Control mode of measuring device for CNC machine tool 10

1. Classification according to processing technology.

1. CNC machine tools for metal cutting, 2 CNC machine tools for special processing, 3 CNC machine tools for plate processing.

2. Classification according to the control movement trajectory.

1 point control CNC machine 2 linear control CNC machine 3 contour control CNC machine tool.

3. Classification according to the characteristics of the driving device.

1 Open-loop control CNC machine tool 2 Closed-loop control CNC machine tool 3 Semi-closed-loop control CNC machine tool 4 Hybrid control CNC machine tool: (1) Open-loop compensation type. (2) Semi-closed-loop compensation type.

The problem is not specific enough to be able to · Measuring device?? Control mode?? Why do you need a measuring device when the CNC machine itself has a coordinate display?? As long as the knife is right, it's OK...

Direct and indirect measurements.

1 Direct measurement.

Direct measurement is to directly install the detection device on the actuator, such as grating, induction synchronizer, etc. to directly measure the linear displacement of the worktable, and the position detection device is installed on the actuator (i.e., the end piece) to directly measure the linear displacement or angular displacement of the end piece of the actuator, which can constitute a closed-loop feed servo system. Measurement methods include linear grating, linear induction synchronizer, magnetic grating, laser interferometer and other measurement of the linear displacement of the actuator. Because this detection mode is to adopt a linear detection device to measure the linear displacement of the machine tool, therefore, its advantage is to directly reflect the linear displacement of the workbench; The disadvantage is that the detection device is required to be equal in length to the stroke, which is a big limitation for large CNC machine tools.

2 Indirect measurements.

The indirect measuring device is to install the detection device on the ball screw or the shaft of the driving motor, and indirectly measure the linear displacement of the actuator by detecting the angular displacement of the rotating part.

The position detection device is installed on the transmission element or the drive motor shaft in front of the actuator, and its angular displacement is measured, and the linear displacement of the actuator can be obtained after the transmission ratio is converted, so that a closed-loop servo feed system can be formed, such as the pulse encoder is installed on the motor shaft.

Indirect measurement is reliable and convenient to use, and there is no length limit; The disadvantage is that the transmission chain error of linear conversion into rotary motion is added to the detection signal, which affects the measurement accuracy. Generally, it is necessary to compensate for the transmission error of CNC machine tools in order to improve the positioning accuracy.

In addition to the above position detection devices, the servo system often includes speed detection elements to detect and adjust the engine speed. A commonly used element is a tachogenerator.

The position detection device is an important part of the servo system of CNC machine tools. Its function is to detect displacement and velocity, send feedback signals, and form a closed-loop or semi-closed-loop control. The machining accuracy of CNC machine tools is mainly determined by the accuracy of the detection system.

Different types of CNC machines have different requirements for position detection elements, accuracy requirements for inspection systems and maximum movement speed of the measured components. The highest level of detection of components and systems is now the resolution of the detected displacement (the smallest amount of displacement that can be detected) of up to 1 m at a maximum moving speed of 240 m for the measured part, e.g. 24 m min.

The highest resolution is achievable.

CNC machine tools have the following requirements for position detection devices:

1) It is less affected by temperature and humidity, works reliably, can maintain accuracy for a long time, and has strong anti-interference ability.

2) Within the moving range of the machine tool actuators, it can meet the requirements of precision and speed.

3) It is easy to use and maintain, and adapts to the working environment of the machine tool.

4) Low cost.

The numerical control device is the center of the CNC machine tool, which is generally composed of an input device, a memory, a controller, a combinator and an output device in the ordinary CNC machine tool. The numerical control device receives the information of the input medium, and identifies, stores and calculates it, and outputs the corresponding command pulse to drive the servo system, and then controls the action of the machine tool. In the computer numerical control machine tool, because the computer itself contains the above-mentioned units such as combinators and controllers, the role of its numerical control device is completed by a computer.