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CNC vs 3D Printing Technology: Which One to Choose for Prototyping Production

cnc vs 3d printing

Published:  August 19, 2022         Reading Time:  About 3 minutes

When it comes to manufacturing technologies, nothing beats the fame and recognition of CNC machining and 3D printing. Both technologies make the job easier for manufacturers, allow more complicated designs, and maximize the overall benefit at little to no additional cost.

However, the question remains which one is the better alternative? CNC vs 3D printing is an old debate with no clear answer.

Both technologies have their merits, but the right choice for you depends on a plethora of factors. This text will take a brief look at CNC machining vs 3D printing and discuss some of the main factors or considerations that determine the right kind of technology for you.

Subtractive and Additive Manufacturing

cnc vs 3d printing

Before delving further into the debate between CNC and 3D printing, it’s important to have a basic understanding of both technologies and the manufacturing process.

CNC and 3D printing are two popular technologies used in manufacturing. CNC stands for Computer Numerical Control, and it involves starting with a block of material and using a computer-controlled machine to remove the material until the desired shape is achieved. This is known as subtractive manufacturing.

In contrast, 3D printing, also known as additive manufacturing, involves building up a part layer by layer using a computer-controlled printer. This technology adds material rather than removing it, resulting in less material waste.

Both technologies have their advantages and disadvantages, and choosing the right technology for a particular application depends on factors such as the complexity of the part, the required precision, and the material properties. For more different differences between additive and subtractive manufacturing. The next sections will take a brief look at their fundamentals.

What Is 3D Printing

3D printing is a famous and flexible manufacturing technique with numerous advantages and industrial applications. The term is interchangeable with additive manufacturing, which is an umbrella term for all techniques. Additive manufacturing units fabricate any section in layers which allows better design flexibility and versatility. Moreover, 3D printing is also a faster and more recommended method for rapid prototyping as its faster and more cost-effective for smaller batches.

Another important thing about 3D printing is it has numerous types. This means more freedom to choose between the material, technique, speed, finish, printing cost, and other technical factors to get the exact results you want for a project.

3d printing

Modern industry uses numerous methods to obtain favorable results from 3D printing technology. However, the following 3D printing techniques are the most common across the industry:

  • Binder Jetting
  • Material Jetting
  • Material Extrusion
  • Vat Polymerization
  • Powder Bed Fusion
  • Direct Energy Deposition
  • Sheet Lamination

There is a common misconception about 3D printing that it’s only limited to thermoplastics and other similar compounds. However, the reality is quite different now. Today, 3D printing metals, bio-compounds, ceramics, and other materials are also possible, which adds to the overall versatility of the technology.

The misconception related to the use of thermoplastics only comes from the fact it is still the most commonly used material for 3D printing applications. One of the most important uses of application is rapid prototyping of products to test out the design liability. Thermoplastics are a perfect choice for that as they cure faster and are relatively cheap.

There are still some limitations of the 3D printing technology related to volume production because of associated costs and time requirements. However, the technology is advancing at a rapid pace and has a lot of potential for industrial applications.

What Is  CNC Machining

CNC machining is an advanced process that replaces human input from machining. A CNC machine uses a computer to gauge the required movement of the machine’s cutting tool and give the most accurate results. For CNC, the process starts with the CAD model which the computer uses to translate into either G-codes or M-codes. These codes are specialized languages that the CNC machine understands to create the shape you desire.

cnc machining

Apart from the excellent accuracy, one thing that makes CNC machining so favorable for the industry is repeatability. If you compare it to the traditional machining approach, it depends on the overall skills of the operator. Moreover, the results would vary greatly because it’s impossible for the operator to perform in the same way throughout the day. CNC machining doesn’t have that problem as computers are in full control of the system and require little to no human input.

With CNC machines, you can experience a plethora of benefits starting from increased efficiency to increased production speed, and lower costs at minimal risks. This increases the technology’s feasibility for any business and is one of the most important reasons behind its overall global acceptance.

