CNC Knowledge: CNC lathe operating skills and experience

Programming skills

Due to the high precision requirements for processed products, considerations when programming are:

First, consider the sequence of processing parts:

1. Drill holes first, then flatten the end (to avoid material removal during drilling);

2. Rough turning first, then fine turning (this is to ensure the precision of the parts);

3. Process parts with large tolerances first, and process parts with small tolerances last (this is to ensure that the surface of small tolerances is not scratched and to prevent the parts from deformation).
According to the hardness of the material, select a reasonable rotation speed, feed rate and cutting depth: 1. Choose high rotation speed, high feed speed and large cutting depth for materials made of carbon steel. For example: 1Gr11, choose S1600, F0.2 and cutting depth 2mm; 2. For carbide, choose low speed, low feed and low cutting depth. For example: GH4033, choose S800, F0.08 and cutting depth 0.5mm; 3. For titanium alloy, choose low speed, high feed and low cutting depth. For example: Ti6, select S400, F0.2, cutting depth 0.3mm. Take the processing of a certain workpiece as an example: the material is K414, which is a super-hard material, after many tests, S360, F0.1 and cutting depth of 0.2 were finally selected before before a qualified part is processed.

Knife Adjustment Skills

Tool setting is divided into tool setting instrument setting and direct tool setting. The tool setting techniques mentioned below are direct tool setting.

Common tool settings

First select the center of the right end face of the workpiece as the tool calibration point and set it as the zero point after the machine tool returns to the origin, each tool that needs to be used is calibrated with the center of the right end. face of the part as zero point; When the tool touches the right end face, enter Z0 and click the measurement. The measured value will be automatically saved into the tool offset value, which means the tool alignment on the Z axis is correct.

Tool setting X is for test cutting. Use the tool to reduce the outer circle of the part. Measure the value of the outer circle to be rotated (for example, X is 20mm) and enter X20. The offset value will automatically save the measured value. The axis is also aligned;

This tool setting method will not change the tool setting value even if the machine tool is turned off and restarted. It can be used to produce the same parts in large quantities for a long time, and there is no need to recalibrate the tool. tool after stopping the lathe.

Debugging Tips

After the parts are programmed and the knife adjusted, test cutting and debugging are necessary to prevent program errors and tool setting errors from causing collisions with the machine.

You should first carry out no-load stroke simulation processing, facing the tool in the machine tool coordinate system and moving the entire workpiece to the right by 2-3 times the total length of the part, then starting the simulation processing. processing is completed, confirm that the program and tool calibration are correct, and then start processing the workpiece. After the first part is processed, first conduct self-inspection to confirm that it is qualified, and then find a full-time job. Inspection. Only after the full-time inspection confirms that it is qualified, the debugging is completed.

Complete parts processing

After the first part is trial cut, the parts will be produced in batches. However, qualifying the first part does not mean that the entire batch of parts will be qualified, because during the processing process the tool will wear out due to wear. different processing materials. If the tool is soft, tool wear will be low. If the processing material is hard, the tool will wear out quickly. Therefore, during the processing process, it is necessary to frequently check and increase and decrease the tool compensation. value timely to ensure the parts are qualified.

Tool wear processes and dulling standards

Let’s take as an example a part already machined

The processing material is K414, and the total processing length is 180mm. Because the material is very hard, the tool wears out very quickly during processing. From starting point to end point, there will be a slight deviation of 10-20mm due to wear. tool wear. It is therefore necessary to artificially add 10 ~20mm to the program, in order to ensure that the parts are qualified.

The basic principles of processing: Rough processing should first remove excess material from the workpiece, and then finish processing. Thermal degeneration should be avoided during processing of the part. There are many possible reasons for vibrations. due to excessive load; it may be the resonance of the machine tool and the workpiece, or it may be the machine tool; Insufficient rigidity can also be caused by tool dullness. We can reduce vibration through the following methods: reduce the amount of cross feed and processing depth, check whether the workpiece is firmly clamped, increase the tool speed and reduce the speed. Reduce the resonance and check if it is necessary to replace the tool with a new one.

Tips for Preventing Machine Tool Collisions

Machine tool collisions will cause serious damage to the precision of the machine tool, and the impact will be different according to different types of machine tools. Generally speaking, the impact will be greater on machine tools that are not very rigid. Therefore, for high-precision CNC lathes, collisions must be eliminated. As long as the operator is careful and masters certain anti-collision methods, collisions can be completely avoided.

The main reasons for collisions:

☑ The diameter and length of the tool are incorrectly entered;

☑ Incorrect entry of part dimensions and other associated geometric dimensions, as well as errors in the initial position of the part;

☑ The workpiece coordinate system of the machine tool is incorrectly adjusted or the zero point of the machine tool is reset during the machining process, and machine tool collisions mainly occur during the rapid movement of the machine tool. machine tool. the most harmful and must be absolutely avoided. Therefore, the operator must pay special attention to the initial phase of the program execution by the machine tool and when the machine tool changes tools. At this time, a program editing error occurs and the tool diameter and length are entered incorrectly. , a collision will easily occur. At the end of the program, if the CNC axis retraction sequence is wrong, a collision may also occur.

In order to avoid the above collision, the operator should give full play to the functions of the five senses when operating the machine tool. Observe for abnormal movements of the machine tool, sparks, unusual noises and sounds, vibration and odor burned. If an anomaly is discovered, the program must be stopped immediately. The machine tool can only continue to work after the machine tool problem is resolved.

In short, mastering CNC machine tool operational skills is a step-by-step process and cannot be achieved overnight. It is based on mastery of basic machine tool operations, basic machining knowledge and basic programming knowledge. CNC machine tool operating skills are not static. This is an organic combination that requires the operator to give full play to his imagination and practical abilities, and it is innovative work.