Both additive and subtractive manufacturing run through CAD (Computer Aided Design) software, and both forms of manufacturing can be highly precise and used for complex designs across a variety of industries and uses.
Additive manufacturing
The world of additive manufacturing is ruled by 3D printing which, as the name suggests, operates by printing layers of material rather than detracting from pre-existing objects, a feature known as fused deposition modeling. Repeated depositions in the same area by the machine build the final model from the bottom up. So it’s called a 3D printer, and actually prints each layer in 2D cross-sectional layers, which are basically stacked on top of each other until the desired design is produced. It connects materials layer-by-layer from 3D model data, usually by nozzle deposition of material, UV curing or thermal energy. Manufacturing offers four 3D printing technologies: Fused Deposition Modeling (FDM), Laser Sintering (LS), Multi Jet Fusion (MJF) and Direct Metal Laser Melting (DMLM), 3D printing for metal and plastic low-volume production parts Rapid prototyping and fabrication.
Ordinary printers use powder or ink to mark paper, but these are of course not enough substances to build a 3D design. In most 3D printing, each layer is made of molten thermoplastic, which is then fused using adhesives or ultraviolet light. Together. Thermoplastics are plastics whose shape depends on temperature, turning into a liquid when heated and returning to a solid form when cooled. This of course means that during 3D printing, the machine has to wait for each layer to cool before depositing the next in order to maintain the integrity of the shape. The most commonly used material for 3D printing is plastic, but some also use metal. These printers still use the same 2D slice-by-layer process, and they can also use metal powder instead of plastic material.
Subtractive manufacturing
Subtractive manufacturing starts with a piece of material, which is then cut to reveal and create the desired part. CNC machines dominate the field of subtractive manufacturing and come in many forms to meet various needs. Like 3D manufacturing, CNC machining can be used on plastics and metals, but in their solid, original form. CNC machines work in a variety of ways, they can introduce manipulating and rotating tools into stationary material held in place, or the object itself can be rotated by the machine, depending on the project. CNC machines can machine a variety of materials, from metal and plastic to wood, and come in all shapes and sizes.
Plastics commonly used for injection molding and CNC machining have been developed for use with thermoplastic 3D printing techniques such as fused deposition modeling (FDM) and laser sintering (LS). Traditionally machined metals, such as stainless steel and titanium, have been developed for powder metal fabrication using direct metal laser melting (DMLM).
Advantages and disadvantages of both
One of the greatest advantages of CNC machining is its ability to achieve very tight tolerances, typically +/- 0.01 or +/- 0.025mm, whichever is greater. For well designed parts, tolerances of +/- 0.05mm or +/- .005mm can be achieved using Fused Deposition Modeling (FDM) techniques, whichever is greater, CNC machining is the best fabrication if tolerances are a priority choose.
While 3D printing excels at rapid production, 3D printing jobs using techniques such as Multi Jet Fusion (MJF) and Fused Deposition Modeling (FDM) can take hours to complete, depending on the geometry and size of the part. If the part is a simple geometry with limited machining times, CNC machining may be a faster operation. CNC machining can require more operations than 3D printing, and machinists must manually reposition fixtures or parts during the build process, extending machining times.
In addition, 3D printing offers the freedom to design complex master patterns, including holes, organic shapes, and channels that cannot be achieved with CNC machining. It also opens the door to part consolidation, where multiple components can be combined into a single part design to reduce tooling count. CNC machining patterns can achieve complex geometries, but the more complex the design, the more it relies on hand fabrication and post-processing.
In conclusion
Subtractive and additive manufacturing are suitable for different purposes, but at the end of the day, there is no use in using 3D printing to replace the work of a CNC machine. For example, 3D machines require fairly specific metal types to function optimally, leading to less versatility and leeway in terms of materials that can be used for metal-based projects. They also don’t offer the same efficiency when it comes to mass production, they have to wait for each layer of material to dry causing a time delay, CNC machines can do multiple functions at the same time. Therefore, if you are looking for the best value for money while maintaining the integrity, detail, quantity, quality, speed and variety of material possibilities, CNC machining is the best option.
