Comparing CNC Machining and FFF 3D Printing: 5 Key Differences

CNC machining and FFF (Fused Filament Fabrication) 3D printing are both efficient production technologies in the manufacturing industry. However, from a technical standpoint, there are fundamental differences between CNC and FFF 3D printing. The former consists of subtractive manufacturing, while the latter is an example of additive manufacturing. For instance, if we were to manufacture a gear using CNC machining and FFF 3D printing technology respectively, the CNC machining will slowly cut the gear shape from a large piece of material like a carving machine, and then detail it to form the final part. In contrast, FFF 3D printing is similar to building blocks, stacking materials layer by layer to get the final product.

Due to the differences in their fundamental principles, CNC machining and FFF 3D printing exhibit varying degrees of divergence in material, operational costs, production speed, and more. These differences shape the unique characteristics and advantages of both CNC and 3D printing. When applied to production, these technological differences ultimately translate into variations in cost, quality, production time, and return on investment across multiple aspects. These factors are precisely what determine their suitability for different application scenarios.

5 Key Differences Between 3D Printing and CNC Machining

1) Difference between CNC machining and FFF 3D printing and forming principle

CNC machining is the process of performing machining operations such as drilling, milling, and turning on a workpiece, resulting in precisely crafted components. One of the most distinctive features of CNC machining is its high precision. It is capable of achieving tolerances as small as 0.004mm, resulting in the manufacture of high-specification parts. CNC machine tools typically feature a rotating tool carousel for swift tool changes, capable of simultaneously holding over 20 tools at maximum capacity. Additionally, CNC exhibits high consistency, ensuring the quality of product batches.

CNC machining also has certain limitations. During the CNC machining process, the tools are subject to physical constraints imposed by the required geometric shapes. For instance, parts with deep cavities may require long-axis tools for cutting, but longer tools may induce vibrations, thereby affecting precision. Additionally, in the hollow machining of solid bodies, CNC inevitably leaves marks on the object’s surface. For example, achieving hollow processing for a solid sphere is challenging with CNC machining.

As a result, there are actually some limitations to the freedom of CNC in structural shaping. In addition, when designing parts, engineers also need to consider the points of tool contact, installation positions, blind spots, etc. This also implies that CNC has certain constraints in terms of shaping structures.

There is a wide range of tools available for CNC machining. Before machining, engineers need to select materials according to the work requirements of the parts. Then, engineers also need to choose the machining process and cutting tools according to the structure of the part, the material and other production requirements. The CNC machining process is quite complicated compared to high-speed FFF 3D printing. FFF 3D printing has less prep work and simply requires the selection of an appropriate nozzle and material based on part size and manufacturing requirements.

FFF 3D printing, on the other hand, is an additive manufacturing technology that heats thermoplastic materials and extrudes them through a nozzle following the path defined by slicing software, layer by layer, to create the final component. The entire 3D printing process is analogous to building blocks layer by layer. Because it builds up from scratch, 3D printing is not constrained by manufacturing processes.

In other words, when designing and producing parts with complex geometric structures, FFF high-speed 3D printing offers greater flexibility. CNC machining is typically more suitable for producing parts with high precision and surface quality requirements, and is more cost-effective for large-scale production.

2) Difference in material application of CNC machining vs. FFF 3D printing

CNC machining is mainly applied to materials, both metallic and non-metallic, that can be rapidly formed, and have good hardness and deformation resistance characteristics. Metallic materials such as aluminium, steel, copper and alloys are widely used in various industrial fields. Non-metallic materials such as plastics and wood can also be CNC machined to create parts and models. Multi-material suitability also allows CNC to have a wide range of applications in the machining field, thus ensuring high precision and quality for different types of parts.

FFF 3D printing technology is flexible in terms of material application, and it is compatible with many types of thermoplastic materials. Common FFF printing materials include PLA, ABS, ASA, PETG, which are more common and relatively cost-effective in the market. FFF technology also supports composite materials, like carbon fiber-reinforced materials, which are used to enhance the strength and lightweight nature of parts. Moreover, some high temperature and chemical resistant materials are available for specific applications under challenging conditions.

With the constant development and advancement of material science in recent years, an increasing number of new materials have begun to be added to the material reserve of FFF 3D printing. For example, materials such as silicone materials, biocomposites, biodegradable materials, etc., have greatly increased the range of applications that can be achieved with FFF 3D printing, surpassing through people’s expectations for the application of normal filaments. FFF 3D printing materials also have a rich color diversity to create coloured parts.

