1. Introduction to Sensors
A sensor is a device or device that can sense a specified measured quantity and convert it into usable output signals according to a certain pattern. Its input signal (measured) is often non electrical quantity, while the output signal is often easily processed electrical quantity, such as voltage.
There are many types of sensors, with different classification standards and nomenclature. Common ones include resistance sensors, inductive sensors, capacitive sensors, temperature sensors, piezoelectric sensors, Hall sensors, thermocouple sensors, photoelectric sensors, digital position sensors, etc. The sensors used in CNC gantry drilling and milling machines mainly include photoelectric encoders, linear gratings, proximity switches, temperature sensors, Hall sensors, current sensors, voltage sensors, pressure sensors, liquid level sensors, rotary transformers, inductosyn, speed sensors, etc. They are mainly used to detect position, linear displacement and angular displacement, speed, pressure, temperature, etc.
2. The demand for sensors in CNC gantry drilling and milling machines
Due to the characteristics of high precision, high speed, and safety and reliability, CNC gantry drilling and milling machines are rapidly becoming popular in manufacturing technology and equipment updates. CNC gantry drilling and milling machine is an automated machine tool equipped with a program control system, which can make the machine move and process parts based on the programmed program. It integrates new technologies such as machinery, automation, computer, measurement, and microelectronics, and uses various sensors. This article introduces the application of various sensors in CNC gantry drilling and milling machines.
3. Displacement detection
The sensors for displacement detection mainly include pulse encoders, linear gratings, rotary transformers, induction synchronizers, etc.
3.1 Application of Pulse Encoder
Pulse encoder is an angular displacement (speed) sensor that can convert mechanical rotation angles into electrical pulses. Pulse encoders can be divided into three types: photoelectric, contact, and electromagnetic, among which photoelectric is more commonly used.
In Figure 1, the X-axis and Z-axis ends are respectively equipped with photoelectric encoders for angular displacement measurement and digital velocity measurement. The angular displacement can indirectly reflect the linear displacement of the drag plate or tool holder through the screw pitch of the lead screw.
3.2 Application of Linear Grating
Linear grating is made by utilizing the transmission and reflection phenomena of light, and is commonly used for displacement measurement. It has high resolution and measurement accuracy compared to photoelectric encoders, making it suitable for dynamic measurement.
In the feed drive, the grating ruler is fixed on the bed, and the pulse signal generated directly reflects the actual position of the drag plate. The servo system for detecting the position of the workbench using a grating is a fully closed-loop control system.
3.3 Application of Rotating Transformers
The resolver is an induction micromotor whose output voltage is a Continuous function of angular displacement. A rotary transformer consists of a stator and a rotor. Specifically, it consists of an iron core, two stator windings, and two rotor windings. The primary and secondary windings are placed on the stator and rotor respectively, and the degree of electromagnetic coupling between the primary and secondary windings is related to the rotation angle of the rotor.
3.4 Application of inductosyn
Inductosyn is made using the principle that the mutual inductance of two planar windings varies with different positions. Its function is to convert angle or linear displacement into the phase or amplitude of induced electromotive force, which can be used to measure linear or angular displacement. According to its structure, it can be divided into two types: linear and rotary. The linear induction synchronizer consists of two parts: a fixed length and a sliding ruler. The fixed length is installed on the machine bed, and the sliding ruler is installed on the moving parts and moves with the workbench; The stator of a rotary inductosyn is a fixed disk, and the rotor is a rotating disk. Inductosyn has advantages such as high accuracy and resolution, strong anti-interference ability, long service life, simple maintenance, long-distance displacement measurement, good processability, and low cost. Linear inductosyn is currently widely used in large displacement static and dynamic measurements, such as in coordinate measuring machines, CNC gantry drilling and milling machines, high-precision heavy-duty machine tools, and machining center measurement devices. Rotary inductosyn is widely used in turntables of machine tools and instruments, as well as in various rotary servo control systems.
4. Requirements for sensors for CNC gantry drilling and milling machines
High reliability and strong anti-interference; Meet the requirements of accuracy and speed; Easy to use and maintain, suitable for machine tool operating environment; Low cost.
Different types of CNC gantry drilling and milling machines also have different requirements for sensors. Generally speaking, large machine tools require high speed response, while medium and high-precision CNC gantry drilling and milling machines mainly require accuracy.
The above introduces the application of sensors in CNC gantry drilling and milling machines. With the upgrading of sensor technology, CNC gantry drilling and milling machines will inevitably enter a new height.
