Subtractive And Additive Machining: Differences Between The Two And Why They Matter

In the world of precision CNC machining, there are many different tools and processes used to create metal products. Two of these processes lie at the heart of metal machining. They are referred to as “subtractive processing” and “additive processing.” Here is an explanation of the differences between these two processes and why they matter.

Subtractive Processing

Subtractive processing is so named for the ways and tools that cut out, cut away or “subtract” from a larger piece of metal. For instance, if your company decides it needs several specific shapes cut from a single sheet of tempered steel, then the CNC machinist programs these shapes into the computer and sets up the laser cutter to cut the shapes out of the sheet of tempered steel. Because the laser is “subtracting” the unnecessary excess metal from the sheet to produce the flat steel shapes you requested, this would be an excellent example of subtractive processing.

Additive Processing

Additive processing, by contrast, is the process whereby metal objects and pieces are “added” to each other. This may mean that cylinders, tubes, sheets and other metal objects are joined together, usually through the process of welding, but they can also be bolted or attached in other ways. This process in machining is more commonly used to fabricate or replicate metal structures of the three-dimensional variety. Car manufacturing, specifically the engine construction and framework, are both examples of the additive processing variety of machining.

Why Their Differences Matter

Knowing that you can either add or detract from metal and metal objects to create the products you hope sell means that you have a wider variety of options on how to approach your metal products and projects. You could start two-dimensionally and build up until you get the results you expect, spending each moment overseeing the machining process that cuts metal away and builds it up layer by layer, or you could start three-dimensionally and continue adding various metal components.

More often than not, most metal product manufacturers use both subtractive and additive processes during some stage of production. In many cases, it is sometimes easier to use the subtractive process with precision CNC machining because you can always start with too much metal and then carefully cut it away with the precision lasers until you have the perfectly-formed items you requested. The precision aspect of this type of machining is within a fraction of a specified or chosen measurement, making the subtractive process a more appealing approach to your projects.