Key Similarities Between 3D Printing and CNC Machining

Naturally, both 3D printing and CNC machining are entirely different technologies with separate applications and focuses. However, there is one huge similarity between them as well. Both technologies often involve using CAD models. While 3D printers use the CAD model directly to build the part layer by layer, CNC machines use it as a reference to generate G/M codes, which guide the cutting tool to create the final product. In some cases, designs may transition from a 3D printer to a CNC machine for final production.

CNC vs 3D Printing: 10 Considerations Before You Choose Between the Two

One of the most important decisions any product designer or engineer makes before the start of production is when selecting the manufacturing method for the product. It’s imperative to find the perfect balance between cost, speed, and accuracy for the best performance and maximum profit. If the product leans toward one parameter at the expense of other, the final result would be far from what you need. That’s why the design phase takes so many resources as you’ll need to balance both the technical factors and the overall costs.

When evaluating 3D printers vs CNC machines, there are a lot of considerations in addition to the constraints of speed, time, and cost. Here are some of the most important considerations for any business deciding between the two technologies.

Selecting the Ideal Material

cnc machining material

The first consideration is perhaps the most important one, as the material is still the biggest technological constraint for 3D printing. It’s possible today to 3D print different materials ranging from metals to ceramics. However, there are still many limitations when it comes to the overall mechanical properties of your part.

CNC Machining Materials

CNC machining offers a wide range of material options, including metals, plastics, and composites. This versatility makes CNC machining suitable for various applications, from aerospace components requiring high strength and temperature resistance to consumer products demanding specific aesthetic qualities.

Some common materials used in CNC machining include:

Metals: Aluminum, stainless steel, brass, titanium, copper, and various alloys are frequently machined to create durable, high-performance parts.

Plastics: ABS, Nylon, Polycarbonate, PEEK, and other engineering plastics are often machined for their lightweight, corrosion-resistant properties, and ease of machining.

Composites: Carbon fiber reinforced polymers (CFRP) and other composite materials can be machined to produce lightweight, high-strength components for aerospace, automotive, and other demanding applications.

3D Printing Materials

3D printing materials have expanded significantly in recent years, but the selection is still more limited compared to CNC machining. The availability of materials also depends on the specific 3D printing process being used.

Common 3D printing materials include:

Thermoplastics: ABS, PLA, Nylon, PETG, and PEEK are widely used for their affordability, ease of printing, and range of properties.

Thermosets: Epoxy resins, polyurethane, and silicone are often used in Stereolithography (SLA) and Digital Light Processing (DLP) 3D printing for their high resolution and smooth surface finish.

Metals: Aluminum, stainless steel, titanium, Inconel, and other metal alloys can be 3D printed using processes like Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS) for producing high-strength, functional metal parts.

Below is a comparison chart highlighting some key differences in material options between CNC machining and 3D printing:

FeatureCNC Machining3D Printing
Material VarietyWide range of metals, plastics, and compositesMore limited, but expanding rapidly
Material PropertiesExcellent mechanical properties, isotropic behaviorCan vary depending on the printing process, anisotropic behavior in some cases
Metal OptionsWide range of metal alloys availableLimited to specific alloys compatible with the printing process
High-Performance MaterialsSuitable for machining high-temperature alloys and superalloysLimited availability of high-performance materials for 3D printing
CostMaterial costs vary widely based on type and gradeSome 3D printing materials, especially for metal printing, can be expensive

For instance, 3D printed metal parts don’t come with that much fatigue strength and may also need a lot of heat treatment before they are ready to use. This can cause the overall cost to skyrocket and make the process unfeasible for your business. CNC machining would be a better choice in this regard as it can quickly process metal and doesn’t require any heat treatment.

Contrary to that scenario, there are many materials where 3D printing would be a better choice as well. In the end, it all comes down to the specifics of the project, and you have to decide while considering all the related factors.

What Is Your Expected Production Volume

This is another important consideration that determines the right manufacturing process for you. The manufacturing industry has relied on the economies of scale concept for the longest time. This means that the more parts you produce, the more cost-effective your production will be. Today, both CNCs and 3D printing play a part in volume production.

On one side, CNC machines automatically create the required part with minimal human input while working 24/7. On the other hand, 3D printing is a common choice for creating prototypes and even complex molds for further volume production using methods like the casting process. However, if volume production is the deciding factor, most go with CNC machining because of the cost overheads and the fact that there is no other process involved.

