Subtractive Manufacturing or Additive Manufacturing

Globally, additive and subtractive manufacturing have become increasingly popular in recent years. Many industries now profit from the creative production of various parts due to technological advancements.

Because of their overlapping application modes, additive and subtractive manufacturing implementation methods are dependent on each other even though they differ from one another. However, other elements like production volume and product development stage affect the manufacturing process used to produce a prototype or part.

The comparison between subtractive manufacturing and additive manufacturing is the main focus of this educational article. We also point out the key distinctions between the two manufacturing processes, as well as their benefits and drawbacks, and primary uses.

Subtractive Manufacturing

Subtractive manufacturing involves the removal of material from a solid block of metal, plastic, or wood to create a new product. For example, a milling machine can hollow out metal or plastic objects through cutting.

This manufacturing technology enables the design, prototyping, and production of end-use materials, making it suitable for both small and large volume productions. It offers the advantage of achieving specific mechanical properties or finishes. Subtractive manufacturing utilizes materials such as aluminum, brass, ABS, Delrin, Nylon, PEEK, PVC, plexiglass, PCA, Polypropylene, and wood.

One of the benefits of subtractive manufacturing is the ease of matching the design with the desired material properties, including strength, flexibility, chemical resistance, and other dielectric properties.

Pros and Cons of Subtractive Manufacturing

Pros:

• Works with various materials like metal, plastic, wood, and composites.
• Can create different shapes, including holes, cylinders, screw threads, and flat surfaces.
• Provides a smooth surface finish.
• Offers high accuracy with close tolerances.

Cons:

• Generates material waste and chips, although some can be recycled.
• Takes longer production time compared to additive manufacturing.

Types of Subtractive Manufacturing Processes

Subtractive manufacturing encompasses various processes, including cutting, machining, and abrading. Here’s an overview of each:

Laser Cutting

This process utilizes a laser beam to precisely cut different materials into desired shapes. It finds applications in industrial and artistic sectors. Laser cutting involves the use of Computer Numerical Control (CNC) and optics to direct the laser beam. A motion control system ensures accurate cutting following the desired pattern. Vaporization or high-pressure gas assists in achieving a high-quality surface finish.

CNC Machining

CNC machining involves using pre-programmed computer software to guide industrial tools and machinery. It enables three-dimensional cutting tasks with a single set of commands. Prior to operation, the necessary cuts are programmed into the software, which then instructs the equipment and machinery to carry out the defined dimensional operations. While errors can occur, especially when the CNC machine cuts in multiple directions simultaneously, the code generator in the numerical control system assumes flawless operation. The part program, a set of inputs, determines the tool’s positioning within the numerical control system.

Abrading

Abrading is a subtractive manufacturing process that involves the use of abrasives to grind or brush away material. Abrasives are rough substances that can grind, sand, or polish materials. They are applied through constant rubbing to remove material or achieve a smoother surface. Abrasives can be attached to a hard surface or suspended in a liquid for more efficient use. It is important for abrasives to be harder than the material being removed for optimal effectiveness.

EDM (Electrical Discharge Machining)

EDM, also known as spark machining, spark eroding, die sinking, wire burning, or wire erosion, is a subtractive manufacturing technology that utilizes electrical discharges to shape materials. The process involves a series of rapid current discharges occurring between two electrodes (tool and workpiece electrodes) separated by a dielectric liquid and subjected to an electric voltage. Material removal from the workpiece is achieved through this EDM process, and physical contact between the tool and workpiece is not necessary.

Subtractive manufacturing processes offer precise control and versatility in shaping materials, allowing for the production of various complex parts and components.

Additive Manufacturing

Additive manufacturing, also known as 3D printing, is an industrial process that utilizes computer control to create three-dimensional objects by layering materials onto a base material.

The fundamental principle of additive manufacturing is the addition of materials to build a new object. Various materials can be used in the printing process, including metal alloys, thermoset polymers, composites, and thermoplastics.

Initially, additive manufacturing found its primary applications in the aerospace and medical industries. However, its reach has expanded to encompass a wide range of industries. Today, sectors such as automotive, oil and gas, and heavy equipment are just a few examples of the ever-growing utilization of additive manufacturing technology.

Pros and Cons of Additive Manufacturing

Pros:

• Efficiency and waste reduction.
• Faster design-to-production time.
• Easy creation of complex designs.

Cons:

• Limited material options.
• Higher cost when using metals.
• Not ideal for large-scale production.

Types of Additive Manufacturing Processes

Additive manufacturing processes are categorized into seven main types:

Binder Jetting

This process involves selectively depositing a binder onto a powder bed to form solid layers. It is suitable for granular materials such as metals, sand, and ceramics.

Directed Energy Deposition (DED)

A complex process where a focused energy source, like a laser or beam, melts a powder or metal wire that is precisely deposited onto the build platform to form each layer.

Material Extrusion

Similar to a glue gun, this method uses a nozzle to extrude material, usually in coil form, which is melted and layered on the build platform to solidify and create the object. It is relatively affordable but has some limitations.

Powder Bed Fusion (PBF)

This category encompasses various AM processes such as Direct Metal Laser Sintering (DMLS), Selective Laser Sintering (SLS), Selective Heat Sintering (SHS), Electron Beam Melting (EBM), and Direct Metal Laser Melting (DMLM). PBF employs lasers, beams, or print heads to melt and fuse fine layers of material, with excess powder removed after each layer.

