How to Lower CNC Machined Parts Costs through Smart Structural Design

CNC machined parts, also known as components processed using CNC equipment, represent a method of precision machining digitally controlled by a computer. This method has become increasingly prevalent in modern manufacturing.

CNC machining equipment, often referred to as CNC machine tools, goes by different names in various regions. For instance, in the Yangtze River Delta region, it's commonly called machining centers, while in the Pearl River Delta area, it's known as computer gong.

Typical CNC machine tools include:

CNC Lathe - This tool rotates the material in a lathe chuck and moves the cutting tool along two axes to create cylindrical parts.

CNC Milling Machines - These machines are used for crafting flat parts, and more advanced versions with additional degrees of freedom can produce intricate shapes. The material remains stationary while the spindle rotates with the tool, moving or rotating along three axes (sometimes four or five). In some cases, the spindle stays stationary while the material is fed into it.

CNC Drilling Machines - Similar to CNC milling machines but designed for cutting along a single axis, these machines move the drill downward along the Z-axis, without affecting the X- and Y-axes.

CNC Grinders - These machines employ a grinding wheel to achieve a high-quality surface finish. They are designed for removing small amounts of material from hardened metals, making them ideal for finishing operations.

CNC machining is widely employed across various industries due to its exceptional precision. However, CNC machining services can be relatively expensive when compared to other manufacturing techniques like injection molding, die casting, and stamping. The cost of CNC machined parts is influenced by several key factors:

Equipment Costs: These costs encompass the initial purchase price, operational expenses, maintenance, and other potential expenses like tooling and CNC system usage. More costly machines, both in terms of acquisition and upkeep, will result in pricier parts. Milling machines are typically more expensive than lathes due to their complexity and setup requirements. Consequently, it's advisable to design parts to accommodate lathe machining when possible.

Design Costs: Design-related expenses include CAD (structural and engineering design), CAE (optimization and analysis), and CAM (manufacturing programming). These costs can vary depending on the collaboration between parties and the project's volume. Larger volumes tend to reduce design costs per part.

Material Costs: Material expenses are a significant component of part costs, determined by the cost of raw materials, material quantity, and processing time. Factors affecting material costs include the choice of suitable materials based on part use and function, minimizing material usage, and the machinability of the material.

Production Volume: As the number of parts increases, the unit cost of each identical part decreases. This reduction is primarily due to the elimination of duplicate design and machine setup expenses. Design and setup costs are spread across the entire batch of parts, making it more cost-effective to produce larger quantities.

Special Requirements: Specific requirements, such as tolerance, surface roughness, and post-processing needs, can significantly impact costs. Stricter tolerance requirements and demanding surface finishes can complicate machining and raise expenses. Post-processing operations, like heat treatment and surface treatments, also contribute to overall costs.

Structural Design: The complexity of a part's structure directly affects manufacturing costs. To minimize costs and enhance efficiency, consider the following design principles:

Avoid thin-walled designs and favor thicker walls for stability and cost-effectiveness.

Ensure that design features are compatible with CNC machining and avoid 90°internal angles.

Use larger internal corner radii to reduce machining time and tool wear.

Limit the depth of cavities to avoid excessive material removal and machining challenges.

Reduce the use of curved structural features to save time and costs.

Keep thread lengths to a minimum to avoid unnecessary machining.

Design standard-size holes for faster and more accurate machining.

Minimize the number of CNC machine setups to reduce manual handling and custom fixturing.

Avoid unnecessary text and lettering, but if required, follow cost-effective techniques such as silk-screening and laser engraving.

By implementing these design practices, you can reduce the cost of CNC machined parts while maintaining quality, making the manufacturing industry more competitive and responsive to market demands.