Traditional vs. Additive Manufacturing

All stakeholders in the industry sector are always seeking to improve manufacturing techniques to lower production costs, increase the quantity and quality of finished products as well as expand the capabilities of their factory facilities. In this article, we’ll explore the differences between two manufacturing processes- Traditional and Additive Manufacturing- that are widely used across all industries.

What is Traditional Manufacturing? 

Traditional manufacturing, also referred to as standard or conventional manufacturing, usually refers to subtractive and long-established technologies that remove layers of material from a workpiece or block of stock material, in order to obtain custom-designed products.

Traditional manufacturing entails four common technologies, namely:

A) Machining: This production method is mainly used to manufacture metal products, but it’s also common for the production of low to mid-volumes of plastics. It’s known for producing shapes with very high precision and good accuracy, though it tends to waste material in form of removed chips. Common machining technologies include turning, drilling, milling, and laser cutting.

Recently, the advent of 5-axis CNC machining has considerably improved the efficiency of subtractive machining technologies. CNC stands for Computer Numerical Control. While CNC machining is a traditional manufacturing process in which pre-programmed computer software regulates the movement of machine tools. With 5-axis or 3-axis, CNC machining, three-dimensional (3-D) cutting tasks can be performed in a single set of prompts.

B) Injection Molding: This traditional manufacturing process makes use of a designed mold, as parts are produced by injecting molten material into the already created mold. It is extremely useful for the large-scale production of parts from a thermoplastic polymer material. Generally, approximately 80% of the durable plastics we use in our everyday lives are manufactured through plastic injection molding. Other principal molding techniques for high-volume production of thermoplastics include rotational and compression molding.

C) Forming: This technology is only used to manufacture hollow-bodied and thin-walled parts, as it involves pressing heated thermoplastic sheets on custom dies. Air/vacuum pressure and male plugs are then utilized to form the sheet into its final shape. Plastic forming is the choice manufacturing process for parts and prototypes in the packaging industry, with thermoforming technology being widely utilized in shaping polymers.

D) Joining: This process involves the joining of semi-finished parts. It thus allows the construction of complex assemblies from simpler components. Since the joining procedure is often defined by the manual work performed by a human operator, the process is ideal for small to mid-scale production. Examples of joining techniques include fastening, welding, and adhesive bonding.

What is Additive Manufacturing? 

Additive Manufacturing (AM), also known as Additive Layer Manufacturing (ALM), works by assembling or depositing materials layer by layer to form the desired physical object. AM was first developed in the 1960s, and ever since it has seen rapid and continuous growth, leading to the emergence of novel additive techniques that expand manufacturing capabilities. Today, all high-volume implementations of additive layer manufacturing utilize high-throughput 3D printing processes.

3D printing is a computer-controlled additive manufacturing technology used to generate three-dimensional (3-D) objects through sequential-layer material addition. This process can fabricate parts and assembled products with greater accuracy that meets the product specifications. 3D printing technologies are categorized as either Direct or Indirect 3D printing. In the direct process, the product design is made directly during the 3D printing process. While in the indirect process, the user has to create a design model to be used by the 3D printing equipment.

Common 3D printing technologies utilized in additive manufacturing include:

A) Powder Bed Fusion (PBF): This method uses a heat source, usually an electron or laser beam to selectively melt/sinter and join together powdered material layer by layer. It can be used with both polymers and metals, making it one of the most popular 3D printing processes used for additive manufacturing (AM) in industries.  

B) Material Extrusion: This manufacturing technique makes use of spooled polymer materials that are either drawn-out or extruded via a heated nozzle that is mounted on a movable robotic arm. A motor is used to drive the nozzle horizontally and the printing bed vertically, thereby creating a melted material layer by layer. The layers adhere together using chemical bonding agents or through temperature control. Fused Filament Fabrication (FFF) and Fused Deposition Modeling (FDM) are the most popular material extrusion processes. 

C) Directed-Energy Deposition (DED): This technique uses a focused energy source, usually a Plasma Arc (PAW), Electron, or Laser beam to melt or sinter coaxial feedstock material of wire or powder. The melted or sintered material is simultaneously deposited on a substrate through a nozzle. This method is mainly used to process metals such as stainless steel, aluminum, copper, or titanium in powder form or as wires.

