Some operational techniques for CNC lathe machining

As we all know, most precision parts and auto parts are produced by means of CNC lathe machining, and there are many precautions in the CNC lathe machining process. Today, we will introduce some operation skills.

Programming Skills for CNC Lathe Machining

Most powerful enterprises have high requirements for the precision of machined parts, so the following points should be considered when programming for machining on CNC lathes:

1. Part Machining Sequence:

Drill first, then plane (to avoid material shrinkage during drilling);

Perform rough machining first, then finish machining (to ensure the precision of the part);

Process large features first, then small ones (to ensure that the surfaces with small tolerance specifications are not scratched and to avoid part deformation).

2. Determine appropriate speed, cutting speed, and cutting depth according to material hardness:

For carbon steel materials, high speed, high cutting speed, and large cutting depth are selected. For example: for 1Gr11, select S1600, F0.2, and a cutting depth of 2 mm;

For die steel, low speed, low cutting speed, and small cutting depth are chosen. For example: for GH4033, select S800, F0.08, and a cutting depth of 0.5 mm;

For titanium metal materials, low cutting speed, high feed rate, and small cutting depth are adopted. For Ti6, for instance, S400, F0.2, and a cutting depth of 0.3 mm can be selected. Take the machining of a part with material K414 (a special hard material) as an example: after multiple tests, the parameters S360, F0.1, and a cutting depth of 0.2 were finally determined to produce qualified parts.

Tool Setting Skills for CNC Lathe Machining

Tool setting in CNC lathe machining includes tool setting with a tool setter and direct tool setting.

First, set the center of the right end face of the part as the tool setting point. Each necessary CNC tool is set with the center of the right end face of the part as the tool setting point; when the tool touches the right end face, input Z0 and click "Measure"—the tool compensation value will automatically record the measured value, which represents Z-axis tool setting. For X-axis tool setting, perform a trial cut: use the tool to turn a small part of the outer circle, measure the turned outer circle (e.g., x is 20 mm), input x20, and the tool compensation value will automatically record the measured value—at this point, X-axis tool setting is completed. With this tool setting method, even if the CNC lathe is shut down, the tool setting value remains unchanged after restarting, which can be used for long-term production of the same part. During mass production, there is no need to reset the tool after shutting down the lathe.

Debugging Skills for CNC Lathe Machining

After programming the part, simulate the machining with the tool and conduct a cutting test. To prevent problems in the program, the cutting test and simulation machining of the tool should be carried out. Specifically, perform a forward cutting test, simulate the machining process, and repeatedly verify the tool path and parameters to ensure the correctness of the program.

On Completing Part Machining

After the first sample achieves successful tool radius compensation, mass production can be carried out. However, the qualification of the first sample does not necessarily mean that all parts will be qualified. During machining, due to differences in materials, the CNC tool will wear—softer materials cause less tool wear, while harder materials lead to faster tool wear. Therefore, during machining, frequent measurement and inspection are necessary, and timely tool adjustment (increasing or reducing the cutting depth) is required to ensure part qualification.

Take a part as an example: the material is K414, and the total machining length is 180 mm. Due to the special nature of the material, the CNC tool wears quickly during machining. From the start to the end, tool wear will definitely cause a slight deviation of 10–20 mm. Therefore, a 10–20 mm allowance should be artificially added in the program to ensure the part is qualified.

The operation technology of CNC lathe machining is a process from shallow to deep and cannot be mastered overnight. It is based on mastering the basic operation knowledge of CNC lathes, basic precision machining knowledge, and basic programming knowledge. Moreover, the operation skills of CNC lathe machining are not fixed; they require the operator to fully combine imagination and practical ability, and it is a creative labor.