Application of CNC machine tools

Characteristics of CNC machine tools:

Compared with traditional machine tools, CNC machine tools have the following characteristics.

1) High flexibility

Machining parts on CNC machine tools mainly depends on the processing sequence. Unlike ordinary machine tools, it does not need to manufacture and replace many molds and fixtures, and does not need to readjust the machine tools frequently. Therefore, CNC machine tools are suitable for places where the processed parts are frequently replaced, that is, they are suitable for the production of single pieces and small batches of products and the development of new products, thereby shortening the production preparation cycle and saving a large amount of process equipment costs.

2) High processing accuracy

The processing accuracy of CNC machine tools can generally reach 0.05-0.1MM. CNC machine tools are controlled in the form of digital signals. For every pulse signal output by the CNC device, the moving parts of the machine tool move a pulse equivalent (generally 0.001MM), and the reverse clearance of the machine tool feed transmission chain and the average error of the lead screw pitch can be compensated by the CNC device. Therefore, the positioning accuracy of CNC machine tools is relatively high.

3) Stable and reliable processing quality

When processing the same batch of parts, on the same machine tool, under the same processing conditions, using the same tool and processing sequence, the tool path is completely the same, the parts are consistent and the quality is stable.

4) High consumption rate

CNC machine tools can effectively reduce the processing time and auxiliary time of parts. The spindle speed and feed rate of CNC machine tools are large, and CNC machine tools can perform powerful cutting with large cutting volume. CNC machine tools are currently entering the era of high-speed processing. The rapid movement and positioning of the moving parts of CNC machine tools and high-speed cutting processing have greatly increased the consumption rate. In addition, in conjunction with the tool magazine of the machining center, multiple processes can be continuously processed on one machine tool, which reduces the inter-process turnover time of semi-finished products and increases the consumption rate.

5) Improved rest conditions

Before processing, the CNC machine tool is adjusted, the sequence is output and started, and the machine tool can automatically and continuously process until the processing is completed. The operator only needs to do tasks such as sequence output, editing, parts loading and unloading, tool preparation, observation of processing conditions, and parts testing. The labor intensity is greatly reduced, and the machine operator’s work tends to be intellectual work, which is both clean and safe.

6) Standardization and modernization

The processing of CNC machine tools can accurately predict the processing time in advance, and the tools and fixtures used can be standardized and modernized. It is easy to realize the standardization of processing information. At present, it has been organically combined with computer-aided design and manufacturing (CAD/CAM) and is the basis of modern integrated manufacturing technology.

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CNC system of CNC machine tools

1) High speed

The CNC system adopts a microprocessor of more than 32 bits, so that the output, decoding, summing, and output of the CNC system can be realized at high speed, and the resolution of the CNC system can be improved and high-speed and high-precision processing of continuous small sequence segments can be realized.

The new CNC system currently under development with a 64-bit central processing unit (CPU) has enhanced interpolation and fast feed functions, realized high-speed machining, and realized multi-axis control functions. The number of axes controlled is 3-15 in general, up to 24 axes, and the number of axes controlled at the same time can reach 3-6 axes.

2) Multi-function

The CNC system has a variety of monitoring, detection and compensation functions. Such as tool wear detection, system accuracy and thermal change detection, etc., it also has tool life management, tool length offset, tool radius compensation, tool tip compensation, pitch compensation and other functions. Most modern CNC machine tools use CRT display, which can display the trajectory of two-dimensional graphics, and some can also realize three-dimensional black static graphics display. With the help of CRT, the keyboard can realize the functions of sequence output, editing, modification and deletion. Modern CNC systems have hardware, software and fault self-diagnosis functions.

3) Intelligence

In modern CNC systems, adaptive control technology has been introduced. Adaptive control technology is a technology that can adjust the task status characteristics measured during the processing process and enable the cutting process to reach and maintain the best state.

The development of modern CNC system intelligence is currently mainly reflected in the following aspects:

① Automatic detection and automatic centering of workpieces.

② Tool damage detection and automatic replacement of spare tools.

③ Tool life and tool storage status management.

④ Load monitoring, data management, and maintenance management.

⑤ Use feedforward control to compensate vectors in real time.

⑥ The function of real-time compensation of ball rods and other expansions based on thermal deformation during processing.