Subtractive vs Additive Manufacturing: Examining the Differences

Introduction

With continued technological advancements, different manufacturing processes exist for creating parts and components. However, due to their vast capabilities, subtractive vs additive manufacturing processes have become the mainstay.

While both operations are distinct, they are inventive and have significantly impacted manufacturing. Even though there are other manufacturing techniques, most components are created with either process. 

This article explores the distinction between subtractive vs additive manufacturing services. Read ahead! 

What is Subtractive Manufacturing?

Subtractive manufacturing means what the name indicates. It involves removing pieces of a workpiece or material to create something new. It’s a size reduction process that often starts with a large chunk, sheet, or solid block, and then, upon application of a series of cutting techniques, you arrive at your intended shape, size, geometry, and features of the product.

The technology starts from the designing and prototyping phase before proceeding to the actual manufacturing or fabrication process. It is suitable for creating complex designs and structures with high precision and dimensional accuracy.

Subtractive manufacturing technology is highly versatile, supporting different material options, including metals, alloys, plastics, resins, composites, glass, etc. Also, it is a mainstay in various manufacturing industries because of its vast capabilities.

What is Additive Manufacturing?

As the name suggests, additive manufacturing involves creating parts by joining pieces of a material. It is commonly called 3D printing, a computer-controlled manufacturing technique that forms parts by depositing material to form a part’s intended shape and structure.

However, it includes an extensive list of other manufacturing techniques used to create components. Like the subtractive technique, it is also compatible with many material options – plastic polymers, metal alloys, and composites.

Moreover, it also offers applications in various industries, especially aerospace and medical industries, where precision is critical in fabrication.

Common Types of Subtractive Manufacturing Techniques 

We hinted earlier that subtractive manufacturing encompasses various cutting techniques. Let’s examine some of them.

CNC Machining

CNC machining involves using computer programs and codes to guide a series of cutting tools to maneuver through a workpiece. The software acts as the brain of the operation. After configuration, the device sets out to achieve the aim of the fabrication, creating your desired shape and structure.

The method is widely accepted in various industries because of its high regard for precision and maintaining dimensional accuracy, even when creating complex parts. However, there are different CNC machining operations – milling, turning, and drilling, to mention a few. Therefore, you must understand the suitability and purpose of each technique, including the machinery, to ensure a successful fabrication.

Laser Cutting

Laser cutting involves using high-focused beams (laser) to cut and shape a material. The technique typically adopts CNC operations to control, focus, and direct the path of the laser to ensure and improve its accuracy as the laser vaporizes the workpiece following the designed toolpath. The process is not as versatile as general CNC machining. However, it’s compatible with plastic polymers and metals, especially sheets and plates. That said, laser cutting is suitable for general industrial manufacturing and decorative purposes, like engraving, where it serves as a surface finish.

Water Jet Cutting

As the name implies, water jet cutting involves using highly pressurized water to cut through materials. The water is usually mixed with abrasive particles – mainly fine garnet – to enhance its cutting efficiency. The process benefits cutting materials and workpieces sensitive to the high temperatures generated in other subtractive manufacturing processes.

Grinding

Grinding is another subtractive manufacturing method that uses abrasive materials to enhance its cutting ability. It is an abrasive machining process that converts a grinding wheel into a cutting tool. The process is well suited for achieving smooth surfaces and dimensional accuracy of a part. This feature sometimes makes grinding fit as a surface finish for metal parts.

EDM – Electric Discharge Machining

As the name suggests, electrical discharge machining converts electrical discharge into a cutting tool. This unconventional machining method creates sparks from electrical current channeled into the cutting tool to machine the part. EDM is typically suited for cutting hardened metal pieces that may prove challenging for conventional methods.

Benefits and Shortcomings of Subtractive Manufacturing Methods

We already extensively discussed subtractive manufacturing, including some of the methods adopted for this technique. Below, we will examine some of its benefits and shortcomings.

