Posted December 15, 2020

What Are The Advantages of CNC Machining Over Conventional Machining?

Close up of CNC machine at work.

Any manufacturing engineer knows that a small discrepancy in tool movements can have significant consequences. So, while CNC machining shares basic principles with conventional machining, it’s essential to understand the key differences. CNC machining operates through computer software that controls and optimizes cutting, milling, drilling, and other types of tools while overseen by a trained and certified programmer. In contrast, conventional machining operates through the machinist alone. 

Computer numerical control application allows machining tools to respond to multiple commands that can produce consistent, repeatable, and complex machining of large numbers of parts for applications ranging from aerospace to consumer packaged goods. While conventional machining can match some aspects of design complexity, the reliance on human control introduces a higher potential for error. It decreases the capability to produce large batches of precisely consistent parts. Each of these differences translates into advantages of CNC over conventional machining.

The Advantages of CNC Over Conventional Machining Start with Consistency

In either CNC or conventional machining, the time needed to bring more than one high-quality part to market depends on the ability to produce consistently precise tolerances. Inconsistent accuracy for the tolerances specified on a design causes the rejection of components because of low quality. That lack of consistent accuracy may trace back to selecting the wrong type of cutting tool, a machine setting, or an operator error. 

Addressing accuracy problems interrupts production and may lead to delays. CNC machining assures the accuracy that conventional machining cannot attain through the use of geometric dimensioning and tolerance standards to a design.

No matter how experienced, a human operator can’t analyze the hundreds of possible manufacturing variables based on a part’s geometry or use that data to select the optimal tool from an extensive library. CNC machining protects against inconsistency through seamless transitions between CAD models and the CAM software that automates machine operations for fabricating a part, with minimal human input.

Compared to CNC machining, conventional machining cannot provide the consistency needed to produce rapid prototypes or large batches of precision components for an aerospace application, for example. Each machining operation—from choosing the correct parameters, performing the rough cut, placing the part in a workholding, profiling the edge of the part, and surface finishing—requires quality control checks and precision. 

For conventional machining, the need for human action in each step of the operation decreases precision and consistency, especially in determining the workholding for complex parts. CNC machining requires significantly less time and optimizes accuracy with cutting-edge technology while minimizing human error in production runs.

CNC Machining Aligns with Design for Manufacturing and Assembly

Design for manufacturing (DFM) follows process, design, material, environment, and testing principles that can help deliver high-quality precision parts at lower costs. Each of those principles shows up early in the design process, impacting engineers, material suppliers, and manufacturers. Applying DFM to a specific part design establishes a feedback loop for considering design changes without adding expenses to a project. Technology-enabled CNC machining can quickly deliver DFM feedback or DFM analysis to customers.

If a designer, an engineer, or a manufacturing team requests a change in a product specification, the multiple manual methods needed to execute that change within conventional machining adds time and cost to the project. An operator must select the proper machine tools, adjust the tools for the correct positioning, and make decisions about workholding and cutting methods to implement change requests. 

CNC machining offers a flexible solution to design changes. The software can quickly and efficiently apply multiple solutions to the change request, ensuring the correct coordinate directions and dimensional relationships.

While conventional machining can produce smaller production quantities or meet hobbyist design specifications, it typically lacks the precise computing processes that minimize assembly operations or complexity. The overhead and labor costs associated with conventional manufacturing can make it more difficult to gain valuable design insights through the DFMA process. 

CNC machining shortens product development cycle time and reduces costs through its flexibility with design changes, well-defined standards, and highly accurate software. Manufacturing cycles become shorter through tool performance, custom workholding, and low-probability for cutting deformation.

CNC Machining Offers Long-term Cost Advantages Over Conventional Machining

On the surface, conventional machining seems to serve as a lower-cost alternative to CNC machining. Conventional machining offers a lower starting cost for companies that wish to add in-house machining capabilities to their business. The upfront costs of owning and operating CNC equipment may range higher than the same expenses for conventional machining equipment. But cutting costs in the short-term isn’t a sustainable long-term solution.

Conventional machining is useful for single custom designs or small quantities, but matching the precise specifications required for an aerospace or defense application with conventional machining requires longer set-up and production times. Meanwhile, CNC machining reduces costs for larger production runs with no variation from one part to another. 

It’s also worth noting the difference in the expertise required for CNC vs. conventional machining. Conventional machining requires expertise that depends on extended training and long experience with operating, adjusting, and maintaining equipment. Operating CNC equipment requires knowledge about safely working and supervising complex machines and processes and using CAM software and reading, interpreting, and compiling codes. Along with preparing CNC machines for different operations, CNC operators must understand specifications that involve geometric tolerances and the ability to inspect and measure finished parts that adhere to design specifications.

Operating CNC equipment requires knowledge about safely working and supervising complex machines and processes and using CAM software and reading, interpreting, and compiling codes.

While it seems CNC machinists require a higher level of expertise, CNC machines produce more products in less time and with fewer operators. Overall, CNC machining merges operator skill with software and tooling flexibility to produce repeatable precision within short timeframes and lower costs.

If you’re ready to realize the advantages of CNC over conventional machining for high-quality precision parts, contact the experts at Plethora. We’re an ISO 9001-certified CNC machine shop specializing in component manufacturing—partnering together to execute your design strategically. Get started today by uploading your design files to Quote My Part, or give us a call at 415-726-2256.

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The Plethora Team

The Plethora team is your go-to CNC manufacturer for hardware done right the first time. We have the tools and experience needed to create high quality custom parts quickly and with precision, whether you need a prototype or production run.