Differences Between 3D Printing And Other Manufacturing Techniques

What is 3D Printing?

What is 3D printing? How does it work? How is it different from other manufacturing techniques? The answers to these questions might surprise you. There at several different types, and there isn’t just one form of 3D printing. They all build parts by depositing material one layer at a time, but there are important differences in terms of 3D printing technologies, the materials supported, the part sizes that can be produced, and the accuracy, resolution, and precision that 3D printers can achieve.

Although 3D printing is a well-known type of additive manufacturing, it isn’t the only additive manufacturing technique. Additive manufacturing can be divided into seven different processes, none of which is simply called “3D printing”. Injection molding and thermoforming are also forms of additive manufacturing in the sense that they add rather than subtract material. As such all additive processes (including 3D printing) are inherently different from subtractive manufacturing. As its name implies, it is the process that removes materials from a pre-formed piece such as a block, bar, sheet, or extrusion to produce a part. Examples of subtractive manufacturing include machining, milling, turning, laser cutting, and water jet cutting.

Understanding the fundamentals reveals that the distinctions between 3D printing and other production methods go beyond merely additive versus subtractive manufacturing. To gain a comprehensive understanding, it is essential to explore the various types of 3D printing technologies and their unique functionalities. Additionally, it is important to examine what differentiates 3D printing from other manufacturing techniques. Furthermore, we need to consider why designers increasingly favor 3D printing over traditional manufacturing methods, extending beyond mere prototyping applications. Let's delve deeper into these aspects

How does 3D printing work?

3D printing is so named because it uses techniques that are similar to those of traditional inkjet printers but to produce three-dimensional parts that eliminate traditional design constraints, such as the inability to produce freeform shapes or lattice structures. The first step in any 3D printing process is modeling with computer-aided design (CAD) software. These 3D models can have varying levels of detail, including fine details that traditional forms of manufacturing either cannot or having difficulty achieving. 

After the 3D model is created, it needs to be sliced into individual layers, each of which contains values with instructions for the 3D printer. Each layer is an .STL file but the tool path itself is in .gcode. Most CAD software can output .STL files, which describe surface geometry using triangles and a 3D Cartesian coordinate system. During 3D printing, single horizontal layers are built one on top of the other to produce the final object. Build mechanisms vary, but these are the major 3D printing technologies. 

  • Stereolithography (SLA) uses a laser to photopolymerize a liquid resin.
  • Digital light processing (DLP) is similar to SLA but uses a projected light source .
  • Selective laser sintering (SLS) uses a laser to sinter powder.
  • PolyJet builds parts by jetting photopolymer droplets onto a build platform and solidifying them.
  • Direct metal laser sintering (DMLS) uses a heat source and a bed of metal powder.
  • Electron beam melting (EBM) uses a high-energy beam of electrons to melt powdered metal.
  • Fused deposition modeling (FDM) extrudes a continuous filament of thermoplastic material.

As you can see, some of these technologies are only for plastics and some are only for metals. There are technology variants for specialized applications.  For example, projection micro-stereolithography (PµSL) is a form of SLA that use a flash of ultraviolet (UV) light to rapidly photopolymerize an entire layer of resin. An example of PµSL 3D printers,  Boston Micro Fabrication (BMF) microArch Systems support continuous exposure for faster processing and can produce microscale parts with high accuracy, precision, and resolution.

How is 3D printing different from other manufacturing techniques

As previously discussed, the differences between 3D printing and other manufacturing techniques extend beyond the simple dichotomy of additive versus subtractive manufacturing. Furthermore, it is not solely about the use of CAD software, 3D modeling, or digital manufacturing. Many other production methods also employ computer-aided manufacturing (CAM) technologies, and distinctions such as traditional versus modern manufacturing are overly simplistic. Established manufacturing techniques, such as molding and machining, have evolved to become highly sophisticated and advanced

Ultimately, the difference between 3D printing and other manufacturing methods is how 3D printing builds parts in layers, and how 3D printing provides greater design freedom. From thickness and topology optimization to lattice formation, design for manufacturing (DFM) is different with 3D printing. This form of additive manufacturing also enables the design of single-piece parts instead of assemblies that require multiple components and fasteners. 

There are also comparisons between 3D printing and other individual manufacturing processes that can be made. For example, 3D printing is not the only toolless manufacturing process, and it’s not the only option for low-volume manufacturing. Water jet cutting also eliminates the need for tooling, and urethane casting with silicone molds can also be used to produce low volumes of parts. Because it is a toolless process, however, 3D printing eliminates the costs and wait times associated with molds and tools. 

Importantly, the difference between 3D printing and other manufacturing techniques isn’t about prototyping vs. production either. Although 3D printing is especially useful for prototyping, some 3D printed objects can be used as functional end-use parts. Post-processing may still be required, but surface finishing is typical with many forms of manufacturing, especially machining. Just as not all CNC machines can process small parts, however, not all 3D printers can produce parts at the microscale. 

Finally, 3D printing is different from other manufacturing techniques in terms of materials. For example, although BMF’s PµSL 3D printers can use some of the same polymers as injection molding, these 3D printed materials do not have identical properties. Yet, PµSL technology can also 3D print biocompatible resins and ceramics, materials that most injection molding equipment can’t process. PµSL 3D printers also work with BMF’s Open Material System so that designers can print with the material of their choice. 

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