How CNC machined parts can reduce machining costs

CNC machining is a proven digital manufacturing process that produces high precision parts with excellent physical properties directly from CAD files.

The machining costs of CNC machines can vary considerably depending on the purpose for which you are using them. Whether you are making a single prototype or preparing for mass production, you need to check the overall budget for your project before placing an order.

  Q: How can I optimise my design and minimise costs?

  1. Add a radius to the internal vertical edge

All CNC machining milling tools have a cylindrical shape that creates a radius when cutting cavity edges.
Use a smaller diameter tool to reduce the corner radius. This means that multiple passes are required at lower speeds - smaller tools do not remove material as quickly as larger tools in one pass, which increases milling time and therefore project costs.
To reduce costs, experts recommend that the corner radius should be slightly larger than the radius of the tool used to machine the cavity. This will reduce the load on the tool and further reduce manufacturing costs.

  2. Limit cavity depth

Machining deep cavities will have a significant impact on the cost of CNC parts because of the large amount of material that needs to be removed, which is very time consuming.
CNC machining tools have a limited cutting length: typically they work best when the depth of cut reaches 2-3 times the diameter of the cavity, designing deeper cavities as special tools or multi-axis CNC systems are required This can lead to increased costs.

  3. Increasing the thickness of thin walls

Increase the thickness of thin walls to reduce CNC machining time. Unless weight is a major factor, thicker parts are more stable.
Thin parts tend to vibrate. To avoid deformation or cracking when CNC machining thin walls, multiple CNC operations at low depths of cut are required, making accurate CNC machining difficult.
For metal parts, the design wall thickness should be greater than 0.8 mm (thicker is better). For plastic parts, a minimum wall thickness of 1.5mm or more should be maintained. You will often encounter thin walls when placing holes or threads very close to the edge of the part. Make sure you also follow these guidelines when placing holes in your design.

  4. Limit the length of threads

Limit the maximum thread length to 3 times the hole diameter. For threads in blind holes, it is best to add at least 1/2 the diameter at the bottom of the hole.
Specifying longer thread lengths than necessary will increase the cost of CNC machined parts as special tooling may be required.

  5. Designing holes with standard sizes

Use standard drill sizes when designing holes. Using standard drill bits allows for fast and accurate CNC machining of holes. For non-standard sizes, holes must be machined using an end mill, which can increase costs.
It is recommended that all holes are limited to 4 times the diameter in depth. If deeper holes are drilled (up to 10 times the diameter), CNC machining is difficult and will increase costs.

  6. Mass production

Finally, there is the number of parts. The greater the number of parts, the lower the cost per additional unit. This means that a large order will increase the final cost of the part, but will reduce the unit cost. If you want to make multiple identical parts, you can reuse the same CAM programming and fixtures, or you can cut multiple parts from the same stock at once.