Sheet Lamination

This includes methods like Laminated Object Manufacturing (LOM) and Ultrasonic Additive Manufacturing (UAM). UAM joins thin metal sheets through ultrasonic welding, while LOM uses adhesive-coated paper sheets for visual and aesthetic modeling objects.

VAT Photopolymerization

In this process, an object is produced in a vat of liquid resin photopolymer. The resin is cured layer by layer using ultraviolet lighting, directed by mirrors.

Material Jetting

Similar to binder jetting, but instead of adhesive, this method uses wax. It deposits layers of wax onto the build platform, offering cost-effectiveness and high-quality surface finishes with improved accuracy.

These different additive manufacturing processes provide versatility in terms of materials, complexity, and cost, catering to various applications and industry needs.

Differences: Additive Manufacturing vs Subtractive Manufacturing

Additive manufacturing processes involve building products by adding materials layer by layer, while subtractive manufacturing removes parts of a solid material to create the product components.

Here are some notable differences between additive and subtractive manufacturing:

Material Options

Additive Manufacturing: Narrow range of materials, mostly plastic derivatives, including ceramics, thermoplastics, metals, and resins.
Subtractive Manufacturing: Wide range of materials, such as glass, metal, plastic, wood, and composites.

Achievable Complexity

Additive Manufacturing: Ideal for complex designs.
Subtractive Manufacturing: Best suited for less complex designs, but can handle large batches of complex designs.

Accuracy

Additive Manufacturing: Requires additional machining for high accuracy.
Subtractive Manufacturing: Generally more accurate, especially with CNC machining.

Properties Of Finished Parts

Additive Manufacturing: Products may have surface pores, requiring additional cleaning and finishing.
Subtractive Manufacturing: Produces stronger parts with better finishing.

Surface Finish Choices

Additive Manufacturing: Can result in poor surface finish, requiring additional surface treatments.
Subtractive Manufacturing: Provides smoother surface finishes and better tolerance.

Speed

Additive Manufacturing: Faster for prototyping and small volume production, but slower for mass production of plastic parts.
Subtractive Manufacturing: Generally faster for mass production.

These differences in material options, complexity, accuracy, properties of finished parts, surface finish choices, and speed highlight the contrasting characteristics of additive and subtractive manufacturing processes, allowing for informed decision-making based on specific needs and requirements.

Subtractive vs Additive Manufacturing Cost

Comparing the Cost of Subtractive and Additive Manufacturing:

Machinery and Tooling Costs

Additive Manufacturing: Acquiring and installing precision additive manufacturing equipment can be expensive, making machinery investment the primary contributor to additive manufacturing costs.
Subtractive Manufacturing: Tooling expenses are essential for each subtractive manufacturing process, requiring design and implementation.

Labor Costs

Additive Manufacturing: Due to high automation, labor costs account for a small proportion of total costs. Simplifying parts reduces labor requirements and associated costs.
Subtractive Manufacturing: Labor costs are also minimized due to automation, and simplification of parts reduces labor needs.

Material Costs

Additive Manufacturing: Materials used in additive manufacturing tend to be more expensive than those used in subtractive manufacturing. The cost difference can be significant, with materials for additive manufacturing being up to eight times costlier on a per-weight basis.
Subtractive Manufacturing: Material costs for subtractive manufacturing are generally lower.

Post Processing Costs

Both Additive and Subtractive Manufacturing: Post-processing is often required to achieve the final product state, including processes like washing, polishing, or removing surplus material. Post-processing costs are similar for both manufacturing methods and are inevitable.

It’s important to consider these cost factors when deciding between subtractive and additive manufacturing processes. Each method has its own cost considerations based on machinery, tooling, labor, materials, and post-processing requirements.

Applications of Additive vs Subtractive Manufacturing

Additive Manufacturing Applications:

• Jewelry production.
• Aerospace industry.
• Energy system improvement.
• Model fabrication for industries.
• Robotic and electromechanical systems.
• Solid freeform features.
• Metamaterials, electromagnetics, and 3D electronics.
• Dental and medical elements.

Subtractive Manufacturing Applications:

• Contoured profile and textured surfaces fabrication.
• Cutting features for household, automobile, electronics, aerospace, dental, and medical industries.

Hybrid Process from Product Design to Prototyping

The benefits of additive manufacturing over subtractive manufacturing are often maximized by hybrid systems, and vice versa. Additionally, they blend the benefits of additive and subtractive manufacturing. Both systems are managed by specialized machinery, which is excellent for fixing damaged parts. Complex parts can be easily produced with hybrid manufacturing because they can be layered and then finished with milling tools.

We carry out these production procedures from concept to prototype. In order to satisfy our clients’ demands and uphold the necessary standards, we also manufacture the highest-quality parts.

In addition, we promise the best automated DfM analysis and offer immediate quotes. Furthermore, we accomplish these procedures by combining our hardworking staff with our robust manufacturing capabilities to guarantee the prompt delivery of the highest-quality parts.

FAQs

Which is better: Additive or Subtractive Manufacturing?
The trend toward reduced waste makes additive manufacturing the superior choice. In addition, by layering components together to create a final product, additive manufacturing mimics natural processes. Compared to subtractive manufacturing, it produces less waste. It also generates complex designs more effectively and faster.

Is Injection Molding belonging to Additive or Subtractive Manufacturing?
Neither of them. Injection molding are not the same as subtractive and additive manufacturing . Rather, it is a manufacturing technique that facilitates large-scale production. Additionally, molten material is injected into a mold during this production process. The intended final product’s shape would be reflected in this mold.