Posted December 3, 2020

What’s the Difference Between Additive Manufacturing and Subtractive Manufacturing?

Examples of additive manufacturing and subtractive manufacturing

In product development, high-quality parts are often needed quickly to avoid disruptions and keep the project on schedule. To satisfy the quality and schedule requirements, it’s necessary to gather all of the facts before fabrication decisions are made. Consider, for instance, the choice between manufacturing methods for precision parts.

If you need a part built quickly, the two common methods to choose from are additive and subtractive manufacturing. Both produce parts with numerous industrial applications, but their differences can determine the quality of the part. Understanding the differences between additive manufacturing and subtractive manufacturing will foster the most informed choice for your next project.

Two Approaches to Precision Parts Manufacturing

Additive manufacturing is often referred to as 3D printing. The difference between usage of the terms comes down to scale, where additive manufacturing is typically applied to industrial quantities. Additive manufacturing uses several different technologies to build parts in layers from the bottom up. These can include jet printing, deposited materials, and laser sintering. 

As “additive” implies, the required materials are added layer-by-layer to create the contours and shape of the part. As each layer of material is added, it bonds to the previous layer while still in a partially melted state. The data that drives additive manufacturing comes from a standard triangle language (STL) formatted file, which holds data for the entire part and is broken into individual 2D layers for printing.

Opposite of additive manufacturing is subtractive manufacturing. Subtractive manufacturing removes material layer-by-layer using lathes, mills, routers, and grinders. These tools are computer numerically controlled (CNC), and the data driving them is created by CAD/CAM systems used for mechanical design.

The Difference Between Additive Manufacturing and Subtractive Manufacturing for Component Production

Additive and subtractive manufacturing are used in the creation of high-quality precision parts, but it’s essential to comprehend the differences between them.

Materials

Additive manufacturing works with plastic and metal, just as subtractive manufacturing does, but the materials begin as a powder or resin and are slowly aggregated together into a final part. Subtractive manufacturing can work with plastics and metal in their stock forms, making them more accessible. Plus a greater range of materials can be machined rather than printed.

Waste

Since parts are built layer-by-layer, additive manufacturing uses only the necessary material, reducing waste. This situation is reversed in subtractive manufacturing as raw material is cut away from its source. Scrap from cnc-machining is easily recyclable.

Shapes

Additive manufacturing invites the potential for complex shapes. Unlike subtractive manufacturing, the additive method can create holes that curve and internal structures in fully closed parts.

Advanced CNC machine shops use machines on multiple axes to accommodate tight tolerances and complex geometries. Three and five-axis milling, for example regularly, produce holes with diameters of 0.020 inches. CNC turning technology can create grooves on inside and outside diameters as small as 0.020-inch wide. These are done with standard tolerances for metal down to +/- 0.005 inches, and even greater precision down to +/- 0.0005 inches depending on the geometry of the part.

Product Durability

Parts that are 3D printed may not have the same strength as a part that is machined from a solid core because the material is added in layers. This is a critical consideration for aerospace components or industrial parts, which may require machining to ensure they can withstand their rigorous applications.

Time and Expense

Additive manufacturing can be ideal when you need low volumes of a small component. However, it can become time-consuming—and expensive—when you need higher volumes of moderately sized parts. In these instances, subtractive methods, such as CNC machining, are often more efficient from a time and cost standpoint.

If you require a large production run of parts, subtractive manufacturing will generally be faster and more economical. On the other hand, additive manufacturing could be preferred if you need just a few prototype parts, or parts with complex designs.

Choosing the Right Manufacturing Method

Trying to decide between additive and subtractive manufacturing is like comparing apples and oranges—they both have their advantages and disadvantages. What’s important is to choose the method that aligns with your requirements. 

If you require a large production run of parts, subtractive manufacturing will generally be faster and more economical. On the other hand, additive manufacturing could be preferred if you need just a few prototype parts, or parts with complex designs. If the durability of the part is the prime consideration, CNC machining will be your best choice.

What is the best way to determine which manufacturing method is right for you? Work with an experienced and reliable machine shop that understands your needs and requirements. A high-quality shop will evaluate your design data and provide you the right manufacturing options for your project.

Plethora is an ISO 9001-certified machine shop specializing in the production of precision parts using the industry's most advanced CNC machining methods. We’re available to answer your questions about the difference between additive and subtractive manufacturing and look forward to partnering together with you for your next project. To get started, upload your design files to Quote My Part or call us at 415-726-2256.

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the-plethora-team

The Plethora Team

The Plethora team is your go-to CNC manufacturer for hardware done right the first time. We have the tools and experience needed to create high quality custom parts quickly and with precision, whether you need a prototype or production run.

Topics: Manufacturing, CNC machining, Prototyping

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