How to reduce cnc machining costs?

In the field of precision manufacturing, CNC machining is like a magical engraving master, capable of transforming ordinary materials into precision parts. But do you know? What seems like a simple part design actually hides many "codes" that affect costs. Mastering these cost-saving design tips for CNC machining can not only enhance the performance of your parts but also significantly reduce production costs!

Using widely available materials and off-the-shelf parts gives you the benefits of mass production, even in small-batch production, which can significantly reduce machining costs.

Some of the other benefits of using standard components include:

Simplified inventory management

Easier purchasing

Avoiding tooling and equipment investments

Faster manufacturing cycles

Standard components can be used to handle tasks such as inventory management and purchasing more efficiently, leading to cost savings.

Added complexity means added cost. If your product design is particularly complex, it may be worth breaking down the component into several pieces for CNC machining. Although this will add to the cost of assembly, it may be more cost-effective overall than trying to machine a single component.

Design optimization is critical to reducing CNC machining costs. It involves simplifying the design and minimizing the number of operations required in the machining process.

#1 Use rounded internal corners

CNC machining tools naturally leave rounded internal corners as a result of their shape. The narrower the internal radius, the smaller the tool required and the higher the number of passes that will be needed at a slower speed. For the most cost-effective result, ensure your product design has an inside corner radius has a length to diameter radius of 3:1 or less.

#2 Avoid deep internal cavities

Processing deep cavities will greatly affect the cost of CNC parts because a large amount of material needs to be removed and it takes an extremely long time. The cutting length of CNC tools is limited. The best processing effect is achieved when the cutting depth reaches 2 to 3 times its diameter. For instance, an ø12 milling cutter can safely cut cavities up to 25mm deep.

Cutting deep cavities (five times or more of the tool diameter) can lead to problems such as tool sagging, tool skew, difficult chip removal and tool breakage. Therefore, special tools or multi-axis CNC systems are required. In addition, when cutting the cavity, the tool must be tilted to the correct cutting depth, and a smooth entry requires sufficient space.

Limiting the depth of all cavities to five times their length (i.e., the maximum size on the XY plane) can achieve the minimum processing cost.

#3 Avoid high and thin walls

To machine parts with thin walls the speed of the CNC machining action must be slowed right down, increasing machining time. Thin walls can also mean that the usual tight tolerances that CNC machining is renowned for cannot be held. Walls should have a minimum thickness of around 0.794mm for them to be feasible for CNC machining, and if the product design requires a thinner wall then it may be better to look at sheet metal fabrication as an alternative manufacturing method.

#4 Avoid too small an Radius

CNC milling cutters have a cylindrical shape. When cutting interior walls, a radius will appear at the vertical Angle. Small tools can perform multiple operations at a lower speed to achieve a small radius, which will result in more time and higher costs.

Therefore, when you design parts made by CNC machining, it is best to increase the cavity depth radius and use a similar radius for the inner edge. If you do not provide 2D drawing files specifically stating that the corners at the right angles need to be cleared, our company will process all the right angles in the inner cavity of the workpiece according to the following rules to the minimum R.

Suppose the tool diameter is ∮Dmm, the maximum depth of the inner cavity is Hmm, and the minimum inner Rmm is R. The formula is R=(H/10)+0.5, ∮D=H/5. For example, if the inner cavity depth is 30MM, the minimum inner R can be processed to R3.5mm=(30/10)+0.5, and the corresponding tool is ∮6=30/5. At present, the minimum internal R we can achieve is R0.5 and the depth is ≤3mm. The smaller the internal R, the smaller the tool required, and the higher the processing cost will be.

If you need to keep the right Angle of the workpiece, please provide a 2D drawing file for annotation and explanation. It requires a discharge machine for corner cleaning (corner cleaning needs to be done by CNC machining the copper core first and then by discharge machining on the discharge machine, which is relatively costly), or change the structure of the workpiece to make an R corner to avoid empty Spaces, and then directly process it by CNC, which is relatively low-cost. If both sides of the workpiece are through holes, they can be cut and processed on an online cutting machine to clear the corners, but the cost is relatively high.

Design optimization is critical to reducing CNC machining costs. By simplifying the design and minimizing the number of operations required, you can reduce the time and effort needed to machine the part. This can be achieved by:

Removing Unnecessary Features: Simplify the design by eliminating features that do not add value to the part's functionality.

Using Standard Tool Sizes and Tolerances: Standardizing tool sizes and tolerances can reduce the need for custom tools and minimize machining time.

Optimizing Part Layout: Arrange parts within the raw material to minimize waste and reduce material costs.

Considering Alternative Manufacturing Methods: Explore other manufacturing methods, such as precision stamping or sheet metal fabrication, which might be more cost-effective for specific designs.

