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Settling the Debate: CNC Machining vs. 3D Printing

 CNC routing is essentially the reverse of 3D printing. Instead of using a computer to control the armature and print head that layers substance in three dimensions, CNC routing utilizes a drilling tool to carve materials. This is basically the difference between making a sculpture out of clay and carving it from marble, only in this case, there’s a robot doing it instead of a human.

Settling the Debate: CNC Machining VS. 3D Printing

CNC milling technology has existed ever since MIT introduced it in the 1950s. CNC routing is essentially the reverse of 3D printing. Instead of using a computer to control the armature and print head that layers substance in three dimensions, CNC routing utilizes a drilling tool to carve materials. This is basically the difference between making a sculpture out of clay and carving it from marble, only in this case, there’s a robot doing it instead of a human.

Three-dimensional printing has gone mainstream, challenging the way people think about printers. As consumers become familiar with 3D printing, they often struggle with the complexity of the new technology. Similarly, business customers have become aware of 3D printing and are now looking for the ways to make the technology work for them. Although 3D printing might still seem novel, new printers continue to emerge as an alternative to the established CNC routers in production environments.

This article aims to help the readers assess the utility of 3D printers when compared to CNC machines, with regard to precision, materials, cost, quality, efficiency, and speed. 

Image courtesy of wikipedia.org

Image courtesy of wikipedia.org

Different Processes

Although computer-aided design software works with CNC routers and 3D printers, the two technologies use various methods to create outputs. In fact, CNC routers use a method that works opposite of the way 3D printers work. CNC machines start with a block of material and cut away at it until nothing remains except the intended product. On the other hand, 3D printers start from nothing and add layers of a specialized material to form a mass that assumes the shape of the product design. This additive process makes 3D printers flexible enough to create a variety of outputs, limited only by the capability of the printer. 

Albeit the subtractive process of CNC technology often produces faster results than the additive process of 3D printers, both approaches to production have advantages that make each type of machine well-suited to achieve differing objectives. 

Image courtesy of makerbot.creativetools.se

Image courtesy of makerbot.creativetools.se

Different Purposes

CNC milling and 3D printing have characteristics that make them suitable for particular uses. A CNC router can efficiently produce considerable quantities of large, heavy, precision-crafted products to be used for commercial and industrial equipment, machines, and engines. CNC machines can use a variety of materials for production and create large quantities of a given product, although they can also produce small batches of products, usually at a higher unit cost. 

The flexibility of a 3D printer enables it to quickly change between various jobs. However, since the cost per unit of a given output is always the same, regardless of quantity, such printers are uneconomical for large production jobs. The adaptability of 3D printing, however, makes it useful for creating unique, personalized designs for particular customers. 3D printing has become a favorite tool for artists and other creative professionals who thrive on creating one-of-a-kind products. New technologies have harnessed the flexibility of 3D printers for use in medical and dental settings, creating customized items that fit particular patients. 

Image courtesy of wikimedia.org

Image courtesy of wikimedia.org

Size

CNC routers have the capability of scaling between large and small outputs. The scale of the output produced by a CNC router depends on the capabilities of the machine and the raw material used in production. On the other hand, 3D printers use an additive, layering process that makes them ill-suited for the production of large items. Existing 3D technology can scale from creating small, customized items to producing larger objects similar in size to a small refrigerator.

Despite the fact that 3D printers will most likely evolve to become capable of producing bigger objects, they probably will not catch up to the extensive capabilities offered by CNC machines. Furthermore, the time required to print large objects also limits the scalability and feasibility of 3D printing technology.

Image courtesy of pixabay

Image courtesy of pixabay

Materials

At this time, heavy-duty outputs made from high-density metals with high tensile strength come from CNC routers. CNC outputs include precision parts used in engines, airplanes, production machinery, and other high-intensity environments. Moreover, CNC routers can also make outputs from wood, wax, plastic, and almost any other material.

Most 3D printers use additive processes to create products from specialized plastics, resins, metals, and other materials. As a result of the unique materials used for the printing process, 3D parts usually do not have the necessary strength for use in demanding settings including airplanes, vehicles, and production machinery. Instead, the materials used to print 3D objects work well for creating models used for prototypes as well as consumer-grade products for home and personal use. 