What Is Your Part Size

Another essential consideration while deciding between CNC vs 3D printing is the size of the part. Generally, CNC machines can handle bigger parts because of their size. 3D printers have so many associated costs that make going beyond a certain size unfeasible.

CNC Machined Part Size

CNC machines can typically handle a wide range of part sizes, from small, intricate components to large, complex structures. The maximum part size that can be machined depends on the specific CNC machine’s work envelope, which is the three-dimensional space within which the machine can operate.

3D Printed Part Size

3D printers have size limitations based on the build volume of the printer. Most desktop 3D printers have a build volume of less than 1 cubic foot, while industrial 3D printers can have larger build volumes, but they are still generally smaller than CNC machines.

The table below compares the part sizes and tolerances for CNC machining and several 3D printing technologies:

TechnologyMinimum Part Size (mm)Maximum Part Size (mm)Typical Tolerance (mm)Typical Applications
CNC Milling5 x 5 x 5 (RapidDirect)4000 x 1500 x 600 (RapidDirect)±0.0076 (Standard), ±0.0025 (Precision)Large enclosures, automotive components, aerospace parts
CNC Turning2 x 2 (RapidDirect)Diameter: 200, Length: 500 (RapidDirect)±0.0051 (Standard), ±0.0013 (Precision)Shafts, bushings, gears, cylindrical components
SLS0.7 – 1.0 (Wall Thickness)300 x 300 x 300± 0.300Prototypes, functional parts with complex geometries, low-volume production
FDM (Industrial)0.8 – 1.0 (Wall Thickness)900 x 600 x 900± 0.200Prototypes, tooling, jigs and fixtures, concept models
SLM/DMLS0.40 (Wall Thickness)230 x 150 x 150± 0.100High-performance metal parts, aerospace components, medical implants
Binder Jetting2.0 (Wall Thickness)380 x 355 x 735± 0.200Sand casting molds, prototypes, large, complex parts with intricate details

In this case, the best approach is to consider the specifics of the project. However, the general principle that CNC is a better choice for larger parts holds true in most cases.

How Complex Is Your Design?

This is an area where 3D printers shine. Since they develop directly from the CAD model, there are almost no designs that 3D printers can’t handle. Machining, whether traditional or CNC design, requires a lot of input from experts to ensure that there are no hindrances to the cutting tool. Thereby making a lot of complex designs either impractical or impossible.

complex shapes made with 3d printing

On the other hand, 3D printing is not only free from all these restrictions. It can also go a step above and handle hollow designs and other features that are not possible for other manufacturing techniques.

With Dimensional Accuracy in Mind

The dimensional accuracy you need will also have an effect on the right technique for you. Both CNC machines and 3d printers are quite accurate and deliver consistent results. However, CNC machines still depend on the initial input from the operator and the G/M codes. 3D printers don’t have that issue and give you consistent results. Their difference is, however, quite small and negligible for most common applications. Therefore, CNC and 3D printing stand toe-to-toe in this regard.

CNC Machining Accuracy

CNC machining is known for its high dimensional accuracy and repeatability. Advanced CNC machines with multi-axis capabilities and sophisticated tooling can achieve tight tolerances, often in the range of +/- 0.0025 inches or better. Factors that influence CNC machining accuracy include:

Machine rigidity and precision: The stiffness of the machine structure and the accuracy of its motion control systems directly impact the accuracy of the machined parts.

Tooling quality and wear: Sharp, high-quality cutting tools and proper tool wear management are essential for maintaining dimensional accuracy.

Material properties: The machinability of the material, including its hardness, chip formation characteristics, and tendency to warp or distort, can affect accuracy.

Fixturing and workholding: Secure and accurate fixturing of the workpiece is crucial for preventing movement or vibration during machining, ensuring dimensional accuracy.

3D Printing Accuracy

The dimensional accuracy of 3D printed parts varies depending on the printing technology, material used, and printing parameters. Factors that influence 3D printing accuracy include:

Layer thickness: Thinner layers generally result in higher accuracy, but printing time also increases.

Printing process: Different 3D printing processes have varying levels of accuracy. For example, SLA and DLP printing typically offer higher resolution and accuracy than FDM printing.

