Four common classifications of CNC lathe processing
2021-09-15

Four common classifications of CNC lathe processing

CNC lathe processing is a high-tech processing method for machining precision hardware parts. At present, there are many types of CNC lathe processing, which can be classified according to a variety of different principles. Let's take a look at the four common classifications of CNC lathe processing.


1. Classification according to process use

(1) General CNC lathe processing

This kind of CNC lathe processing is the same as the traditional general lathe processing, with CNC turning, milling, boring, drilling, grinding machine, and other mechanical processing methods. The processing possibilities of this type of CNC lathe are similar to those of general-purpose machine tools, except that it can process parts with complex shapes.

(2) CNC lathe processing

This type of CNC lathe processing is developed based on the general CNC lathe processing. In the general CNC lathe, it is on the addition of a tool magazine (can accommodate more than 10-100 tools)and automatic tool changing device and constitute a CNC lathe with automatic tool changing device (also known as multi-process CNC lathe or boring and milling machining center, customarily referred to as machining center), which further development of CNC lathe processing to the direction of automation and efficiency.

(3) Multi-coordinate CNC lathe processing

Some parts with complex shapes cannot be processed with a three-coordinate CNC lathe, such as the processing of propellers and curved aircraft parts, etc. It requires a composite movement of more than three coordinates to process the desired shape. As a result, multi-coordinate CNC lathe processing appears, characterized by the number of axes controlled by the CNC device, and the structure of the lathe is more complex. The number of coordinate axes usually depends on the machining process requirements of the machined parts.


2, According to the CNC CNC lathe movement track for classification

(1) point control CNC lathe processing

This type of CNC lathe processing CNC device can only control the lathe moving parts to move accurately from one position to another. Only the coordinate value of the end of the trip is controlled, and no cutting process is carried out during the movement. As for the speed and route of movement between two relevant points, it depends on productivity. The movement between the two relevant points is first fast to approach the new position to have the highest possible productivity based on accurate positioning. Then the speed is reduced by 1-3 steps to slow down to approach the positioning point to ensure its positioning accuracy.

(2) Point-to-point linear control CNC lathe processing.

When processing this type of CNC lathe, it is necessary to control the position between two related points and control the moving speed and route between the two related points. The route is generally composed of straight lines parallel to each axis. The difference between it and the point-controlled CNC lathe processing is that when the moving parts of the lathe move, it can be cut along a coordinate axis (usually cutting along a 45° oblique line, but not along a straight line with any slope). And its auxiliary functions are more than point-controlled CNC lathes. For example, increasing spindle speed control, cycle feed processing, tool selection, and other functions is necessary.

(3) Contour control CNC lathe processing

This kind of CNC lathe processing control device can simultaneously control two or more coordinate axes continuously. When processing, it is necessary to control the starting point and the endpoint and control the speed and position of each point in the entire processing process so that the CNC lathe can process parts with complex shapes that meet the requirements of the drawings. Its auxiliary functions are also relatively complete.


3. Classified according to the control mode of the servo system

(1) Open-loop control CNC lathe processing

In open-loop control, there is no detection feedback device for CNC lathe processing. The signal processor of the numerical control device is one-way, so there is no system stability problem. It is precisely because of the one-way signal flow. It does not check the actual position of the moving parts of the CNC lathe, so the machining accuracy of the CNC lathe is not high, and its accuracy mainly depends on the performance of the servo system. The working process is: the input data is calculated by the numerical control device to distribute the command pulse, and the controlled worktable is moved by the servo mechanism (servo components are often stepping motors).

(2) Closed-loop control CNC lathe processing

Since the open-loop control accuracy cannot meet the requirements of precision CNC lathes and large CNC lathes, it is necessary to detect its actual working position. Therefore, a detection feedback device is added to the open-loop control numerical control lathe. The position of the moving part of the numerical control lathe is detected during processing to match the position required by the numerical control device to achieve high machining accuracy.

(3) Open-loop compensation CNC lathe processing

The characteristics of open-loop control CNC lathe processing and closed-loop control CNC lathe processing can be selectively concentrated to form a mixed control scheme. Large-scale CNC lathe processing requires very high feed speed and return speed, as well as high precision. If only full closed-loop control is used, the transmission chain and worktable of the CNC lathe are all placed in the control link. The factors are very complicated. Although the installation and commissioning have been complicated, there are still many difficulties. To avoid these contradictions, a hybrid control method can be used.


4. Classified by the numerical control device

(1) Hard-line CNC lathe processing (called ordinary CNC, namely NC). The input, interpolation, control, and other functions of this numerical control system are all realized by integrated circuits or discrete components. Generally speaking, different CNC lathes have different control circuits, so the system's versatility is poor. Because it is all composed of hardware, the functions and flexibility are also poor. This type of system was widely used before the 1970s.

(2) Flexible wire numerical control lathe processing (also known as computer numerical control or microcomputer numerical control, CNC or MNC).

This type of system uses medium, large-scale, and very large-scale integrated circuits to form a CNC device, or a microcomputer and a dedicated integrated chip. Its main CNC functions are almost all realized by software. For different CNC lathes, only different software needs to be compiled. It can be realized, and the hardware can be almost universal. Therefore, the flexibility and adaptability are strong, and it is also convenient for mass production. Modularized software and hardware improve the quality and reliability of the system. Therefore, modern CNC lathes all use CNC devices.

Summarize

The four common classifications of CNC lathe processing must be understood when performing CNC lathe processing. Only by understanding the classification of these CNC lathe processing can we better choose the appropriate CNC lathe for processing according to the shape requirements of the processed parts.

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