New 3D technology for use in the production of medical and dental products use unique FDA-approved materials, and the new metal 3D printers underscore the evolving nature of 3D printing technology. While no 3D printer can now create the same quality of output as a CNC router, the future holds almost unlimited possibilities.

Image courtesy of pixabay

Image courtesy of pixabay

Precision

CNC machining also provides superior surface quality when compared to the best outputs 3D printers can produce. CNC-produced parts can go straight to their destination whereas the output from 3D printers usually requires separate steps for finishing a task. This makes the 3D printing process less efficient than the CNC process.

3D printers lack the precision necessary for mission-critical applications. Even with Selective Laser Melting (SLM) technology that prints 3D outputs in metal, 3D printing cannot replicate the accuracy of CNC machines. To illustrate, CNC milling can provide mechanical accuracy of one micrometer on every axis, a level of precision impossible with 3D equipment. 

Image courtesy of wikimedia.org

Image courtesy of wikimedia.org

Speed

CNC machines start with milling a block of material so as to meet design specifications. When speed becomes a factor, CNC machines can trade accuracy for speed, thus giving operators control over production time. 

 As a general rule, using the additive processes of 3D printing to make something from nothing takes longer than using the subtractive process of removing material from a block of the existing material. Conventional 3D printing uses a slow process to create layers of material that gradually form the desired output. 

Like a paper printer, the 3D printer itself determines print speed – to increase the rate of production, a faster printer is required. Even at its best, 3D printers cannot keep pace with CNC machines. Even after a 3D printer finishes, the output requires further attention before use. Specifically, the post-production process requires manual removal of complex supports before washing, polishing, and curing the product before it becomes useful.

The variety of available 3D printers and materials makes production-time comparisons with CNC mills difficult. For the most part, jobs take longer to finish when there is a larger volume of material to solidify. For CNC products, production time depends on the machined surface area and the amount of material removed. Generally, CNC production offers advantages in speed over 3D print jobs. 

Image courtesy of wikipedia.org

Image courtesy of wikipedia.org

Price

The differences between CNC milling and 3D printing technologies make comparisons on a per-part basis difficult. The definition of a typical unit varies between customers, materials, and jobs. Although price considerations may factor in the decision between the use of a CNC router or a 3D printer, comparisons often come in general terms. 

When using CNC machines to create a certain part, small quantities usually come with a higher unit cost, but large batches become increasingly economical. This makes CNC an ideal choice for mass production. With 3D printing, every unit of output costs the same, regardless of the batch size. When producing small quantities of an item, the equal cost of every unit produced represents an advantage, but when producing large amounts of an item, the uniform cost per unit can become a problem.

With CNC machines, the unit cost of a product can increase according to the complexity and precision of the output. The higher cost of complicated CNC outputs often stems from the larger number of tool paths required, the smaller cutters used, and the amount of time needed to complete those jobs. 3D print jobs, however, cost the same, regardless of the complexity of the units produced. 

Image courtesy of matthew venn via flickr

Image courtesy of matthew venn via flickr

Advantages

An advantage of one technology may often be the disadvantage of the other. In this section, a list of main advantages for each of the two technologies will be presented.

CNC machining:

1. A broad selection of materials to use for production.
2. Freedom to choose the resolution of production in exchange for speed or cost benefits.
3. Superior quality surfaces and high precision.
4. Price constant regardless of the product size and volume.
5. Low-cost machinery and supplies. 

3D printing:

1. Easy to use: easy to prepare for an operation.
2. Part complexity does not affect the price of the part.
3. The limitless capacity to create products with intricate designs.
4. Price constant regardless of the batch size.
5. Flexibility to quickly change production jobs. 


Conclusion

To a certain degree, CNC technologies and 3D Printing overlap in capability, but they each have strengths that make them suitable for specialized applications. CNC mills will usually work best for projects that require sophisticated, high-precision products made from readily available materials. The characteristics of 3D printers make them ideal for the creation of prototypes, visual justifications, and custom-designed products. All things considered, the world has plenty of room for both 3D printers and CNC machines.