Computer numerical control (CNC) offers the capability of controlling the various machining processes in a precise manner, leading to the potential for cost savings in the overall production process. CNC machining is generally worth the investment because the processes render precise results that meet specific requirements.

Industries such as hydraulics, medical, automotive, aerospace, and oil & gas, benefit from the quality and consistency afforded through CNC machining. This article discusses cost drivers for CNC machining metal parts, and provides possible solutions for reducing those costs.

What Factors Drive CNC Machining Costs?

CNC Machining is an integral process for completing precision components for many industries. The cost drivers for CNC machining metal parts will depend on a number of factors, including:

• Stage of Development: A component that is in the prototype and development stage may require several passes with various CNC machines to finalize the specifications, which could increase initial costs. On the other hand, a well-established workpiece that has all the requirements in place will simply require the CNC operator to pull up and program the specifications from previous runs.
• Design Complexity: A more complex design will require more precise machining. Utilizing advanced machines, such as 5-axis machines in place of 3-axis machines, could serve as cost drivers. In general, if it takes longer to machine a part, it will cost more.
• Number of CNC Processes Required: Some pieces require more machining processes to achieve the desired outcome. As a rule, prices increase as more machining processes are involved.
• Type of Metal Involved: The material being formed may add to the cost of machining. Some materials are more expensive to purchase, and harder materials may take longer to machine.
• Total Quantity: It takes a specific amount of time to set up the CNC machines, and these costs are usually spread over the total production run. A small quantity may not be very cost-effective, while larger runs will be able to realize economies of scale by spreading out the costs over a higher quantity.
• Customer Specifications: The design plans may specify additional requirements, such as very tight tolerances or thin walls. This could drive up the machining costs if specific tools and additional processing time are required.
• Finishing Requirements: Although a material finish can improve the part’s appearance, or make it more corrosion-resistant, this can also drive up the machining costs.

How to Effectively Reduce CNC Machining Costs

Although some requirements simply cannot be changed, there are certain considerations in start-up expenses, machining time, and material costs, which can help reduce overall costs. Steps that specifiers and engineers can take to effectively reduce CNC machining costs include:

• Design Simplification: Design parts with features that can be machined easily. Holes, threads, slots and contours that can be made with standard machining tools are more cost-effective than those that require custom hole or thread sizes.
• Rounded Corners: Creating a sharp, 90-degree corner requires additional machining processes. Changing an internal corner design from 90-degree to rounded can lower CNC machining costs. Another step would be to make the radius of internal corners at least one-third the cavity depth.
• Cavity Depth: Removing material through CNC machining in order to create a deep cavity can be a time-consuming and expensive process. In general, CNC cutting tools work most efficiently when creating cavities that have a depth of between two and three times their diameter. Try to limit the depth of cavities, where possible, to four times their length.
• Wall Size: Thinner walls will take more time to machine because of their fragility, and susceptibility to fracturing. Depending on weight requirements, walls should be thicker than 0.8 millimeters. Place holes and threads strategically to reduce fracturing potential.
• Thread Length: Threads that are longer than 1.5 times the hole diameter may require special tools to create them. Set a maximum length of three times the diameter to optimize cost factors.
• Material Machinability: Unless there are specific reasons to choose a particular material, try to specify those which are easily machined. Some metals yield more easily to the machining process, thereby reducing time and cost factors.
• Tolerances: Review your specifications to determine whether tolerance requirements are absolutely necessary. Advanced precision required in a design may come at a higher price. While some industries require strict adherence to specifications, cost savings can be realized if your tolerances can be more flexible.
• Quantity: Place larger bulk orders, when possible, to save machining set-up time.

Learn More About the Factors That Drive CNC Machining Costs

Catering to sectors including the automotive, medical, hydraulics, aerospace, and oil & gas industries, Impro provides a wide array of precision CNC machining solutions to customers. If you are interested in finding more about our machining processes and capabilities, please contact our team of experts today.