Material shrinkage: Some materials, particularly thermoplastics, can shrink during the printing or cooling process, affecting dimensional accuracy.

Post-processing: Post-processing steps, such as support removal or sanding, can also impact the final dimensions of the part.

Surface Finishing Options

This is one area where CNC machines are the clear winner. Given the right conditions, CNC machines will deliver a better-quality surface finish when compared with 3D printers.

The main reason behind the difference is the fact that 3D printers are designed for prototypes and parts that need further processing. CNC machines are made to create final products that are ready for the market, so their surface finishing capabilities are much more advanced.

CNC Machining Surface Finishes

CNC machining can achieve a wide range of surface finishes, from rough to mirror-like, depending on the tooling, cutting parameters, and post-processing techniques used.

Common CNC machining surface finishes include:

As-Machined: The surface finish directly from the machining process, which can vary in roughness depending on the cutting tool and parameters used.

Bead Blasting: Creates a matte, textured surface by propelling small beads at high velocity against the part.

Anodizing: An electrochemical process that creates a protective oxide layer on the surface of aluminum, enhancing corrosion resistance and providing a decorative finish.

Powder Coating: Applies a durable, powder-based coating to the surface, providing excellent corrosion resistance, color options, and wear resistance.

Polishing: A mechanical process that smooths the surface to a high gloss finish, enhancing aesthetics and reducing friction.

3D Printing Surface Finishes

The surface finish of 3D printed parts depends on the printing technology and material used. FDM printing typically results in visible layer lines, while SLA and DLP printing can achieve smoother surface finishes.

Common 3D printing surface finishes include:

As-Printed: The surface finish directly from the printing process, which can vary in roughness depending on the printing technology and material.

Sanding and Polishing: Manual or automated processes used to smooth the surface and remove layer lines.

Vapor Smoothing: A chemical process that smooths the surface of some thermoplastic materials by exposing them to a solvent vapor.

Dyeing or Painting: Adding color to the part for aesthetic or functional purposes.

Cutting Speed Is a Key Factor

Generally, CNC machines can cut out pieces much faster than 3D printers. However, the overall time is not dependent on the cutting rates only. The machine’s starting time and other pre-processing requirements along with other factors determine the overall speed of the process. The size also plays a part. The general rule of thumb is that for smaller pieces, 3D printers are a quicker option as they start making the part immediately. However, CNC is the right choice for larger parts.

What Are Your Post-Processing Requirements

Generally, CNC machines deliver a part that is 100% ready for the market. 3D printers are a little different. Their common applications are related to prototyping or assisting in mold creation. For both cases, a rough surface finish works just fine. Otherwise, you’ll have to further process the part before it’s ready for any other application.  

Apart from that, metal 3D printed components even have another requirement of heat treatment. Because of how 3D printing works, the developed part doesn’t have much fatigue strength and impact properties. Heat treatment allows the internal structure to set better and deliver better performance. However, it still doesn’t work as well as CNC parts.

3d printing joints

If You Need Eco-Friendliness Products

Both CNC and 3D printing materials can work with a plethora of materials. The CNC process is generally free from harmful materials while 3D printers use more thermoplastics for prototyping. If used correctly, they can be a great way to recycle the plastic that would otherwise remain in circulation for the longest time. Therefore, depending on your application and commitment to the environment, both CNC and 3D printing can potentially be eco-friendly options.  

What Is Your Manufacturing Budget

Both CNC and 3DP have some associated costs. For smaller one-off parts, 3D printers are the best choice. However, volume production requires consistent operations, and CNCs are the better options for it.

Consider the example of an automobile to understand it better. You’ll need the best quality and technical factors because of the application. Similarly, it’s natural to look for solutions that cost less because of the competition in the market and the basic fundamentals of business feasibility. Speaking of competition, it’s also integral that the process you select should be quick enough. If you are making one component while your competitors make 10 in the same timeframe, your business will naturally lose revenue in terms of opportunity costs.

Whatever you select, both cases would need significant capital and operational expenses. For smaller parts, 3DP is more cost-effective. However, the alternative can be true as you increase the production requirement or reduce the time required.