D) Sheet Lamination: With this methodology, thin sheets of stock material supplied through a system of feed rollers are joined together layer-by-layer to form a complete piece, which is then cut into a 3-D object. Examples of sheet lamination processes include Laminated Object Manufacturing (LOM) and Ultrasonic Additive Manufacturing (UAM).

E) Binder Jetting: This process uses a binding agent and a powder-based material. An industrial print-head is then used to selectively deposit the binding agent (in liquid form) onto a thin layer of powder particles- ceramics, composites, metals, or foundry sand. The process is carried out repetitively by depositing material layer by layer to come up with high-value and customized parts and tooling. The binder is used as the adhesive agent between the powder layers.

F) Selective Laser Sintering (SLS): This technique uses a high-power laser beam to sinter small particles of powered polymer material (usually polyamide or nylon), into a solid structure that’s defined by a 3D model. 

G) Vat Photopolymerization: In this 3D printing process, a liquid photopolymer resin placed in a container or vat is selectively cured (hardened) by ultraviolet (UV) light. As the resin turns into solid, a 3D platform moves downwards to print the desired object layer by layer. The two most common types of vat photopolymerization process are Digital Light Processing (DLP) and Stereolithography (SLA). SLA 3D printers use a point laser to cure the photopolymer resin, while DLP 3D printers use the voxel approach for the same.

Differences between Traditional and Additive Manufacturing 

The differences between additive and traditional manufacturing aren’t especially clear. For that reason, in this section, we’ll discuss the most notable features that differentiate the two methods.

A) Physical Characteristics: Traditional manufacturing involves the use of subtractive processes in which layers of materials are removed from a workpiece to construct the desired part. While additive manufacturing processes add layers of material (layer-by-layer) to create the final object. Also, most of the materials used for 3D printing do compete with those used in traditional manufacturing, in terms of strength and durability.

B) Production of Complex Geometries: End-user products made using traditional manufacturing processes must always adhere strictly to the rules of Design for Manufacturing (DFM). DFM is a process of efficiently designing or engineering a product during the design stage, in order to reduce the manufacturing costs to be incurred. DFM rules discourage the production of parts with complex geometries, as this is likely to result in unnecessary additional costs.

However, additive manufacturing using 3D printing technologies eliminates this concern. As with 3D printing you can develop complex designs and produce complex geometries without any additional costs. In fact, any design that would be impossible with traditional manufacturing techniques can be achieved with 3D printing, if the right support material is available. But there are other 3D printing technologies like Selective Laser Sintering (SLS) which do not require any form of support material. Instead, the leftover un-sintered powder is used as the self-supporting material for that process.

Hence, additive manufacturing processes can produce extremely complex geometries more efficiently than conventional manufacturing methods. This capability virtually eliminates all other additional costs associated with creating such complicated designs. For example, 3D printing processes for mass production like SLS, are always identical regardless of the intricacy and complexity of the desired object. As a result, post-processing additional costs are eliminated. In addition, the complex geometries produced through additive manufacturing techniques are more robust and lighter than their conventional counterparts.

C) Material Waste: Traditional manufacturing methods like machining tend to waste a lot of material, as layers of parts are cut off to achieve the desired shape. In contrast, additive manufacturing techniques involve a considerably lesser amount of material waste. For example, with 3D printing, it’s possible to use only the amount of material that’s necessary to create a given part. This ensures that the resulting material waste is very minimal.

D) Assemblies: Additive manufacturing processes like 3D printing allow users to combine the manufacturing and assembling phases into one procedure, in which fully mobile assemblies can be printed. This saves both production time and costs. But with traditional manufacturing, such assemblies can only be produced as separate parts to be assembled later on, which is both costly and time consuming.

E) Custom Designs: Traditional manufacturing processes can be used for mass production of identical products, but they offer little to no room for customizing such products. On the contrary, additive manufacturing can be employed to create highly customized products with less difficulty. 3D printers, for example, have the capability to print objects of any physical configurations from “ground zero” reference, which makes them perfect for generating customized products.

F) Manufacturing Equipment: In general, traditional manufacturing methods require several manufacturing steps, with each step using a different machine/equipment to get the task done. For example, in CNC machining different machine tools such as drilling, milling, and turning are commonly used in unison to produce the final metal component. On the contrary, in additive manufacturing, all production phases can be handled by a single device like a 3D printer.

