Processing costs that should be considered when designing with chamfers and fillets

Although the chamfering and rounded corners are beautiful and easy to design, these designs will increase the processing time and production costs of the CNC turned parts. Machining design requires knowing how the parts are manufactured and the skills to adjust the design to keep production costs low.

With this in mind, before adding chamfers or fillets to your design, you should ask yourself the following questions:

1. What is the function of chamfering or rounding?
2. Is the chamfer or fillet necessary for the part to work?
3. Under the planned production quantity, is it cost-effective to increase this design?
4. How to check the tolerance?

To help you better understand why these design and cost considerations are important, let's look at some examples.

First, let us compare how to make fillets and chamfers during CNC machining. Chamfering usually uses tools such as point drills, countersinks or chamfers. Point drill or countersink tools are used to make internal chamfers, and chamfer tools are used to make external chamfers.

Filleting is usually achieved with end mills that machine the contour of the part. If the fillet is along the edge of the part, it can be made with a fillet end mill. But setting them can be very time-consuming, and the tool must blend the radius to the top and side surfaces of the part so that there are no steps.

Increasing chamfers and fillets and the need for a higher level of precision and quality will significantly increase your processing time, and longer processing time means higher production costs. Before you add a chamfer or fillet, consider whether it is necessary for the function of the part and whether it is worth the cost increase.

Another factor that affects costs is output. If it's just proofing, the cost of each part is already very high in addition to the cost of rounding and chamfering. However, if mass production is carried out, the cost of each part does not increase much, which is cost-effective. In addition, for mass production, you may use casting or forging processes, in which case rounded corners are not only cost-effective, but necessary.

If the part must be chamfered or rounded, then the next consideration is how to machine the part while keeping costs low. The smaller the tolerance, the higher the cost of the part.

If the chamfer diameter is marked with three decimal places, it means that strict tolerance requirements require more precise processing equipment and more difficult quality inspections.

You can consider changing the chamfer to two decimal places to ensure accuracy, or simply remove the chamfer from the hole label to make things simpler and probably cheaper. If the exact size is not important, you can remove the chamfer feature from the solid model and add a note to the drawing stating "remove all sharp edges". Alternatively, it can be called using the minimum and maximum feature sizes and large tolerances.

Chamfering is cheaper than rounded corners, and you can even change rounded corners to chamfered corners without affecting the function of the part. The fillet radius tool requires more setup time than the chamfer tool, because you need to ensure that it blends with the surface connected by the fillet. In addition, the processing time required for chamfering is shorter than that for rounding, because the rounding needs to be processed multiple times with a ball end mill. Saving time is saving costs!

It takes practice and experience to understand how the design of parts affects processing time and cost, but through quick-enhanced process recommendations, you can be one step ahead in this regard.