If a supplier stops making a part, you change one rule.

The rules above are made-up examples. But the shape is always the same: if this, then that. Writing them down is often most of the work. CPQ data preparation explains how to approach that.

Some companies only design part of their product once the order comes in. For them, this is also how more of the product becomes something customers can simply choose. The article on ETO, CTO, MTO and ATO looks at that shift.

What a configurator adds

A configurator is a program where you put a product together by making choices. It's where the rules get carried out. The customer or sales rep chooses. The configurator checks that the combination works. Then it builds the BOM, the price and the quote.

Research suggests this helps. Keep in mind that most of the studies are old and small. A study of 238 manufacturing plants across three industries and eight countries, published in 2010, found this: plants that use a configurator do better on time. A 2013 study of four companies saw benefits such as less time to specify an order, on-time delivery and fewer part numbers. These are observations, not a guarantee.

A parametric model takes it a step further. That's a 3D model that adjusts itself when you change a size or option. The same rules that build the BOM then also build the 3D view. The customer sees exactly what they chose, built from the same modules the factory uses. You don't need a separate folder of pictures per variant that keeps falling behind. That's how we build 3D configurators. Parametric 3D product configurators explains how that works.

A configurator doesn't fix everything. If your product itself has no modules and no fixed connections, you only move the mess into another system. So work in this order. First, think of your product as modules. Then write down the rules. Only after that comes the configurator.

Closing thought

Eighty new part numbers a year don't mean something is wrong. They show that customers want choice and that you deliver it. The only question is how you keep track of those choices. As separate exceptions? Or as a set of building blocks and rules that every version comes from?

Our 3D & Development page shows how we turn rules like these into one model that adapts to every choice. Want to talk about your product range first? Get in touch.