Related:

Making the Choice: CNC Machining or 3D Printing for Your Project

Choosing between a CNC machine vs a 3D printer for your project depends on your specific requirements and priorities. Below are some key questions to consider when making this decision:

Is CNC Machining More Accurate Than 3D Printing?

Yes, CNC machining generally offers higher dimensional accuracy than 3D printing. CNC machines utilize precise cutting tools and computer-controlled movements to achieve tight tolerances, often within +/- 0.0025 inches. While 3D printing can also produce accurate parts, its accuracy is typically lower than CNC machining, especially for complex geometries. For example, if you’re manufacturing a precision gear that requires tight tolerances for smooth operation, CNC machining would be the preferred choice.

Will 3D Printing Replace CNC Machining?

It’s unlikely that 3D printing will completely replace CNC machining. Both technologies have distinct advantages and limitations, making them suitable for different applications. CNC machining excels in producing high-volume, high-precision parts with excellent surface finishes, while 3D printing offers greater design freedom and is ideal for prototyping and low-volume production of complex geometries. For example, while 3D printing might be suitable for creating a prototype of a complex design, CNC machining would be a better choice for mass-producing the final product with high precision and consistent quality.

Is CNC Machining Cheaper Than 3D Printing?

The cost-effectiveness of CNC machining versus 3D printing depends on various factors, such as production volume, part complexity, material selection, and post-processing requirements. For small batches or highly complex designs, 3D printing can be more cost-effective. However, as production volume increases, CNC machining becomes more economical due to its efficiency and repeatability. For instance, if you only need a few prototypes of a complex part, 3D printing might be the most affordable option. However, if you need to manufacture thousands of simpler parts, CNC machining would likely be more cost-effective in the long run.

What are the Advantages of 3D Printing over CNC Machining?

  • 3D printing offers several advantages over CNC machining, including:
  • Greater design freedom for complex geometries.
  • Faster turnaround times for prototyping and low-volume production.
  • Reduced material waste due to the additive nature of the process.
  • Ability to create parts with internal features and cavities that are difficult or impossible to achieve with CNC machining. For example, 3D printing can create intricate lattice structures or internal channels that would be challenging or impossible to achieve with traditional CNC machining methods.

How to Choose Between CNC Machining and 3D Printing?

The optimal choice between CNC machining and 3D printing depends on several factors, including:

Part Complexity: 3D printing excels in creating complex geometries and intricate designs, while CNC machining is more suitable for parts with simpler geometries. For example, if you’re designing a customized medical implant with complex internal channels, 3D printing would offer greater design freedom. However, if you need a high-volume production of simple brackets with tight tolerances, CNC machining would be the more efficient and cost-effective option.

Production Volume: CNC machining is more cost-effective for high-volume production, while 3D printing is better for prototyping and low-volume runs. For instance, if you need to produce thousands of parts, CNC machining is generally more efficient and can achieve lower per-part costs compared to 3D printing.

Material Selection: CNC machining offers a wider range of materials, while 3D printing is limited to specific materials compatible with the chosen printing process. Consider the specific material properties required for your application, such as strength, temperature resistance, or biocompatibility.

Cost Considerations: CNC machining typically has higher setup costs but lower per-part costs for large production runs, while 3D printing has lower setup costs but higher per-part costs.

Lead Time Requirements: 3D printing generally offers faster lead times, especially for prototypes and small batches. If you need parts quickly, 3D printing might be a better option, especially for prototypes.

RapidDirect: The One-Stop-Shop for All Your Rapid Prototyping and Production Needs

When it comes to manufacturing, there is nothing that can replace experience. That’s why many businesses favor using third-party manufacturing services to ensure consistent and accurate results. Such services allow you to maintain the same level of quality in your products without spending an exuberant amount in the form of capital investment. For the best CNC machining services and 3D printing services, perhaps the most natural choice for your business is RapidDirect.

RapidDirect distinguishes itself with its versatility and focuses on quality. We have a series of stringent quality checks that maintain the standards and give you the best. Similarly, we also have one of the simplest customer onboarding processes. Our online manufacturing platform can allow you to get instant quotes for your design. Simply add your design along with all the relevant information, and that’ll be good enough to get started.  

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