Since the early 2010s, there has been a significant rise in the usage of 3D printing, also known as additive manufacturing, across a variety of industries. This has been driven by access to 3D printing services, desktop printers, and easy-to-learn 3D modeling tools. The barrier to entry is significantly lower than other manufacturing methods because 3D printing only requires a CAD (computer aided design) model and is relatively unrestricted by traditional manufacturing design rules.
Differences Between Additive and Subtractive Manufacturing
It is important to know what processes are defined as 3D printing to understand why some of these advantages exist.
Additive manufacturing (AM) is an umbrella term for a method of making parts by joining materials, usually layer by layer, using a 3D model as a guide. For example, laser powder bed fusion processes, like Selective Laser Sintering, create parts by etching a cross-section profile of the model into a heated powder bed. Then, the level bed is shifted down, a new layer of material added to the surface, and the etching continues. In other cases like material extrusion, which includes Fused Deposition Modeling, a heated polymer filament is extruded and zig-zags to the shape of a cross-section. This process is then repeated for each layer until the part is formed. This contrasts with subtractive manufacturing, where a large stock piece is shaped, cut, or formed through a die to create the part. The most common example is machining, where a bar or rod stock piece is cut using endmills, drills, and other cutting tools to create a final shape. Machining can also produce tooling used for the injection molding process.
Advantages of 3D Printing
Just like traditional manufacturing, 3D printing processes each have unique strengths and trade-offs. The advantages listed below, however, are generally true for all types of 3D printing.
- Speed: After platform set-up, most parts can be manufactured in less than a day. Sometimes, part production can even take less than an hour. The agility of 3D printing is largely due to its simplified setup, which only requires build preparation software rather than machine setup required by traditional machining.
- Affordability: For both AM and traditional manufacturing, the overall cost of a part results from both material costs and machining time. However, with 3D printing, there are no costs related to machine setup and finishing as in traditional manufacturing. For subtractive manufacturing, these include material procurement, programming tool paths, configuring a setup, running and monitoring the machine, and any finishing work like deburring or sanding. With injection molding, these costs are even more of a factor due to costly tooling required before any parts can be made. None of these costs are present with AM, resulting in considerably cheaper parts.
- Just-in-time inventory: Additive manufacturing allows you to create and stock parts on demand. This means parts and products made with AM never have to be made in surplus. They can simply be made, shipped, assembled, and sold as needed. Businesses can benefit from more efficient production, where no money is wasted on overstocking a product or part.
- Purpose-driven designs: When designing for traditional manufacturing, the designer must make concessions for manufacturability and cost reduction. Functional features often need to be adjusted to allow for production. The “optimal” design is often impossible to manufacture with traditional means. With AM, this is not the case. In fact, many new design opportunities exist for making all-in-one, topology-optimized, and lightweighted parts via additive manufacturing.
- Click-and-go sourcing: Additive manufacturing is much simpler to source than traditional machining, often via online pricing systems like Xometry’s platform. With 3D printing, a part’s outcome is dictated by the selected process and part parameters. In just a couple of drop-downs, a project can be ready to order without the need for detailed engineering prints.
- Snapshot prototyping and design validation: With the decreased time to manufacture, and less stringent design restrictions, AM allows designers to rapidly design and iterate on their prototypes. With traditional manufacturing, it can take weeks to get a physical prototype in your hands. With AM, you can often have a part in hand within the week. This allows designers and engineers to test and change their ideas on the fly. Ultimately, a new product move to production much more quickly. A good analogy is moving from film to digital cameras. In the past, you had 24 shots on the camera and you would be more selective on if and when to take pictures. With digital, you can take thousands of pictures with almost no cost and ultimately let you choose the best out of those options, resulting in a better product.
- Mass customization: 3D printers can produce multiple parts with multiple configurations, often in a single build and with no additional setup costs. For example, BMW’s MINI Yours Customized lets customers create personalized vehicle trim and other features via 3D printing. With traditional processes, this would require high-cost tooling per design. The ability to selectively configure parts, combined with 3D printing, allows companies to target finer consumer segments with customized products.
- Complexity without increased cost: CNC machining and injection molding impose strict limitations due to the requirements of the cutting tools and direction of pull. As parts get more complex, the cost to manufacture can skyrocket. With additive manufacturing, the cost is not affected by increased complexity, thus unshackling the budget-burdened designer and enabling them to design more purpose-driven parts.
- 3D printing advances CAD software: This has been one of the most interesting feedback loops since the low-cost desktop 3D printer came out. Initially, many purchased a printer and realized all CAD software was expensive and that the feature sets were not well equipped for 3D printing. In turn, over the last decade, there has been an entire industry created around accessible CAD software, which is often free or extremely inexpensive but still comparable to professional CAD software. Additionally, professional CAD software has added features like 3D printing design evaluations, print setups, and even texturing.
Disadvantages of 3D printing
- Surface finish: Because 3D printed parts are typically built layer-by-layer, they often show visible steps on the vertical surfaces. Depending on the processes, these layer heights can be significant, making the product less aesthetically pleasing to consumers. Although there are some post-processing technologies that can remedy uneven surfaces, the natural surface finish of a print is still far from the smooth, continuous surfaces produced by traditional processes like injection molding or machining.
- Variation in machines and parameters: Not every printer is equal. For example, desktop 3D printers are often kit-built and hand-tuned. Even more “prosumer” printers can have inconsistencies from print-to-print or between material changes. Because of this, there can be high variability if, for example, an ABS part was requested from multiple individuals. Companies like Xometry can provide consistency from part to part, since they use high-end industrial 3D printers with OEM-driven machines, materials, and parameters to provide a consistent product.
- Limited material selection: Although the list keeps growing, the materials available for 3D printing, particularly on the professional/industrial level, are measured in the dozens. Compared to the thousands of purchasable materials on the market, particularly for injection molding, this offering is slim. In parallel with the growth of 3D printing, many standards are being improved to streamline the process for defining and qualifying materials for additive manufacturing.
- Size limitations: It is difficult for 3D printing platforms to produce parts that are smaller than a peanut and larger than a soccer ball. For example, DMLS metal 3D printing typically has a platform of 9” maximum extent. Although larger platforms exist, they are not widely available. The larger the part, the less availability there is of printers as well as materials to print at that scale. Similarly, for ultra-small 3D print sizes, specialized printers are required and are more difficult to source.
- Sub-optimal for mass production: 3D printing technology still tends to max out in value in the low hundreds range. After that, many traditional technologies like injection molding or casting can become more economical. The advantage of 3D printing is, instead,consistency between prints from the same platform and parameters. Because setup is digital, mass production may be adapted in the future to come from multiple suppliers instead of a single, low-volume supplier.
3D printing is a great tool for building on-demand parts, accurately rendering purposeful features, and reducing significant upfront barriers to manufacturing. However, 3D printing works best in a marketplace with traditional manufacturing, where the two types complement each other depending on the individual project requirement. Innovations like Xometry’s AI-driven MaaS platform, as well as advancements in additive technologies, enable more flexibility in design, materials, and production for custom manufacturing.