Compared to CNC machining, which is mainly used for mechanical applications, high-speed FFF 3D printing has a wider range of material compatibility, which also broadens its commercial boundaries. FFF 3D printing enables more cost-effective material selection options than CNC machining when dealing with some applications. For example, in the production of some jigs and fixtures, PLA, ABS, ASA, PETG, etc. can be used to meet the actual work requirements of the application at a relatively low cost. Also, these jigs and fixtures are lighter and softer than metal fixtures, which prevents scratches on the surface of the workpiece to a large extent.

In addition, when dealing with the production of some high-performance lightweight parts, such as aerospace parts and automotive parts, polymer composites supported by FFF 3D printing, such as carbon fiber-reinforced filaments and glass fiber-reinforced filaments, are easily capable of doing the job. However, these can be a challenge for CNC machining. Also, FFF 3D printing can achieve flexible manufacturing. Materials such as TPU or silicone are a very good choice of materials for footwear, elastic restraint parts and protective equipment, something which CNC machining would have difficulty realizing.

It is worth mentioning that some biodegradable materials such as PLA in FFF 3D printing materials can be used to make medical implants such as bone repair scaffolds, as well as food packaging or disposable medical tools. There are many more such material application cases in FFF 3D printing, which make up for the application limitations when compared to CNC in some fields, and at the same time provide more cost-effective material selection options.

3) Comparison of CNC machining and FFF 3D printing production process and lead time

The entire CNC machining process is relatively complex, covering multiple steps such as parts design, tooling and fixturing, CAM programming, machine commissioning, machining, and verification. Depending on the complexity of the part, programming can take from a few hours to a few days. Due to the number of preparation procedures for CNC machining, the commissioning of a machine usually requires more than 10 steps, and depending on the complexity, the entire machining cycle can take from a few hours to several days. CNC machining of complex workpieces is usually even more time-consuming.

In addition, CNC machining has a long iterative cycle. If a product fails the validation process, it needs to go back to the design stage and go through production again, which also increases the potential risk of delayed deliveries and increased costs.

In contrast, high-speed FFF 3D printing technology eliminates the need for a complex and time-consuming programming process. The digital model can be sliced by the slicing software and then be printed directly. In addition, compared to CNC machines, 3D printers also have a simpler and less time-consuming process of adjusting the machine before printing. In terms of the entire production process, FFF 3D printing can usually achieve rapid part production.

By comparing the data in the graph above, we are able to more intuitively understand the difference in production time between traditional CNC machining and high-speed FFF 3D printing for the same part, which directly affects the production cost.

Typical FFF 3D printers have a print speed of 50 mm/s-150 mm/s. Therefore, even with the production flexibility compared to CNC machining, the actual processing speed is not very fast. However, it is worth mentioning that Raise3D offers Hyper FFF^® technology, which greatly improves the speed of FFF 3D printing. Hyper FFF^® is a system engineered for efficiency and performance, which will increase the yield rate of FFF printing without any loss of printed part quality. The core of the Hyper FFF^® technology is the active vibration cancellation algorithm. The algorithm will calculate an optimized acceleration pattern and absorb the excessive amount of vibration whenever the printer head makes any high-speed change in direction. In addition, Hyper FFF® ensures the accuracy, surface quality and stability of Raise3D FFF high-speed 3D printing through the optimization of hardware such as logic controllers, metal frames and motion controllers.

Raise3D Pro2 Series High Speed Upgrade achieves L1 print speed, 100mm/s-200mm/s, with over 200% speed increase and 100% quality improvement. Raise3D Pro3 Series High Speed Upgrade Kit achieves L2 print speed, 200mm/s-350mm/s, with over 300% speed increase and 100% quality improvement compared to the original printer model. The Raise3D Pro3 series high-speed upgrade kit achieves L2 print speeds, 200mm/s-350mm/s, with over 300% speed improvement and 100% quality improvement over the original printer models.

Learn more about Raise3D Hyper FFF^® technology：

https://www.raise3d.com/hyper-fff/

Moreover, for high-speed FFF 3D printing batch production, the overall production speed is also related to 3D printing task management. Efficient multi-task management capabilities can improve production efficiency to a certain extent, and reduce the pressure of personnel management. For batch production print jobs, Raise3D offers RaiseCloud, a web-based 3D printing platform that remotely controls, monitors and reports your team’s entire print production progress at a glance. Users can also modify parameters remotely to increase production flexibility.

Learn more about Raise3D RaiseCloud:

https://cloud.raise3d.com/raise3d.html

Furthermore, Raise3D provides a series of high-speed materials for Hyper FFF printing technology, including Hyper Speed and Hyper Core series. The Hyper Speed series, developed for high-speed FFF printing, features high flowability, optimized molecular weight, easy printability, and excellent surface finish, as well as excellent interlayer bonding, and is represented by the Hyper Speed PLA and Hyper Speed ABS filaments. The Hyper Core series features tailored fiber distribution to provide a smooth surface finish, excellent interlayer bonding and less nozzle wear, and is represented by Hyper Core ABS CF15, Hyper Core PPA CF25 and Hyper Core PPA GF25.

