What is 3D Printing?

What is 3D printing? How does it work? What makes it different from other manufacturing techniques? The answers to these questions may surprise you. There are several types of 3D printing technologies. While all of them build parts layer by layer, they differ significantly in terms of technology, supported materials, printable part size, as well as the accuracy, resolution, and precision that can be achieved by the 3D printer.

Although 3D printing is one of the most well-known manufacturing methods, it is not the only additive manufacturing technique. Additive manufacturing itself can be divided into seven different processes. Injection molding and thermoforming can also be considered forms of additive manufacturing because they add rather than remove material. Therefore, all additive processes (including 3D printing) are fundamentally different from subtractive manufacturing.

As the name suggests, subtractive manufacturing removes material from a pre-formed block, rod, sheet, or extrusion to create a component. Examples of subtractive manufacturing include machining, milling, turning, laser cutting, and waterjet cutting.

Additive & Subtractive Manufacturing

Now that you understand the basics, it becomes clear that the difference between 3D printing and other manufacturing methods is not simply additive versus subtractive manufacturing. So how do the different types of 3D printing work, and what else makes 3D printing different from other manufacturing techniques? More importantly, why do designers use 3D printing instead of traditional manufacturing methods—not only for prototyping but also for end-use products? Let’s explore further.

How Does 3D Printing Work?

3D printing is named as such because it uses a process similar to a traditional inkjet printer, but instead of printing on paper, it creates three-dimensional objects. This approach removes many traditional design limitations, such as the inability to create freeform geometries or lattice structures.

The first step in any 3D printing process is designing a model using computer-aided design (CAD) software. These 3D models can contain highly detailed features that are often difficult to achieve using traditional manufacturing methods.

Once the 3D model is completed, it must be sliced into individual layers, each containing instructions for the 3D printer. The model is typically exported as an .STL file, while the toolpath instructions are generated in .gcode format. Most CAD software can generate .STL files, which describe surface geometry using triangles and a 3D Cartesian coordinate system.

During the printing process, each horizontal layer is built one on top of another to form the final object. While the build mechanisms vary depending on the technology, the following are some of the most common 3D printing technologies:

• Stereolithography (SLA) uses a laser to photopolymerize liquid resin.
• Digital Light Processing (DLP) is similar to SLA but uses a projected light source.
• Selective Laser Sintering (SLS) uses a laser to fuse powder materials.
• PolyJet builds components by jetting droplets of photopolymer onto a build platform and curing them.
• Direct Metal Laser Sintering (DMLS) uses heat sources and metal powders.
• Electron Beam Melting (EBM) uses a high-energy electron beam to melt powdered metal.
• Fused Deposition Modeling (FDM) continuously extrudes thermoplastic filament material.

As you may notice, some of these technologies are designed specifically for plastics, while others are intended for metals. There are also specialized variations developed for unique applications.

For example, Projection Micro-Stereolithography (PµSL) is a form of SLA that uses flashes of ultraviolet (UV) light to rapidly photopolymerize entire layers of resin. An example of this technology is the Boston Micro Fabrication (BMF) microArch System, which supports continuous exposure for faster processing and can produce microscale components with extremely high accuracy, precision, and resolution.

How 3D Printing Differs from Other Manufacturing Techniques

As discussed earlier, the difference between 3D printing and other manufacturing techniques is not simply additive versus subtractive manufacturing. It is also not merely about the use of CAD software, 3D modeling, or digital manufacturing. Many traditional manufacturing methods already incorporate advanced computer-aided manufacturing (CAM) technologies, making the distinction between “traditional” and “modern” manufacturing overly simplified.

Ultimately, the key difference lies in how 3D printing builds parts layer by layer and enables greater design freedom. From wall thickness optimization and topology optimization to lattice structures, design for manufacturing (DFM) becomes fundamentally different with 3D printing. This additive manufacturing method also enables the production of single-piece components instead of assemblies requiring multiple parts and fasteners.

There are also specific comparisons between 3D printing and individual manufacturing processes. For example, 3D printing is not the only tooling-free manufacturing process, nor is it the only option for low-volume production. Waterjet cutting also eliminates tooling requirements, while urethane casting with silicone molds can produce low-volume parts as well. However, because 3D printing is tooling-free, it removes the costs and lead times associated with molds and tooling.

Importantly, the distinction between 3D printing and other manufacturing techniques is not simply about prototyping versus production. While 3D printing is extremely valuable for prototyping, many 3D printed objects can also function as end-use parts. Post-processing may still be required, but surface finishing is common across many manufacturing methods, especially machining.

Additionally, just as not all CNC machines are capable of processing extremely small components, not all 3D printers can manufacture microscale parts.

Finally, 3D printing differs from other manufacturing techniques in terms of material capabilities. For example, although BMF’s PµSL 3D printers can use some of the same polymers as injection molding, the resulting printed materials do not necessarily have identical properties. However, PµSL technology can also process biocompatible resins and ceramics—materials that most injection molding systems cannot handle. BMF’s PµSL printers also support an Open Material System, allowing designers to print using the materials best suited to their applications.

Learn more about 3D printing technologies such as BMF PµSL and other advanced 3D printers, and discover how the right technology can help simplify manufacturing processes and support various industrial applications.