Will Additive Manufacturing Replace Subtractive Manufacturing?

Sarah is a sales & marketing content writer, with ten years of experience within the engineering & manufacturing industry.  Working both at Qimtek and on a freelance basis, she can usually be found hammering away at a keyboard or with her head in a pile of engineering drawings. 

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As one of the newer kids on the engineering block, additive manufacturing has seen a surge in popularity in recent years. Many manufacturers have discovered that additive manufacturing and 3D printing are versatile techniques that offer a plethora of benefits. As a result, some manufacturers have turned to additive manufacturing as a replacement for more traditional engineering processes such as machining and casting. But is additive manufacturing likely to replace subtractive manufacturing altogether?

Additive Manufacturing vs. Subtractive Manufacturing:

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The difference between the two processes lies in the name. Additive manufacturing is so called because it produces components by adding layers of filament on top of each other until the desired shape of the part is reached. Additive manufacturing is commonly referred to as 3D printing for this very reason - the component is 'printed' into reality from a CAD file using a 3D printer. 

The ground that additive manufacturing has gained in such a short span of time is astonishing.

Subtractive manufacturing, however, starts with a block, bar or billet of material and removes any excess until the form of the part is achieved. Machining processes such as milling, turning, gear cutting, grinding and EDM are all examples of subtractive manufacturing processes which are commonly used - in fact, it could be argued that subtractive manufacturing is still the most popular production method throughout the industry as a whole.

However, given that additive manufacturing as a concept was only developed in the 1980s, with more widespread commercial use commencing in the 2000s, the ground that it has gained in such a short span of time is astonishing. This has led many to wonder whether additive manufacturing could ultimately replace subtractive manufacturing in future.

Pros and Cons:

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The most obvious advantage that additive manufacturing has over subtractive manufacturing is a reduction in material wastage. Although 3D printed parts may sometimes require secondary operations to ensure that they are fit for purpose, they generally use as much material as is required. The same cannot be said for subtractive manufacturing, which often results in much more waste. This benefit of additive manufacturing extends not only as far as a cost-saving for manufacturers, but also as an answer to the increasingly pressing question of how we can make manufacturing more environmentally friendly as a whole.

Additive manufacturing allows for a much broader scope when it comes to component complexity.

Additive manufacturing also allows for a much broader scope when it comes to component complexity, achieving intricate shapes with far more ease than its subtractive counterparts. This is particularly useful when it comes to the manufacture of hollow parts which would be difficult to produce via other means. Another benefit of additive manufacturing is that it doesn't require tooling - although this is more comparable to the likes of casting and moulding than subtractive manufacturing processes, the lack of tooling requirements - and therefore cost savings - have been more than enough for a lot of manufacturing companies to look at AM processes more closely.

However, additive manufacturing still has a number of limitations. Whilst it is currently well-suited to prototyping and small batch runs, the 3D printing process can be very slow, making it difficult for companies to utilise additive manufacturing for high volume production. Although material wastage is vastly reduced, it is also very limiting when it comes to the materials that can be used, due to the fact that the material is extruded through a nozzle within the 3D printer. 

On the other hand, subtractive manufacturing offers users almost an unlimited choice of materials. Everything from plastic, rubber and metals such as aluminium, stainless steel and mild steel, through to exotic materials such as inconel and titanium can be catered for. Generally speaking, subtractive manufacturing also produces stronger, more durable parts than additive manufacturing as it uses solid material; however, technology in the AM field is ever-evolving as it is adopted by more and more safety-critical industries such as aerospace and medical.

Subtractive manufacturing is also much more versatile when it comes to batch sizes.

Subtractive manufacturing is also much more versatile when it comes to batch sizes, with most machines able to handle both prototyping and full production with ease, adhering to tight tolerances and offering a very high degree of precision and accuracy. The trade-off is that subtractive manufacturing processes often have a much longer set-up time when compared to additive manufacturing, which requires little more than a 3D design file to get started. 

The main disadvantage of subtractive manufacturing is its limitations when it comes to producing complex components. Although multi-axis machines can be used to create a wider variety of shapes, additive manufacturing is by far the better choice for achieving great results on highly complex structures and parts. This is one of the main reasons for the 'buzz' surrounding AM technologies - it has made what was once thought to be impossible a reality and afforded product designers much more ambition in their work.

Will Additive Manufacturing Replace Subtractive Manufacturing?

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As it currently stands, it is unlikely that additive manufacturing will replace subtractive manufacturing any time in the near future. This is because both sets of processes have a very contrasting set of advantages and disadvantages, meaning that each can play to the strengths of the other's weaknesses. Until additive manufacturing is able to speed up production times to accommodate larger batches and offer a wider range of materials, it is probable that additive and subtractive manufacturing will continue to peacefully coexist.

With that being said, the evolution of additive manufacturing has - and continues to be - extremely fast. Innovation within the AM sphere has moved at unprecedented speed, meaning that it is now possible to produce a wider range of parts than ever using additive manufacturing and 3D printing. Moving forward, this is definitely an area for the manufacturing industry to watch with interest; in the meantime, subtractive manufacturing will remain one of the staple groups of processes that manufacturers rely upon.