Benefits

• Suitable for an extensive range of materials, including metals, alloys, plastics, resins, wood, composites, and ceramics.
• Suitable for creating parts of various shapes, structures, and geometries
• It retains the material’s structural integrity and overall mechanical properties, making this technique the go-to choice for fabricating structural and construction components.
• Produces parts with high precision and accuracy, up to 0.025 mm tolerance level
• Creates parts with good surface finishing; in fact, some do not require extra finishing operations.

Shortcomings

• It is almost impossible to avoid waste, though many materials may be reused.
• Tool wear is almost unavoidable; hence, there is a need for routine tool maintenance.
• Subtractive manufacturing takes longer production time than additive manufacturing.

Common Types of Additive Manufacturing Techniques 

Additive Manufacturing (AM) involves using digital models to create solid components in layers. Below, we discuss some techniques for AM.

3D Printing 

3D printing is the ultimate additive manufacturing process. It involves building parts and structures in layers from a digital model till the entire three-dimensional component is achieved. The method is suitable for creating almost any structure that can be envisioned, making it the go-to technique for rapid prototyping and manufacturing intricate details and designs. Sometimes, manufacturers just use it to create a prototype to check the efficiency of a digital 3D model and if the intended design will suit the part’s functionality.

Binder Jetting

Binder jetting is another additive manufacturing process that involves creating a part in layers till the entire fabrication is attained. The technique selectively deposits a liquid binding agent onto a powdered material to form solid layers. The method is suitable for creating complex structures and is compatible with different material options, including metals, ceramics, and composites.

However, the materials must be granular, as the roller spreads evenly throughout the build form during fabrication before adding the adhesives. The process is then continued till you have the intended 3D structure. You can then proceed to secondary and finishing operations like curing and sintering.

Metal Extrusion

This additive manufacturing process involves feeding the material, in this case, a metal wire or powder, and melting it through the nozzle of a glue gun. As the metal pieces melt, they are placed on the build platform in layers to solidify. This process is repeated till the entire object is created. It is important to note that this manufacturing technique is not restricted to metals. It is compatible with various engineering-grade thermoplastics. However, it is the most expensive additive manufacturing method, though it creates parts with good mechanical properties.

Sheet Lamination

Like all additive manufacturing processes, sheet lamination builds parts in layers. The technique occurs in two forms: Ultrasonic Additive Manufacturing (UAM)  and Laminated Object Manufacturing (LOM). Both processes involve binding material sheets together to create the desired part. However, UAM uses ultrasonic welding to bind materials, while LOM uses an adhesive coating paper sheet as its base material. The resulting fabrication is usually visually appealing; consequently, the method is used for aesthetic modeling and decorative purposes. It is important to note that the process is not restricted to only paper and non-metals; sheet lamination can also create metal components.

Benefits and Shortcomings of Additive Manufacturing Methods

We already discussed some of the standard techniques used to achieve additive manufacturing. Below, we will list some of the advantages and disadvantages of this technique.

Benefits

• Creates almost zero waste
• AM is a quick and efficient production process, making it a good choice for rapid prototyping.
• It is ideal for creating complex structures, regardless of design complexities and intricate detailing, including tight tolerance specifications.
• Suitable for customization and creating rare parts and structures.

Shortcomings

• Expensive, especially for metal part fabrication
• Compared to subtractive manufacturing, it’s material compatibility is limited.
• Best suited for low-volume production

Subtractive vs Additive Manufacturing: What Are the Differences?

While subtractive and additive manufacturing may produce similar results, the production steps and the entire process are distinct. Below, we examine key differences between the two manufacturing processes under the following headings.

Achievable Design

Both manufacturing processes, subtractive and additive, are suitable for achieving simple and intricate design details. Regardless of design complexities and geometries, either process suits your fabrication. Just ensure you use the most appropriate methods between the different subtractive vs additional manufacturing processes for your part. 

However, the subtractive processes are better suited and more straightforward for simple designs. In like manner, AM may be better for complex designs, especially low-volume production, but subtractive manufacturing edges it when dealing with bulk-volume.

Precision and Dimensional Accuracy 

Again, both processes are suitable for creating parts with high precision and dimensional accuracy. However, the subtractive processes are better suited for achieving strict tolerance, extreme precision, and accuracy specifications. In fact, after 3D printing some components, machining operations serve as post-finishing options to build on the part’s tolerance.

