Advantages and Limitations of CNC Machining

Advantages and Limitations of CNC Machining

Advantages and Limitations of CNC Machining

CNC machines have revolutionized manufacturing by improving machining quality and production speed to keep up with the ever-growing demand for complex machine parts.

These machines offer various advantages over traditional machining tools.

However, there are some disadvantages as well to CNC Machining.

So, what are the benefits of CNC Machining? What are their limiting factors? And is it worth upgrading to CNC machining?

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Advantages of CNC machining

AdvantagesLimitations
Quick machining speedHigh initial cost
Flexibility to perform multiple operationsNeed for expertise
High precision and accuracySteep learning curve
High repeatability index

Advantages and disadvantages of CNC machining

Quick Machining Speed

Unlike traditional machining, CNC machining does not require constant human interaction to execute a machining operation, thereby eliminating human limitations.

This allows for continuous production without breaks.

In traditional machining, manual labor is required to perform different miscellaneous operations like tool change, regulating speeds and feeds, etc.

Modern CNC machines can regulate the feeds and speeds and perform automatic tool changes, thereby reducing the overall cycle time.

With the advancement in technology, there are various CNC brands that provide desktop CNC machines that fit the budget of almost every user.

Furthermore, with the introduction of direct numerical control (DNC), a single operator can control multiple machines simultaneously.

When compared to NC and CNC, the DNC system improves cycle time and enhances the productivity of the machining process.

Flexibility

CNC machines are popular for their flexibility and versatility.

Although there are some alternatives to CNC machining such as 3D printing, CNC machining is comparatively more versatile in terms of being able to process several materials on a single machine.

The ability of a CNC machine to switch between different cutting tools makes it ideal for applications where different shapes are to be cut in various types of materials, such as aluminum, stainless steel, carbon steel, plastics, nylon, titanium, etc.

Precision and Accuracy

Precision cuts by Wire EDM (Source: Makino)
Precision cuts by Wire EDM (Source: Makino)

Traditional machining operations are prone to human errors, which results in comparatively lower precision and accuracy.

However, the integration of computer control, eliminates the risk of human error, making it possible to produce high-quality products with tight tolerances.

CNC machines can precisely replicate a CAD drawing and ensure perfect output, with an accuracy range of around 0.0002" to 0.0005".

The CAD (computer-aided design) model is converted into programmable codes (G-codes and N-codes), thereby controlling the cutting tool's movement, and ensuring accurate results.

Generally, the machining accuracy of a CNC router is between 0.0004”, whereas industrial grade CNC laser cutters provide an accuracy of around 0.00005”.

Furthermore, advanced CNC machining processes such as waterjet machining and wire EDM provide even higher accuracy (~0.00002"), making them ideal for intricate machining operations.

Repeatability

Repeatability is the ability to perform similar operations with exact precision and accuracy multiple times.

Even highly skilled machinists are prone to human error, and different operators operating the same machine would produce parts with different accuracies.

CNC machines eliminate the need for manual handling of tools, thereby reducing the scope for error and enhancing repeatability.

It is a critical factor for applications requiring the same results every time, such as batch and mass production.

CNC machines, such as industrial laser cutters, provide a high repeatability index of around ±0.0005 inches and, therefore, can produce an exact replica of a part multiple times, with minimal scope of error.

Limitations of CNC machining

Despite having various advantages over other machining techniques, CNC machining is prone to certain limitations.

High Cost

laser cutters and engravers prices
High-cost industrial CNC laser cutter

CNC machines are advanced machines that consist of various components such as a computer system, CNC controller, stepper motors, stepper motor drivers, gantry, cutting tools, CNC software, etc.

This increases the initial cost of a CNC machine, making it impractical for small-scale businesses.

Although there are various desktop CNC machines that can fit almost any budget, these beginner-friendly machines have limited industrial applications.

Furthermore, with the increase in the complexity of the system, the maintenance cost also increases.

Therefore, CNC machines are ideal for large-scale jobs, where efficiency and productivity have a significant effect on the machining cost.

Whereas traditional machining techniques prove to be more economical for small-scale production applications.

Moreover, there is an additional cost associated with the use of CNC in the form of expertise required to operate the machine.

Need for Expertise

Operating a CNC machine requires a specialist with knowledge of programmable codes and an understanding of the machine.

While traditional machining requires manpower to operate the machine, CNC machines require a skillful individual with technical knowledge.

This further increases the overall operating costs of a unit part produced on a CNC machine. However, in the long run, CNC machines reduce the overall cost of production by providing an economical operation.

Learning Curve

A comprehensive study with practical knowledge is required to completely understand the working principle of a complex multi-axis CNC machine.

As the part complexity increases, the use of multiple axes becomes imminent to produce favorable results. This adds to the complexity of operating the machine.

Hence, proper training is required to perform complex CNC operations, such as 6-axis machining.

For multiple axes, part cutting in different directions would require more complex codes as compared to producing parts with simple geometries.

Therefore, as the number of axes of a CNC machine increases, the complexity of machining also increases.

Should You Upgrade to CNC?

Multi-Axis CNC Machine
Multi-Axis CNC Machine

Upgrading to CNC depends on the parts that need to be produced and how fast they need to be produced.

Generally, it is recommended to upgrade to CNC machining if your application involves the mass production of complex parts with intricate geometries.

Whereas, traditional machining would be more feasible for parts with simple geometry where high precision is not the main objective.

Moreover, upgrading to CNC would be fruitful for applications where quick cycle time is of utmost importance, irrespective of the cost of equipment.

Similarly, CNC machines are ideal for applications where parts manufactured need to comply with strict standards, such as defense, aerospace, and medical industries.

However, if your application requires the occasional manufacturing of complex parts, it is recommended to outsource the job.

There are various CNC service providers that take in your requirements and deliver the machined part at a reasonable price.

Final Thoughts

CNC machining is an efficient and accurate part production technique.

It offers various advantages over traditional machining techniques, which include high-speed production rates, flexibility, and precision, making it ideal for applications ranging from DIY projects to manufacturing industries.

The use of the CNC technique however is not cheap and should generally be opted for large-scale part production requirements where accuracy is of utmost value.

Frequently Asked Questions (FAQ) 

Is a 3D printer a CNC machine?

Yes, technically, a 3D printer is a CNC machine. It basically produces parts by using the principle of additive manufacturing, where material removal is not required. However, a computer-controlled nozzle prints layers of material to produce the desired part.

What are the applications of CNC machines?

CNC machines are ideal for applications such as prototyping and 3D modeling. Apart from this, CNC machines are also used in various medical, aerospace, woodworking, and metal industries. There are various small-size and large-size CNC routers ideal for sign-making projects, similarly, CNC laser cutters are used for performing intricate cuts and engravings on different materials.

What are the types of CNC machining?

There are 5 common types of CNC machines: CNC lathe and turning machines, CNC Milling Machines, CNC Laser Machines, CNC Electrical Discharge Machines, and CNC Plasma Cutting Machines.

About John

Hey I'm John. I talk about CNCs and Power Tools at Mellowpine. I'm a CNC hobbyist who has been making CNCs and writing about CNCs for a while. I currently also work as a consultant for business owners and hobbyists setting up their own CNCs. If you have any questions related to CNC, I'd be happy to answer them. Reach me at john@mellowpine.com

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John

Hey I'm John. I talk about CNCs and Power Tools at Mellowpine. I'm a CNC hobbyist who has been making CNCs and writing about CNCs for a while. I currently also work as a consultant for business owners and hobbyists setting up their own CNCs. If you have any questions related to CNC, I'd be happy to answer them. Reach me at john@mellowpine.com

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