Learn more about Raise3D Hyper Speed Filaments:

https://www.raise3d.com/filaments/raise3d-high-speed-filament/

4) Comparison of CNC Machining and FFF 3D Printing Material Wastage

CNC machining, as a subtractive manufacturing method, involves significant material waste. CNC machining typically requires precise shaping of the desired form from a solid raw material through processes such as cutting and carving. This process can generate a notable amount of waste, especially in complex machining tasks where multiple tool changes and angles might be needed, contributing to even more waste.

In contrast, FFF (Fused Filament Fabrication) 3D printing technology exhibits relatively lower material waste. As mentioned earlier, FFF prints by layering materials, using only the amount of material required for constructing the part, minimizing excess waste. Even in cases where support material is used during printing, the additional material consumption is minimal. Therefore, this efficient manufacturing approach is well-suited for small-batch production and rapid prototyping. From a sustainability perspective, FFF 3D printing is also a more environmentally-friendly method.

5) Cost comparison between CNC machining and FFF 3D printing

CNC machining usually has an advantage over FFF 3D printing in terms of part accuracy. However, in general-purpose areas, both CNC machining and FFF 3D printing have superior manufacturing capabilities, and FFF 3D has the advantage of higher production cost-effectiveness.

In terms of operational steps, the CNC machining process is obviously more complex, so there are more greater expenses involved:

• Initial investment, depreciation and maintenance of CNC machining equipment
• Purchase and maintenance costs of cutting tools
• Customized production of work holding jigs and fixtures
• Labor hours and training costs for technicians such as operators, programmers, etc.
• Material costs
• Energy costs

Engineers need to prepare data and programming before CNC machining. They must also consider tool selection, machining blind spots, spindle speeds, cutting paths, fixture clamping, and more. That complexity of the entire CNC machining process requires a high level of skill from the technicians. For mass production, both the labor and equipment costs will increase significantly. In addition, the investment cost of the CNC equipment and the annual depreciation cost is also a major expense.

The following depreciation cost information can simply be used as a reference.

The following is a reference for cost data for 5-axis CNC cutting machines:

The following is a reference for the cost data for the Raise3D FFF 3D printers.

Prices of some CNC tools

In contrast, FFF 3D printing technology has the advantage of controlling operating costs. In addition to lower cost raw materials for fabrication, FFF 3D printing also eliminates the need for expensive cutting tools. Additionally, the machining of parts requires supporting jigs and fixtures, which range in price from a few dollars to several hundred dollars, and can be even more expensive when it comes to customized fixtures of high standards and complexity. Therefore, FFF 3D printing is more economical at the level of total production equipment investment and maintenance costs.

With a set of batch production case data, we can better understand the gap between CNC and 3D printing in terms of cost-effectiveness:

As an example, for the small batch production of a specific battery cell cleaning tray (0-1000 sets), each set of trays is formed by a combination of 7 parts. It takes a total of 21 hours to produce these 7 parts using a Raise3D high-speed 3D printer.

The cost of FFF 3D printing production mainly consists of the average equipment depreciation cost of 3D printers, material costs, average energy consumption and consumable parts, and labor costs. Among them, the labor amortization cost decreases as the number of printed parts increases. As seen in the above example, when the 10th set is produced, the unit processing cost savings can be nearly 43%. With further increase in quantities, this ratio tends to be nearly 48%. By comparing the production cost, high-speed FFF 3D printing is more cost-effective compared to CNC machining when producing small batches.

Besides, another set of data can be used to understand the cost difference between producing small batches of different jigs and fixtures through in-house 3D printing and outsourcing. By manufacturing a batch of fixtures in the same material with the Raise3D printer, the production cost is only 0.3%-6.8% of CNC, which is a significant cost reduction.

Conclusion

FFF 3D printing and CNC machining are two distinct manufacturing methods. While they have differences in technical characteristics and advantages, their relationship is more about complementing each other’s strengths rather than a purely competitive or substitutive relationship. Currently, 3D printing has demonstrated high economic benefits in fields such as prototyping, small-batch production, and spare part manufacturing. This rapid manufacturing technology reduces manufacturing cycles and costs while offering greater innovation possibilities. CNC machining provides high accuracy and surface quality, suitable for workpieces that require precision, complexity and high strength, and it remains one of the dominant methods of production machining.

Looking ahead, with the continuous development of 3D printing technology and its integration with CNC technology, manufacturing processes will be further optimized. We can anticipate that, in some areas, 3D printing might gradually become a mainstream of small batch manufacturing methods. In the future, FFF 3D printing is also expected to be combined with CNC machining to create a more complete manufacturing ecosystem.