Material Selection 

Regarding the comparisons between subtractive vs additive manufacturing, both techniques are compatible with extensive material options. However, subtractive processes edge it, as various materials – thermoplastics, thermosets, resins, metals, alloys, composites, glass, wood, ceramic, etc., suit machining operations.

In contrast, material selection in additive manufacturing is often limited to plastic polymers and their derivatives. However, they are also suitable for fabricating ceramic, metal, and biochemical parts.

Surface Finishing Options

Secondary operations like surface finishing are another critical factor to consider in this comparison between subtractive manufacturing vs additive. Generally, additive processes often require surface finishing because of the unique manufacturing process. There tend to be remains – powder residues and visible deposits – on the layers of the manufactured parts. These deposits may diminish the aesthetics of the component.

Therefore, there is a need for curing, cleaning, or polishing these surfaces to enhance their appearance. On the other hand, subtractive processes, such as machining, create parts with smooth surface finishes. In fact, manufacturers sometimes leave these parts as finished, requiring no further secondary finish.

Manufacturing Cycle Times

Regarding the production cycle times, subtractive manufacturing takes longer than additive manufacturing, especially for single-part and small-scale fabrication. AM or 3D printing is the ideal method for rapid prototyping because it fabricates parts quickly. Subtractive manufacturing often takes time through multiple machine setups and tool changing, especially for complex parts.

However, the factors that elongate the production cycle times in subtractive manufacturing become almost negligible for large-scale production. In machining, for example, the device creates parts simultaneously (batch processing). Therefore, the same time for machine setup, tool changing, and other parameters that increase production times. However, in the case of 3D printing, each part is fabricated singly, layer by layer – this makes subtractive manufacturing better for bulk-volume fabrication.

Material Wastage

Subtractive manufacturing involves removing components of a workpiece to create the desired shape of a part. Therefore, waste production is almost unavoidable. On the other hand, additive manufacturing creates components from powdered materials in layers till the intended size and shape are achieved. Therefore, there is little to no material wastage in this operation.

Production Volume

When we discussed the manufacturing cycle, we have already established that subtractive manufacturing processes are more reliable for bulk volume production. However, additive manufacturing benefits low to medium-volume fabrication.

Customization

Both subtractive and additive manufacturing purposes suit the customization of parts. However, additive manufacturing techniques are the better choice because of the layer-by-layer building of components. However, depending on the subtractive process used in part fabrication, cutting tools may experience some constraints, limiting the customization potential of the process.

The table below summarizes the differences between subtractive vs additive manufacturing.

Which is More Expensive: Subtractive or Additive Manufacturing?

Determining which is more expensive between subtractive vs additive manufacturing processes involves considering factors influencing the overall manufacturing costs. Below, we examine some of them.

Cost of Material

The cost of materials may vary depending on the choice of material for a particular fabrication. However, the powders and filaments for additive manufacturing are generally more expensive than the solid blocks used for subtractive manufacturing purposes. Different factors account for this variation. However, as a general rule, the cost of material per weight using additive manufacturing may be up to eight times the price of the same material for subtractive manufacturing.

Tooling and Machinery

Either manufacturing process incurs significant initial setup costs to acquire the machinery; both are capital intensive. However, machinery for subtractive processes is generally more expensive than additive processes. Moreover, your fabrication may require more specialized manufacturing tools depending on design specifications. 

In contrast, a single 3D printer may suit the fabrication of vast components, considering it builds explicitly the structure in layers. Therefore, the tooling and machine costs are relatively higher for machining.

Energy Utilization 

Both subtractive and additive manufacturing processes are energy-consuming, requiring electricity to power their machines. The energy consumed may vary depending on the fabrication, design complexity, and machining time. However, subtractive manufacturing processes are generally more energy-consuming than 3D printing. 

Operator Skill Level

Either manufacturing processes require skilled labor to operate the machines to ensure the fabrications meet all design specifications. However, most of the operations of these devices are automated; hence, there are fewer labor requirements. Therefore, you need more of an overseer and someone who understands the machines and can troubleshoot or modify the design if required. Therefore, there’s no specific distinction in the operator cost.

