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CNC Machining: DFM Principles & Advantages for Efficient Manufacturing

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Home / CNC Machining / CNC Machining: DFM Principles & Advantages for Efficient Manufacturing

CNC Machining: DFM Principles & Advantages for Efficient Manufacturing

Jiga helps you source high-quality, cost-competitive custom parts faster by partnering directly with vetted manufacturers.

Table of Contents

Whitepaper

The complete guide to
Design for Manufacturing and Assembly

dfm whitepaper preview

Tips to simplify designs

Practical steps to early DFM integration

Strategies to choosing suppliers

Actionable advice from industry leaders

Whitepaper

The complete guide to
Design for Manufacturing and Assembly

dfm whitepaper preview

Tips to simplify designs

Practical steps to early DFM integration

Strategies to choosing suppliers

Actionable advice from industry leaders

Complex aerospace component designed for 4+ axis machining, featuring optimized toolpaths, minimal tool changes, easy fixture mounting, and high strength with low weight.

CNC machining is the automated and programmable derivative of traditional manual machining, evolved out of a long development process that began with the Jacquard looms of the early 18th century. CNC machine tools are diverse and range from the simplest 3 axis part motion, spinning cutter to intricate and flexible 12 or more axis machines that can function as both mill, lathe and even automatic welder and cutter. 

Their role is primarily in single part and low volume traditionally, but as capabilities and automation improve, the creep of CNC services into mass production is developing fast. This transition massively increases the pressure towards effective use of DFM throughout the design process, to be volume ready.

Advantages of CNC machining in manufacture

Using CNC machined components in a design delivers various pivotal design and product wins that make effective design for CNC machining a central capability in the designers arsenal;

  • CNC machines can produce highly accurate and repeatable parts with tight tolerances, ensuring consistency and compliance in every part. Repeatable and identical parts with low errors and high quality are maintainable across large production runs.
 
  • Machining parts on CNC equipment allows low labor, 24/7  operation, with minimal human intervention, delivering high productivity and fast turnaround times.
 
  • CNC machines can work with an astonishing range of materials – metals, plastics, composites, ceramics and even natural materials like wood, stone etc., making the capability central to many production environments.
 
  • These processes can deliver intricate and complex geometry, within certain limitations. Equivalent outcomes are difficult or impossible to achieve repeatably with manual machining.
 
  • Although the initial setup cost can be relatively high and often involves custom fixtures and programming, CNC machining removes considerable downstream and inflexible labor costs, relative to manual machining. Typically material waste and scrap rates are improved, moving the errors into virtual and simulated operations..
 
  • CNC machines can be readily programmed to produce divergent components in quickly changed materials, rendering the method suitable for both prototyping and full-scale production runs.
 
  • Automated control of the process minimizes the risk of human error, once setup and programming are validated, delivering repeatable quality in manufactured parts.
 
  • CNC machines operate with enclosed/interlocked cutting environments and automated processes, reducing, presenting low risk of accidents and injuries in the workplace.
 
  • CNC machining can seamlessly scale from prototypes to high-volume production runs without sacrificing quality or efficiency.
Complex aerospace component designed for 4+ axis machining, featuring optimized toolpaths, minimal tool changes, easy fixture mounting, and high strength with low weight.
This component exploits the capabilities of 4+ axis machining to deliver a complex but highly machinable part for an aerospace application. It requires optimized toolpaths to be cost effective, it is designed to exploit the equipment capabilities of the machining center, and it has been designed for easy mounting to a fixture for machining. Further, it uses the minimum number of tool changes to complete the parts and it delivers low weight, high strength in the final execution.
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DFM Principles

The guidelines that must drive the part design process to be CNC ready result in easier setup and manufacture of lower cost parts. The design limitations imposed by machine-readiness are not extensive, but there are rules that must not be broken.

Select materials with care

Consider machinability when selecting materials – harder materials means slower cuts and lower throughput.

Where post hardening is required, after machining, allow for distortions that may result by stress relieving before machining and my post processing using grinding or EDM approaches to reimpose precision.

Simplicity is key

Minimize complexity by simplifying designs helps to reduce and moderate intricate details that otherwise increase machining time and cost. Use simple geometries and avoid deep cavities or sharp internal corners.

Design holes to standard sizes that match readily available drill bits and limit the variety of diameters in a part to reduce tool changes. This speeds up throughput considerably.

Use minimalist tolerancing

Specify tolerances that are as tight as absolutely necessary for function and fit. Overly tight tolerances dramatically increase machining time, programming complexity and component cost.

Take care with geometry

Maintain consistent wall thickness to reduce stress concentrations, reduce warp risk, and improve part strength. This is highly relevant in some materials, but the rule is far from universal as many materials can be stress relieved before machining to improve the tolerance of variations in section weight.

Design parts to avoid deep pockets, which are often challenging and time-consuming to machine. Where deep pockets are necessary, consider making them stepped in profile or open and cut through allowing two-sides cutting.

Add filets to internal corners to distribute stress and reduce the likelihood of cracking, and allow cutting tools to navigate the part more smoothly in transitions. Aim for filets that use a tool that is suitable for.

Plan the approaches to part clamping and machining order in the early design phase, to avoid later difficulties and extended machining times

A vise securely clamped to a workbench, featuring T-slot clamping mechanisms for added stability and precision during machining tasks.
Take care to plan holding methods as part of the design process, so that the machinists setup tasks are simplified.

Plan for secondary operations, such as deburring or surface finishing, and design parts to minimize these processes whenever possible.

Toolpath efficiency

Plan tool-paths in the design to minimize the number of tool changes required. Try to design so that you cluster similar features, to allow for continuous machining with the same tool, improving toolpath efficiency.

Make hole sizes and internal radii consistent to reduce tool changes

Conclusion

Incorporating DFM principles in parts prepared for CNC machining can greatly enhance the efficiency, quality, and cost-effectiveness of the manufacture. By optimizing material selection, part geometry, design-planned toolpaths and machining strategies, you can minimize production time and reduce material waste.

Effective use of DFM ensures that the designs are compatible with CNC capabilities, allowing for precise, repeatable, and high-quality production. On that basis, it is important to plan according to the axis-count of the expected supplier/machine, to minimize the required setups and repositioning error sources. Additionally, adhering to DFM guidelines facilitates smoother transitions from prototyping to full-scale production, ensuring that parts are not only manufacturable but also economically viable.

CNC machining bridges the gap between design intent and practical manufacturing, leading to superior product outcomes and a competitive edge in the market. Effective application of the core principles of DFM can greatly improve machinability and cost effectiveness.

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Jon
Jon is a dynamic and accomplished professional with a rich and diverse background. He is an engineer, scientist, team leader, and writer with expertise in several fields. His educational background includes degrees in Mechanical Engineering and Smart Materials. With a career spanning over 30 years, Jon has worked in various sectors such as robotics, audio technology, marine instruments, machine tools, advanced sensors, and medical devices. His professional journey also includes experiences in oil and gas exploration and a stint as a high school teacher. Jon is actively involved in the growth of technology businesses and currently leads a family investment office. In addition to his business pursuits, he is a writer who shares his knowledge on engineering topics. Balancing his professional achievements, Jon is also a dedicated father to a young child. His story is a remarkable blend of passion, versatility, and a constant pursuit of new challenges.

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