We recently posted a blog on the various ways that CNC Machining currently kicks 3D Printing's butt. However — as a Digital Manufacturing company that offers both technologies — it's only fair that we spend a few moments explaining how and why 3D Printing crushes CNC Machining. We will examine this point on the grounds of organic geometries, internal features, lattice structures, one-offs, and mass-personal customization.
Both 3D Printing and CNC Machining are driven by CAD files. As a result, generating tool paths can be largely automated for both processes. That being said, 3D Printing excels at creating organic geometries — curved surfaces, high degrees of complexity, and similar builds. CNC machines generally struggle with gently arcing surfaces, requiring extra time and tool changes to deliver this complexity. On the contrary, due to the additive nature of 3D Printing, the issue of including additional detail during the manufacturing process is almost of no temporal consequence.
3D Printing can uniquely deliver internal features in its build parts. With CNC machines, the tool needs access to the feature to be machined. As a result, the interior areas of CNC parts are filled and solid; hollow only when machining two or more pieces that will be welded together in a post-process. The additive nature of 3D printers, on the contrary, simply skips the vacant areas during the phase of deposition. A notable exception to this rule is the requirement for internal support structures in certain hollow designs.
Another feature that 3D printers can deliver is the lattice structure. These builds are generally impractical to machine and, when they are internal to a part, feasibly impossible. 3D Printing is basically the perfect lattice building technology. Because these processes place materials layer by layer in mostly any location, they're able to build up lattice structures and customize their shape to deliver particular performance characteristics like stiffness, elasticity, or failure modes.
CNC Machining and 3D printing are the two leading technologies when it comes to one-off designs. Both are driven by CAD files and are capable of creating singular parts with relative ease — compared to the tool creation required by casting an injection molding technologies. However, 3D Printing generally gets the nod when it comes to one-off production. While machining generally does not require the creation of tools, there are circumstances when custom fixtures need to be created for a machined part to allow for the machinist to access all relevant features of a design. In contrast with this, 3D Printing is a completely tool-less technology; simply fit in a design and get an output. As noted previously, the output may have supports that require a degree of post-processing effort, but nevertheless, a single unit comes very easily from a 3D Printing process.
Mass Personal Customization
Following on two of the earlier points about organic geometries and one-offs, 3D printers outperform CNC machines in the domain of mass personal customization. There is a strong trend toward providing customers unique opportunities to customize products that meet their very personal needs. This is especially notable in the medical field when we talked about custom orthodontics, teeth aligners, and more. When it comes to these sorts of applications, 3D Printing definitely crushes CNC Machining. Because 3D Printing delivers an extreme variety of different geometries, with limited care to the complexity or geometry at hand, even at quantities of one, it has emerged as a leading tool for mass personal customization. You need only look to the success of Invisalign or Smile Direct Club as examples of 3D Printing's ability to deliver mass personal customization.
A last area where 3D Printing outperforms CNC Machining is in inventory flexibility with regards to raw stock. CNC Machining requires a workpiece from which the design is carved away. This is one reason why blocky shapes tend to be better suited for CNC Machining. You simply need to chip away a little bit of material and you will arrive at your end part. With CNC Machining, however, you need raw stock that is in the shape of your final product to be economically viable. If your part has an extremely high scrap ratio, which is to say that you are carving away a lot of excess material from your starting work piece, the project can become highly uneconomical for your business. As a result, you need to have the right raw stock pieces to deliver CNC parts economically; and if you work with a wide variety of different parts, you need to stock a variety of material options to be efficient with your machine. In contrast, 3D printers are immensely flexible when it comes to their manufacturing process. Generally speaking, 3D printers operate off of filament or powder inputs that are basically one-size-fits-all. A highly condensed container of powder or filament can be delivered and stocked, and that in turn can create basically any geometry.
3D Printing outperforms CNC Machining on a wide variety of applications and use cases. As we touched on today, 3D Printing crushes CNC in many cases, but just as CNC Machining kicks 3D Printing's butt in its own universe of applications. It's all a matter of use and — thankfully at 3Diligent — we are capable of supporting you with whichever path you choose to go down.