Surface Finishing and Post-processing 

The secondary operations your parts require also influence the overall manufacturing costs. Again, this varies on the selected finishing and the number of post-processing operations your parts need. However, we have already established that additive manufacturing often requires post-processing operations.  

Applications of Subtractive vs Additive Manufacturing

Both subtractive and additive manufacturing processes have become a mainstay in various industries, offering vast applications. Below, we examine some of them.

Applications of Subtractive Manufacturing 

We already emphasized the suitability of this process for bulk-volume fabrication. The following include its main industrial applications.

• Automotive Parts: Subtractive manufacturing is the go-to process for creating various car parts. This includes car engines, transmission components, car bodies, chassis, and brake systems, among other fundamental car parts.
• Aerospace Parts: Machining operations are typical for creating parts, like engine parts, landing gear components, avionic housing, control components, etc., for the aerospace industry.
• Tooling Fabrication: CNC machining is a standard technique for creating tools and machine parts for various machinery, including molds and die cavities for injection molding and die casting.
• Surface Fabrication: Because of the versatility of subtractive manufacturing processes, it is used to create contoured profiles, internal pockets, undercuts, etc., which benefit industrial manufacturing. 
• Medical Devices: Subtractive manufacturing methods are suitable for creating various medical instruments. This includes implants, surgical equipment, prosthetics, and even enclosures and parts of high-precision medical gadgets.
• Consumer goods and electronics: Furniture components, kitchen utensils, home decor items, lighting fixtures, electronic housings, etc.

Application of Additive Manufacturing

Below are the main applications of this technique. 

• Rapid Prototyping: creation of iterative designs for testing and product development purposes
• Jewelry Production: 3D printing is suitable for creating intricate designs for the jewelry industry that may be challenging for conventional manufacturing processes.
• Architectural Models, Electromechanical, and Robotic Systems. The process is suitable for creating almost anything you can visualize, regardless of complex and intricate detailing.
• Medical Implants: Additive manufacturing is suitable for creating generalized, customized, and patient-specific medical implants. This includes dental components, hips and knee replacements, etc.
• Other applications include 3D model fabrication, creating parts for the aerospace industry, customized footwear, electromagnetics, 3D electronics, etc.

Conclusion

Meanwhile, subtractive vs. additive manufacturing processes are distinct, even in how they create objects. Both technologies have vast capabilities, making them popular for various manufacturing purposes.

Indeed, both processes can create almost anything you can visualize. However, they have their specialties, as well as their shortcomings. Therefore, you should stick to the one that best suits your project.

For example, when manufacturing parts with strict tolerance and precision requirements, subtractive processes are your best bet. In contrast, when starting a new fabrication, you must test your design suitability and capabilities. In this case, you require the rapid prototyping attributes of additive manufacturing. 

Zintilon’s Expert Subtractive and Additive Manufacturing Services 

Understanding the difference between subtractive vs additive manufacturing services is critical to making the right choice for your fabrication. However, these devices are expensive and may be challenging to acquire.

Therefore, partnering with a service provider is your best bet. Zintilon is an expert service provider of various subtractive and additive manufacturing techniques. Our facilities boast the latest machines with engineers and technicians to ensure a successful project. 

Contact us today for your subtractive and additive manufacturing services. 

FAQs

Is CNC Additive or Subtractive?

CNC machining is a prominent subtractive manufacturing technique. The devices are equipped with various cutting tools for specific machining operations.

Which is More Eco-friendly: Subtractive vs Additive Manufacturing?

Additive manufacturing is more eco-friendly because it produces almost no waste. In contrast, subtractive manufacturing typically generates waste, as it removes components of a workpiece.

Which is Better: Subtractive vs Additive Manufacturing?

This question has no specific answer, as each is a valuable manufacturing space method. Just ensure to stick to the one that best suits your project. However, since the world is tilting towards conservation and sustainability, additive manufacturing might be the way forward since it creates minimal waste.