How does 3D printing work? How is it different from other manufacturing techniques? The answers to these questions might surprise you. For starters, there isn’t just one form of 3D printing. Rather, there at several different types. 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 they support, the part sizes they can produce, and the accuracy, resolution and precision that 3D printers can achieve.
Also, although 3D printing is a well-known type of additive manufacturing, it isn’t the only additive manufacturing technique. EWI, a non-profit organization formerly known as the Edison Welding Institute, divides additive manufacturing 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.
No matter which forms of manufacturing you include, all additive processes (include 3D printing) are inherently different from those that remove material in order to produce a part. Examples of subtractive manufacturing include machining, milling, turning, laser cutting, and water jet cutting. Despite the differences between them, none of these individual manufacturing techniques build parts in layers. Instead, they remove material from a pre-formed piece such as a block, bar, sheet, or extrusion.
Now that you understand a few basics, it’s clear that the differences between 3D printing and other production methods aren’t just about additive manufacturing vs. subtractive manufacturing. So, how do the different types of 3D printing work, and what else makes 3D printing different from other manufacturing techniques? For that matter, why are designers using 3D printing instead of traditional manufacturing methods – and not just for prototyping? The following sections explain.
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 difficult 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.
- Multi jet fusion (MJF) is a powder-based process that does not require a laser.
- 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. PµSL 3D printers from Boston Micro Fabrication (BMF) 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 you’ve read, the difference between 3D printing and other manufacturing techniques isn’t just about additive vs. subtractive manufacturing. But it’s not about the use of CAD software, 3D modeling, or digital manufacturing either. Many other production methods use forms computer-aided manufacturing (CAM), and distinctions such as traditional vs. modern manufacturing are overly simplistic. Today, well-established manufacturing techniques such as molding and machining can be highly sophisticated.
Ultimately, the difference between 3D printing and other manufacturing methods is about 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 tool-less 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 tool-less 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 for their choice.
To learn more about how PµSL technology works and how it can support your application, contact BMF.