Evaluate the necessity of surface treatments like chemical film, which can enhance component properties but also increase machining costs.

Design for the Most Cost-Effective CNC Machining Process

Each manufacturing technology has its advantages and disadvantages. During the design phase, you can utilize these advantages to reduce costs. Innovative designers will learn the unique characteristics of each manufacturing process and then take advantage of them.

Choose the most cost-effective option if your design is manufacturable via multiple technologies.

The different CNC technologies, from most cost-effective to least, are:

Laser cutting

Turning

Milling

3-AxisTurn-millingMilling

5-Axis

The expected production level is an essential consideration in the design, as specific manufacturing processes are better suited for small-batch or large-scale production. 3D printing, for example, is usually best for low batch sizes (< 10), while injection molding can be best for large batch sizes (>1,000).

Careful selection and maintenance of machine tools are essential to minimize expenses associated with adding new tools when existing ones fail.

Standard CNC machining tolerances are usually around +/-0.127mm, but +/-0.005mm can be achieved in many cases, with even tighter tolerances on critical areas. However, to avoid adding unnecessary cost to your parts, it is recommended that you specify only the critical surfaces or features with numerical tolerances and leave the rest of the model within a standard tolerance range. This will keep your costs to a minimum.

►In order to reduce communication costs and avoid machining errors, it is recommended that when designing, the thread be designed according to standard borehole inner diameter and rolling outer diameter, and the thread parameters be expressed completely, and when placing the order as much as possible, the inner and outer thread workpieces be processed in the same order;

►Each engineer drew a 3D drawing with a different diameter of the bottom hole of the thread. For example, the standard diameter of the bottom hole of M3x0.5 is ∮2.5 (see the figure below). When programming, drill the bottom hole directly according to the bottom hole ∮2.5 and then tap it on the automatic thread machine. If the bottom hole is drawn as ∮3, the bottom hole will be machined too large and cannot be tapped (some can be remedied by fitting a thread sleeve).

►Strong threaded connections occur in the first few threads, sometimes no very long thread length is required at all, long threaded holes may require special tools and more machining time and cost, thread length is recommended not to exceed 3 times the hole diameter. When the threaded hole is a blind hole, it is recommended to leave at least half the diameter of the hole without threads at the bottom of the hole.

Choosing the best material that delivers performance at a reasonable cost is vital. In addition to machining fees, the raw material cost is a significant component of the overall expenses for CNC machined parts. There is no single material that is best for saving money. In the long run, the most economical material meets the part's specifications while offering the lowest combined cost of materials, processing, and service over the product's lifespan.

Choosing the right tool can significantly affect machining efficiency and cost. For example, using a tool with a larger diameter can remove material faster and reduce machining time ‌

Different tool materials and coatings affect their durability and cutting efficiency. Carbide tools, for example, are more expensive but have better durability and cutting efficiency

The various operations associated with CNC machining can drive up costs. That's why it's always best to design your part to avoid secondary operations as much as possible. Deburring, inspection, plating, painting, heat treating, material handling, and other processes can add up to more than the main manufacturing cost. Therefore, these processes should always be considered in the design phase. For instance, bead blasting can be a cost-effective surface finishing option, but it should be used judiciously to avoid unnecessary expenses.

Choosing the right CNC machine for your needs is critical to optimizing CNC machining costs. Different types of CNC machines have varying fees, and selecting the right machine can help reduce costs and improve efficiency.Consider the start-up costs, including initial expenses related to CAM programming and process planning, which can be significant but diminish with higher production volumes.

When selecting a CNC machine, consider the following factors:

Type of Material: Different materials require different types of CNC machines. For example, harder materials like stainless steel or titanium may require more advanced machinery.

Design Complexity: Intricate designs may require more advanced machinery and specialized tools.

Production Volume: Higher volume orders often require more advanced machinery to meet demand.

Budget: Depending on the type and complexity of the machine, CNC machines can cost from $20,000 to over $150,000.By considering these factors and selecting the right CNC machine for your needs, you can optimize CNC machining costs and improve efficiency.

Teamwork is essential in any line of work, and that's especially true for CNC machining projects. Work with the manufacturer and ask if you have any doubts about the design. After all, getting the design wrong adds to costs.

Similarly, let the manufacturing team focus on what they do best. On drawings, specify only the final characteristics needed; do not specify the process. Allow manufacturing engineers as much latitude as possible in choosing a process that produces the required dimensions, surface finish, or other required characteristics.

With HP Machinery, our design and engineering experts check the manufacturability of your design. After, a fully-vetted supply chain ensures you get the high-quality parts you need.For sophisticated production orders, experts will work with you to develop, align, and supervise a manufacturing and quality plan from start to finish – keeping you updated at every step.

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