How to design parts for cnc machining?

2.2 Process Design Methods of CNC Machining

The task of process design is to clearly identify which parts of a component require CNC machining, the processes they will undergo, and how to determine the sequence of these processes. Typically, the following methods are used to determine the steps in the machining process:

According to the Tools Used:

To reduce the number of tool changes and save time, steps can be determined by grouping operations that use the same tool together. All steps that use the first tool are completed first, followed by steps using the second tool, and so on.

Flat Hole Parts:

These are generally machined using point-to-point and linear control CNC machines. When devising the work steps, the focus is on controlling machining precision, yield rate, and the time required for machining.

Rotational Parts:

These are typically machined using CNC lathes or grinders. When machining on a lathe, the process often involves rough machining with significant material removal. CNC lathes frequently use low-intensity tools to machine small grooves, making oblique cutting suitable to avoid chipping.

Flat Contour Parts:

These are usually machined with CNC machines, where the method should emphasize controlling the directions of cutting in and out. For irregular part contours, CNC machines with linear and circular interpolation functions should use the shortest possible line or arc segments to closely approximate the part’s contour. The optimal solution minimizes the number of segments while keeping errors within acceptable limits.

Three-Dimensional Contour Parts:

Some parts, due to their shape and surface quality requirements, have lower strength. The machine’s interpolation method can address this issue. For instance, when machining straight-walled surfaces of aircraft beams, a three-axis machine might only use a ball-end mill with lower efficiency. However, a four-axis machine can employ a cylindrical milling cutter with higher efficiency than a ball-end mill.

By considering these factors, the process design for CNC machining can be optimized for efficiency, precision, and overall productivity.

2.3 The Process Design of CNC Machining

The general process of CNC machining involves reading part drawings, process analysis, process planning, CNC programming, and program transfer. Before CNC machining begins, detailed part design drawings should be prepared. When machining parts on a CNC machine, one should first analyze the structure, material, geometric shape, size, and precision requirements of the parts according to the pre-drawn part drawings. The results of this analysis serve as the basis for determining the CNC machining process.

To establish the CNC machining process, it is crucial to understand the content and principles of CNC machining thoroughly. The process involves:

1. Designing the Machining Process: This includes selecting the machine tools and necessary equipment for machining the parts, determining the positioning and clamping of the parts, establishing the steps and sequence of operations, and specifying the usage methods and cutting dimensions for each tool in each step.
2. Documentation and Verification: It is necessary to complete the CNC machining process documents, machining programs, and program verification.

From practical experience, simply following the pre-established CNC machining program often has many shortcomings. This is because the personnel performing the machining might not fully understand the specific steps and principles of the program, nor the intent of the programmer. Usually, the programmer needs to provide on-site guidance to the machining personnel during part machining. While this can work for small-batch production, it poses significant issues for long-term, large-quantity production.

Therefore, it is crucial for programmers to provide adequate supplementary explanations and clarifications for the more complex and less intuitive parts of the CNC machining program. This is particularly important for CNC machining programs that are intended for the long-term, large-scale production of parts.

2.4 Issues to Pay Attention to in CNC Machining Process Design

In CNC machining, it is essential to prevent unnecessary friction between the tools and the parts. Therefore, it is crucial to clearly emphasize the machining paths of the tools in the process design programming. This ensures that the operators fully understand the machining paths before starting the machining process. Additionally, the clamping positions of the parts should be properly set to minimize potential issues.

Moreover, any adjustments to the program, tool paths, or positions must be communicated to the operators in advance to prevent unnecessary problems.