Manufacturers are always seeking the best ways of optimizing production, reducing costs and improving the outcomes of their parts and products. Among the various methods of manufacturing, two are highly prominent: additive and subtractive manufacturing. Both have risen as ways of expediting prototyping but over time they have been used more and more in end-part manufacturing. How do these manufacturing processes work? What’s the difference? And which one is the better choice for your business’s manufacturing needs? Here’s what you should know.
In additive manufacturing, material is added layer by layer to form a three-dimensional solid object using computers and 3D printers. Common materials used include powder and liquid, and can produce parts in plastics, metals and more. Additive manufacturing is well suited to producing customizable products, specialized parts, and highly complex or intricate parts.
Here are some popular types of additive technologies:
In this process, a thermoplastic material is heated to its melting point and extruded from a nozzle to create the layers of the desired three-dimensional object on the build plate. Fused Deposition Modeling is an example of material extrusion and is the most commonly used process in 3D printing.
Material jetting is an inkjet printing method in which a liquid photoreactive material is deposited onto the build plate and is then hardened with UV light.
Binder jetting alternates the deposit of two materials, a powder and a binder, layer by layer to create the solid structure. The object is then removed from unbound powder when it has finished printing.
Sheet lamination stacks and laminates sheets of material like plastic, paper or metal layer by layer. This process is fast and low-cost, making it well suited for low fidelity prototypes.
This process uses a vat of liquid photopolymer resin that is selectively cured by UV light. Stereolithography (SLA) uses this technique and was the first patented 3D printing technology.
Powder Bed Fusion
Powder bed fusion uses a laser or electron beam to fuse powder material together and is typically used for plastic or metal parts. This process includes Electron Beam Melting, Selective Heat Sintering and Multi Jet Fusion technologies.
Directed Energy Deposition
Directed Energy Deposition uses a nozzle mounted on a multi-axis arm to melt and deposit material. This process typically uses metals in powders or wire.
In subtractive manufacturing, material is gradually removed from a solid block to form a three-dimensional object with the help of computers and robotics. Material can be cut, drilled, bored, milled, chipped, or melted away depending on the desired results and the technology being used. Subtractive manufacturing is typically used to produce sturdy, high volume parts and products.
Here are some popular types of subtractive technologies:
Computer Numerical Control (CNC) Machining
CNC (computer numerical control) machining is a process in which tasks are pre-programmed into computer software and then delivered to factory tools and machines to cut away from the material block in a precise, three dimensional way to deliver the desired object. The tasks delivered to the machines can be given manually, but lately CNC has mostly taken on that job.
Electrical Discharge Machining (EDM)
EDM is a manufacturing method in which thermal energy is used to remove material. An electrode emits an electrical discharge that erodes conductive material and is typically used with metals like titanium or steel.
This method uses the output of a high powered laser to vaporize, melt, burn or slice materials until they reach their desired shape. CNC codes determine the movement of the laser beam to create continuous cuts and define the object being produced.
Water Jet Cutting
Water Jet Cutting uses a high-powered jet of water to cut material and can either function with water alone (pure water jet) to cut softer materials that cannot withstand higher temperatures, like rubber or wood, or it can also be combined with an abrasive substance (abrasive jet) to cut harder materials like metals or stone.
Key Differences Between Additive and Subtractive Manufacturing
Subtractive and additive manufacturing both present their share of benefits depending on the project at hand. Subtractive manufacturing has been prominent over the years when it comes to manufacturing high quality prototypes or mass-produced parts, especially in metal. Additive manufacturing has been evolving quickly, however, and is becoming more commonly used than ever, especially when it comes to on-demand manufacturing and mass customization, which it is much more suited for. It is also the optimal choice for plastic parts and prototypes.
Some key differences between the two include:
Weight and Density Control
In subtractive manufacturing, the final object will have the same density as the original solid block of raw material it started from, which works well for creating sturdy parts. With additive manufacturing, however, manufacturers have the ability to create hollowed parts and control the weight of the desired object.
Additive manufacturing is known for its ability to generate intricate parts that have pushed the limits of design possibility. Subtractive manufacturing is able to produce complex shapes as well but does not offer nearly the same level of design freedom as additive manufacturing.
Subtractive manufacturing relies on the removal of bulk material to achieve a desired object, however, this can yield a substantial amount of waste as unusable chips, dust, scraps still remain after the object is complete. Additive manufacturing cuts down on that type of waste considerably, as it typically only uses as much material as is needed.
Subtractive manufacturing is better suited for making a high volume amount of the same part or product, while additive manufacturing is best suited to making one of a kind or small-run parts that can be customized to suit customers or specific situations.
Costs and Space
Previously, subtractive manufacturing was overall a less expensive process, but additive manufacturing prices have been dropping as it is further developed and made more accessible. Both methods require some specialized equipment and training to use. CNC machining typically required a workshop or dedicated space to use the necessary equipment, where 3D printers range in sizes and prices from compact desktop printers to large, industrial ones. By utilizing a 3D printing service like Shapeways, the equipment start-up costs and training are no longer barriers to entry in using additive manufacturing.
Understanding the fundamental differences between additive and subtractive manufacturing processes will allow you to select the manufacturing service that is better suited for your unique product.
As the industry leader in additive manufacturing, our 3D printing experts are here to help you with your manufacturing needs.