Also, with 3D printing, labor requirements are significantly reduced compared to traditional manufacturing. This is because 3D printers create components and final products in an entirely automated manner, and the human operator just oversees the manufacturing task. But most traditional manufacturing processes are often defined by the manual work performed by the human operator.

G) Material Selection: Traditional manufacturing techniques provide a higher material selection, as they produce parts from a wide variety of industrial materials including composites, metals, plastics, foam, wood, and glass. Also, some techniques like forming and injection molding can create products from materials with varying physical and chemical properties.

But when it comes to additive manufacturing, 3D printing provides a much sparser material selection. For example, material extrusion techniques like Fused Deposition Modeling (FDM) are limited to thermoplastics that can be extruded. Vat photopolymerization processes like Stereolithography (SLA) are limited to epoxy-based resins and photo-curable acylate. While Selective Laser Sintering (SLS) can only be used to process thermoplastic powder that is machine-specific.

H) Production Quantity: Traditional manufacturing processes like plastic injection molding are best suited for high-volume manufacturing or mass production. This is because it’s not economical to design a mold for a production cycle of just a small number of parts i.e. less than 100 parts. On the other hand, 3D printing in additive manufacturing is more economical for short-run production or low-volume manufacturing.

I) Lead Time and Production Costs: When it comes to manufacturing, industries are most concerned with minimizing manufacturing lead times and incurred production costs. Manufacturing or production lead time is the period between when a customer places an order and when the manufacturer delivers the product.

Generally, traditional manufacturing takes a longer lead time as CAD (Computer-Aided Design) design models and injection molds are sometimes required to facilitate the manufacturing process. And at times, designing and creating a single mold may take up to a couple of months, costing up to thousands of dollars. This means that it can take 15-60 days to produce and deliver a part to a customer, and for that to happen the factory floor where production is taking place must be ramped up to speed.

However, with additive manufacturing techniques like 3D printing, a part can be produced on customer demand and shipped without the need for prior tooling or ramping-up production. This is due to the fact that 3D printing techniques involve depositing material layer-by-layer on a surface or printing bed. And as a result, a shorter lead time of 2 to 3 days can be achieved, while observing a significant reduction in overall production costs as injection molds are not required.

Note: For traditional manufacturing, production costs are usually high but it’s possible to achieve economies of scale through mass production, which leads to low unit costs. But additive manufacturing involves minimal setup costs, and unit costs don’t vary with scale. This is why it is best suited for low-volume manufacturing.

How Does Additive Manufacturing Complement Traditional Manufacturing? 

The choice between traditional versus additive manufacturing doesn’t always have to be binary. As additive manufacturing can complement traditional manufacturing processes in the following ways: 

• Expediting Prototyping: 3D printing can be used to accelerate product prototyping, thereby assisting engineering and design teams to evaluate the functionalities and aesthetic features of a new product. The teams are thus able to experiment with a variety of design choices since multiple prototypes can be generated easily in a single batch using 3D printers. The final product design can then be produced at scale using traditional manufacturing processes, or a combination of the two methods. 
• Part Consolidation: Additive manufacturing stands out in its ability to produce highly complex part geometries. For example, a complex part that is usually produced as multiple separate pieces with traditional manufacturing can be 3D printed as a single part that doesn’t require assembling. Thus, it can be more efficient to 3D print complex parts even for mass production while using traditional processes to manufacture simpler parts.  
• Flexible Manufacturing Capacity: Due to fluctuating market demands for some products, industries can use 3D printing techniques that support multiple products to increase production capacities, in response to sudden spikes in product demand.  

This is possible because a single 3D-printing machine can easily produce a variety of products without tooling, and with multiple machines, a company can quickly scale up into full-fledged additive layer manufacturing operations. Such companies can then implement Just-in-Time inventory and lean manufacturing techniques, rather than holding and managing huge inventory. 

Traditional manufacturing can also complement additive manufacturing depending on the type of materials used. In that, conventional manufacturing processes like machining or joining can be performed on 3D printed parts to achieve very low tolerances, smooth surfaces, or to assemble multiple complex and large parts. In addition, high-quality surface finishes can be obtained using traditional manufacturing technologies like chemical and mechanical polishing. Welding would also be a very good option for joining together two or more 3D printed parts.

This entry was posted on March 28th, 2022 and is filed under Uncategorized. Both comments and pings are currently closed.