The manufacturing industry relies on two approaches to create the parts from raw materials; additive and subtractive. These two techniques have their own importance according to the requirement and workpiece material. The main difference between these two is associated with wheatear the process involves the removal of material or not to create the desired shape from raw material.

Subtractive manufacturing continuously removes the material from the outer surface until it is converted into the required shape. In contrast, the additive approach creates the desired shape by adding layers of materials.

This article will cover comprehensive detail about subtractive and additive manufacturing techniques, their advantages, disadvantages, comparison, and many more.

 

What is Subtractive Manufacturing?

It is the manufacturing technique where the functional parts for different applications are made with material removal from the workpiece. The material removal process involves machining tools and equipment, such as cutters, milling tools, drill bits, lathe machines, CNC machines, EDM machines, and many more.

Subtractive manufacturing process

The subtractive manufacturing approach has been around since the initial phase of human civilization. At the early stage of evolution, humans used this approach to create hunting tools, arts, and other items.

In modern manufacturing, subtractive manufacturing plays a significant role. Several appliances, mechanical systems, tools, arts, medical implants, aerospace parts, rocket parts, defense systems, and parts for other industries use a subtractive manufacturing process.

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Types of subtractive manufacturing

There are several methods for removing material to generate the parts. These techniques have their own benefits, drawbacks, material choices, and applications. Let’s quickly review each of them individually.

1. CNC Machining

CNC machine

CNC (Computer Numerical Control) machining is the widely used subtractive manufacturing approach to create 3D objects. Since its invention in 1950, it has been renowned as a prominent manufacturing Technology (Oyoun, 2020). It has a significant role in revolutionizing the manufacturing industry. If we talk about automation, CNC is the leading technology that can create precise parts using 3D models and digital instructions.

Various CNC machining operations follow the subtractive approach to create precise parts from almost every material.

• CNC Milling

Traditional CNC milling involves a rotating tool and stationary workpiece, while modern mills can rotate both workpiece and machining tools. It removes the material from a workpiece by feeding into a rotating tool or vice-versa. The multi-axis movement of the tool eliminates the material and creates the exact shape according to the uploaded 3D model by dictating the movement of the tools with computer control.

• CNC Routing

CNC Routing is another subtractive manufacturing technique that removes the material from the workpiece to manipulate it into the desired shape. The CNC router machine handles the routing operation, which is similar to milling but results in less material waste and can produce designs with more precision and complexity.

• CNC Turning

In CNC turning, a tool is fed into a rotating cylindrical workpiece. Material from the workpiece surface is removed during the turning process by fed into the tool to produce the desired geometry. The CNC turning also involves control of the removal process with computer software.

2. Electric discharge method

This technique uses an electric arc to cut away material from the workpiece and shape it into the desired form. The electric discharge method can work with hard metals. CNC EDM machines are popular in the manufacturing industry, which can precisely cut and engrave the material with computer control.

3. Laser cutting

Laser cutting is the process of cutting the workpiece with a high intense Laser-beam. The Laser beam strikes the cutting position and splits the workpiece with the help of Intense Heat. However, it is not only applicable to split the workpiece. Laser beams can engrave, drill, mark, and weld the materials.

4. Water-jet cutting

The water-jet cutting technique involves the line-cutting of raw material using a high-pressure water jet. The foundation is the idea of water erosion. Material removal happens when a high-velocity water jet contacts the surface.

Advantages of Subtractive Manufacturing

Precision is the main advantage of the subtractive manufacturing approach; it allows the creation of the parts by material removal with tolerances as low as 0.005mm.

The following are the other key advantages;

• It is compatible with almost every material, metal, alloy, wood, plastic, composite, ceramic, etc.
• The subtractive approach leaves a smooth surface finish.
• It is a quick process and suitable for large-volume production.
• Subtractive manufacturing can create almost every feature, hole, engrave, thread, and more.
• It is cost-effective for mass production.
• It can create complex shapes with a high degree of dimensional accuracy.

 

Disadvantages of Subtractive Manufacturing

Material waste is the fundamental drawback of subtractive manufacturing since it uses material removal to generate the desired shape.

The following are the other key disadvantages;

• It is impossible to control material density, which entirely depends on the composition of raw material (George Belgiu, 2021).

• High installation cost because it requires different equipment setups for each operation.
• It can be messy since there can be many steps to create one shape.

 

What is Additive Manufacturing?

The additive manufacturing approach involves creating a 3D object by adding or joining the material, where the material can be in powder, layer, wire, sheet, or liquid.

3D- Printing process

It also has been an efficient manufacturing process that has been around for centuries. At the dawn of civilization, additive manufacturing was employed to create various mud products.

