What is a digital twin?

A digital twin is a digital replica of something physical. GE defines it as “a software representation of a physical asset, system, or process,” while IBM calls it “a virtual model designed to accurately reflect a physical object.”

In additive manufacturing (AM), digital twins can be thought of as 3D models bundled with all significant information about the part: materials, manufacturing methods, tolerances, assembly instructions, certifications, and serial number. These twins can be stored on a computer or cloud database, ready to be printed at any time.

But the digital twin concept goes above and beyond additive manufacturing. Businesses can use virtual replicas of physical things for many reasons: analysis, simulation, failure prevention, quality control, and more. And these twins can represent anything from a metal screw to an entire electrical grid.

Autodesk offers a well-rounded explanation of the digital twin concept and its applications in the video below:

What is a digital inventory?

Digital inventories are databases of the digital twins in a company’s possession. They are both catalogs of parts and, in a sense, repositories of the parts themselves.

A digital inventory can replace or partially replace a physical inventory. For most companies, inventory is kept in a physical location: in draws or on shelves in warehouses, for example. When stock runs low, the company tops up the inventory. Some items — legacy spare parts, for example — never end up being used, but must be kept in storage anyway, just in case.

Digital inventories replace stores of physical parts with their digital twins. If a physical part is required, the company goes to its digital inventory, selects the digital twin, then follows the manufacturing instructions to produce it, making it into something physical.

Benefits of switching to a digital inventory

Switching to a digital inventory presents many advantages, most of which are in some way tied to reducing costs.

First and foremost, a digital inventory allows a company to reduce its storage or warehousing footprint. Certain physical parts can be replaced by their digital twin — which occupies no physical space — allowing companies to reallocate funds once used for storage.

Another advantage of warehouse digitalization is its ability to safeguard against supply and demand fluctuations. A digital twin is permanent; barring mass server failure, it cannot run out, so companies do not have to worry about stock levels or rely on third-party suppliers (which can potentially shutter or raise their prices). Conversely, companies with digital inventories do not get saddled with an overstock of parts that have been rendered undesirable or obsolete by market fluctuations.

Digital inventory leads to on-demand production — making parts only when needed — and this has its own benefits. By starting with a digital CAD file, companies can select certain colors, materials, or even design modifications based on a customer’s requirements — something that cannot be done with ready-made physical parts. Furthermore, if the digital twin contains all necessary manufacturing instructions, production can be carried out by nonspecialist staff, or even automated. This simplified on-demand production can be considered a form of lean or agile manufacturing.

Not all parts are good candidates for digitization, of course. Some are only made with traditional (non-digital) manufacturing techniques; others are ordered at such a frequency that it makes sense to keep a physical inventory of them. But some parts are perfectly suited to digital storage: niche parts, bulky parts, and spare parts for legacy, long-tail, or obsolete products, for example.

Limitations of switching to a digital inventory

Companies considering digitalizing (i.e. digitizing their processes) will have to weigh up the advantages against the limitations and potential downsides.

One disadvantage of using a fully digital inventory is an increase in lead times: fabricating a part on demand is slower than taking a prefabricated part off a shelf. And while digital part libraries reduce the need for regular inspection and upkeep, they are susceptible to issues like file corruption or accidental deletion.

Other risks include potential fluctuations in material prices (additive manufacturing powders, injection molding pellets, etc.) and potential manufacturing hardware or software obsolescence. Some of these problems can be mitigated by balancing digital and physical inventory.

How 3D scanning can help implement a digital inventory

For parts that were originally designed using CAD software, creating a digital inventory is simple: it can amount to little more than keeping those 3D models along with the significant information about them (materials, serial number, etc.).

For parts fabricated in other ways (or whose CAD files are inaccessible), companies can use 3D scanning to reverse engineer their physical parts. Some companies provide 3D scanning, reverse engineering, and inventory digitalization as a B2B service. Others provide software tools that identify parts suitable for digitalization.

A 3D scanner uses light and sensors to collect millions of data points from the surface of a physical object. The eventual output of the 3D scanning is a 3D model of the object, which forms the basis of a digital twin. 

Many structured light and laser triangulation 3D scanners can be used to reverse engineer parts in this way, though parts with very tight tolerances require higher resolution, metrology-grade 3D scanning equipment. The obtained scan data can also be used for part inspection, with specialized software that compares the data to the original file and generates automatic reports.

Once 3D scans have been obtained, implementing a functional digital inventory can be achieved in different ways.

In its simplest form, a digital inventory could simply be a folder or database of digital parts. However, more advanced solutions can be found via manufacturing execution system (MES), enterprise resource planning (ERP), and product lifecycle management (PLM) software packages, which integrate digital inventories with other internal systems such as order management and production planning.