Additive Method and Subtractive Method in Production

Before investing in production, we often think about the question of the choices of additive or subtractive manufacturing.
Additive method, often referred to as 3D printing, is particularly suitable for producing complex and intricate geometries, including organic shapes and internal structures that are difficult or impossible to achieve with traditional manufacturing methods, typically used for rapid prototyping, custom part production, and low-volume production.
Subtractive method is known for its precision and accuracy. It is often used to produce parts with critical tolerances and well-defined geometries. It is suitable for a variety of materials, including metals, plastics, ceramics and composites. It is often used to control repeatability and cost. In mass production with high efficiency requirements.
Let us know more about these two methods.

Methods Overview: Additive Method And Subtractive Method

A famous quote often attributed to the renowned Renaissance artist, poet, and sculptor Michelangelo captures the essence of creative craftsmanship. When inquired about how he crafted his iconic masterpiece, David, from a massive block of marble, he responded by saying that he simply “removed all the stone that did not resemble David.”

As both engineers and artists, our initial step in bringing an idea to life involves carefully selecting the most suitable tools and techniques for the job.

In its most fundamental form, manufacturing techniques can be categorized into two primary approaches: additive method and subtractive method. Additive method encompasses processes like fused deposition modeling and stereolithography, where components are built by layering successive materials to form the desired part from the ground up.

On the other hand, subtractive methods involve machining operations such as milling, CNC turning, laser cutting, wire EDM, and carving, much like how Michelangelo meticulously carved David from a raw block of marble.

Explore further for a comprehensive understanding of the key factors to consider when determining the appropriate manufacturing approach for your product development endeavors.

Four Considerations for Method Selection

When it comes to deciding which manufacturing method to employ, there are four overarching considerations that will assist you in making an informed decision about additive method and subtractive method. In assessing these considerations you’ll have a better understanding of your project requirements, which will point you toward the best tools for the job.

Material Selection

For Most Plastics: Opt for Additive Method
Additive manufacturing is most suitable for a wide range of plastic materials, including ABS (Acrylonitirle butadiene styrene), PLA (Polylactic Acid), PVA (Polyvinyl Alcohol Plastic), nylon, and resins. Although ceramics and metals are increasingly utilized in 3D printing, they are presently limited to specialized, higher-cost machines and not yet ideal for most production needs. For low-volume casting methods, 3D printed parts can be used to create silicone molds for casting in various materials.

For More Material Variety: Consider Subtractive Method
Subtractive methods can accommodate a diverse array of materials, such as engineering metals (e.g., aluminum and steel), wood, foams (e.g., polystyrene or structural foam), and ceramics. This versatility provides greater flexibility, enabling cost-effective solutions for larger parts, unlike producing very large 3D printed plastic parts.

Part Quantity

For Low Volume Production: Opt for Additive Method
Additive method is well-suited for prototype or low-volume production runs, typically ranging from one to ten parts, owing to speed and relative unit cost. They offer the ability to produce a complete set of different parts in a single run, a feat difficult to achieve using subtractive methods such as milling or lathing.

For High Volume Production: Consider Subtractive Method
When you need to manufacture a large quantity of parts, subtractive methods, such as machining, remain the preferred approach. Modern CNC machining offers high part-to-part repeatability and can efficiently produce large volumes of identical parts in a short timeframe. Furthermore, steel dies for injection-molded plastic components are created using subtractive manufacturing methods.

Part Geometry

For Organic Surfaces and Complex Features: Opt for Additive Method
Additive method is the most effective way to produce parts with intricate geometry. 3D printers can create features that are impossible to machine, including ‘captured’ components. However, note that the precision and level of intricacy in 3D-printed parts are influenced by factors such as minimum layer thickness and material type, necessitating higher-end materials and machines for achieving desired feature precision.

For Dimensional Accuracy and Repeatability: Consider Subtractive Method
Subtractive methods are generally superior when precision for common functional features (e.g., flat faces, drilled and tapped holes, counterbores, and mating components) is crucial. This is because subtractive methods can produce parts using very dense, hard materials like steel and aluminum, which can be machined to a high degree of precision.

Project Schedule and Part Revisions

For Faster Lead Times and Iterative Prototyping: Opt for Additive Method

3D printing offers faster lead times compared to machined parts, making it ideal for iterative prototyping and quick testing of revised designs. The use of additive technology can significantly reduce production cycles, enabling multiple iterations of part design prototypes to assess fit and function before moving to manufacturing with machining methods. In contrast, revisions to machined parts may involve adjustments to programmed tool paths, setup, and machining operations, all of which consume considerable time. Planning for several 3D printed iterations is a best practice for testing and refining designs before committing to machining-based production.

Key Takeaways: Additive Method and Subtractive Method

Selecting the most suitable manufacturing method hinges on understanding your design requirements. As a starting point, consider these three essential questions:

What are your product’s features?
If your product boasts small, organic, and intricate features, additive method is ideal.
For products with large or sharp features, drilled and tapped holes, or other fastening elements, subtractive method is more appropriate.

What material do you intend to work with?
Opt for additive method when working with thermoplastics and resins.
Choose subtractive methods when dealing with materials such as metals, wood, or foam.

How many units are you planning to produce?
Additive method is well-suited for low-volume production or iterative prototyping.
Subtractive method is the preferred choice for large-volume production runs.

By thoroughly evaluating your design criteria, the most suitable methods and tools for each stage of your production cycle will become evident.

Additive Method and Subtractive Method at Sungplastic

As a plastic and metal parts or products manufacturer, we are very familiar with these two manufacturing methods (additive and subtractive), and have mastered their process, successful production cases, the ability to provide advanced equipment support, the assistance of professional designer and engineers, strict control of production, and competitive prices and services.

If you need the helps of additive manufacturing and subtractive manufacturing, welcome to consult with us.

Related Resources:

Guide of CNC Manufacturing Custom Parts

CNC Prototyping from Custom Prototypes to Production

Plastic Injection Molding Service

3D Prototyping: Guides To 3D Rapid Prototypes Manufacturing