It has developed into an automated procedure known as 3D printing in modern manufacturing. It is compatible with an extensive range of material options in the current scenario, such as metal, alloys, thermoplastics, composites, and many more. Different industries like automotive, oil, gas, and energy utilize this technique to create the parts and equipment.

 

Types of additive manufacturing

Additive manufacturing techniques

Like the subtractive manufacturing approach, it also has various distinct techniques to create the 3D object by adding materials of different forms.

1. Directed Energy Deposition (DED)

It uses metal wire or powder as raw material and binds to create functional parts and products. The powder or wire is melted by a different form of energy (laser is typical) and subjected to a building platform in a molten phase. Then, solidification creates the desired shape.

2. Binder Jetting

The Binder Jetting technique utilizes the raw material (metals, sand, and ceramics) in granular form. The granular structure of raw material is subjected to a powder bed, where it forms the required shape by adhesion of repetitive deposition.

3. Extrusion method

This process utilizes the molten form of material to create the parts. It uses the printer, which involves the adhesion of multiple layers. Generally, the raw material in wire form is subjected to a nozzle, where the nozzle tip melts the material and passes to the building platform.

4. Other methods

There are several other additive manufacturing methods: sheet lamination, powder bed fusion, VAT photo-polymerization, material jetting, and more.

 

Advantages of Additive Manufacturing

Since additive manufacturing involves adding material instead of removing it to create the geometry, material wastage is the fundamental advantage. It does not waste the raw material in the process.

The following are the other key advantages;

• It is a quick process from designing to the creation of physical parts.
• The creation of intricate shape is possible with an additive manufacturing approach and offer design flexibility.
• It is cost-effective when it comes to rapid prototype development
• Repeatability can be achieved more effectively with the additive manufacturing method.
• It keeps the dimensional consistency in large-volume production.
• Material density can be controlled easily.
• It is more environmentally friendly because of negligible material wastage.

 

The disadvantage of Additive Manufacturing

• The additive manufacturing results in a poor surface finish.
• It is not suitable for mass production.
• There are fewer material options for additive manufacturing.’
• It can cause the degradation of mechanical & physical properties.

 

Comparison based on Different Aspects

Choosing the manufacturing approach for your project might be tricky because both methods have different benefits and drawbacks. So, let’s compare them based on various aspects.

Criteria for comparison	Subtractive Approach	Additive approach
Material option	Almost every material, metal, alloy, composite, plastic, wood, composites, ceramics, and more.	Fewer material options, metal, alloys, thermoplastics, and a few composites.
Accuracy	More precise, tolerances are as low as 0.025mm.	Less precise, tolerances are as low as 0.1 mm.
Material wastage	Although wastage can be recycled in the majority of cases, more material wastage	Negligible material wastage
Lead time	Quick process	Less lead time than subtractive for prototype development
Mass-production	Cost-effective for mass production	Less cost-effective than the subtractive approach
Automation	More automation	Less automation
Part-size	Suitable for both small and large size	Suitable
Design flexibility	Less design flexibility	More design flexibility
Environmental Effects	Less environmental friendly	More environmentally friendly. However, it might involve the emission of toxic gases depending on the material type.
Installation cost	High	Low
Complexity	More complex	Less complex
Surface finish	More quality	Less quality and requires post-processing in the majority of cases.

 

Conclusion

Subtractive and additive manufacturing processes are two prominent methods in the manufacturing industry. These two approaches have their own benefits and drawbacks under different circumstances. However, subtractive is more reliable since it is more evolved, precise, cost-effective, and applicable to various industries.

ProleanTech offers dedicated and precise subtractive manufacturing services, including CNC machining, laser cutting, water-jet cutting, wire cut, and electrical discharge machining. We have cutting-edge technologies and expert engineers to meet your expectations. So, send us your design and get the parts within a few days at your doors.

 

FAQ’s

Which method is more popular subtractive or additive?

Subtractive manufacturing is more popular than additive. Since additive technology is still developing, subtractive is the more evolved technique. It is better to use a subtractive approach. However, the prototype development of some thermoplastics can be more effective with additives.

What are some standard subtractive manufacturing techniques?

CNC machining, Laser cutting, water-jet cutting, electrical discharge machining, and wire cut are some standard subtractive manufacturing techniques.

Which is more precise and cost-effective?

The subtractive method is more precise and cost-effective. It can maintain a tolerance as low as 0.025mm.

 

Bibliography

1. George Belgiu, C. T. (2021). Selection of Subtractive Manufacturing Technology Versus Additive Manufacturing Technology for Rapid Prototyping of a Polymeric Product. ResearchGate.
2. Oyoun, L. (2020). Computer Numerical Control. ResearchGate.