The function and working principle of the grating ruler of machine tool equipment
The grating ruler, also known as the grating ruler displacement sensor, is a measurement feedback device that uses the optical principle of the grating. The grating ruler is often used in the closed-loop servo system of the CNC machine tool, and can be used for the detection of linear displacement or angular displacement. The measured output signal is digital pulse, which has the characteristics of large detection range, high detection accuracy and fast response speed. For example, it is often used in CNC machine tools to detect the coordinates of the tool and the workpiece to observe and track the tool movement error, so as to play a role in compensating the movement error of the tool.
Definition of grating ruler: The grating ruler is a high-precision displacement sensor that digitally expresses the linear displacement through the principle of moiré fringes and photoelectric conversion. The grating linear displacement sensor is mainly used in the linear moving guide mechanism, which can realize the accurate display and automatic control of the movement amount, and is widely used in the digital display of the machining amount of the metal cutting machine tool and the control of the position ring of the CNC machining center. The product has formed a series for various types of machine tools of different specifications, ranging from 50 mm to 30 meters, covering almost all the strokes of metal cutting machine tools.
The grating rulers are classified as follows: 5V, 12V, 15V, 24V square wave, subdivision ruler, sine ruler, there are also positive and negative code signal rulers with strong anti-interference ability specially provided for spark machines, and high power connected to computer numerical control machine tools grating ruler. The structure is divided into two types: wide ruler and narrow ruler. The narrow ruler can be up to 1 meter long, and the wide ruler can be selected within 30 meters. In addition, it can be divided into two types: open type and closed type. Among them, the open type is a high-precision type, and the output waveform is a sine wave. It is mainly used for digital transformation of precision instruments. The highest resolution can reach 0.1um. The closed type is mainly used for the digital transformation of ordinary machine tools and instruments, and the output waveform is square wave. Structure grating scale is composed of scale grating and grating reading head. The scale grating is generally fixed on the movable part of the machine tool, the grating reading head is installed on the fixed part of the machine tool, and the indicating grating is installed in the grating reading head. The figure on the right shows the structure of the grating scale.  Structure of grating detection device The key part of the grating detection device is the grating reading head, which consists of a light source, a converging lens, an indicating grating, a photoelectric element and an adjustment mechanism. There are many structural forms of grating reading heads, which are divided into direct receiving reading heads (or silicon photocell reading heads, mirror reading heads, spectroscopic reading heads, and metal grating reflective reading heads) according to the structural characteristics and application occasions of the reading head. GBC-Q series grating ruler grating ruler definition: The grating ruler is a high-precision displacement sensor that digitally expresses the linear displacement through the principle of moiré fringes and photoelectric conversion. The grating linear displacement sensor is mainly used in the linear moving guide mechanism, which can realize the accurate display and automatic control of the movement amount, and is widely used in the digital display of the machining amount of the metal cutting machine tool and the control of the position ring of the CNC machining center. The product has formed a series for various types of machine tools of different specifications, ranging from 50 mm to 30 meters, covering almost all the strokes of metal cutting machine tools. The grating rulers are classified as follows: 5V, 12V, 15V, 24V square wave, subdivision ruler, sine ruler, there are also positive and negative code signal rulers with strong anti-interference ability specially provided for spark machines, and high power connected to computer numerical control machine tools grating ruler. The structure is divided into two types: wide ruler and narrow ruler. The narrow ruler can be up to 1 meter long, and the wide ruler can be selected within 30 meters. In addition, it can be divided into two types: open type and closed type. Among them, the open type is a high-precision type, and the output waveform is a sine wave. It is mainly used for digital transformation of precision instruments. The highest resolution can reach 0.1um. The closed type is mainly used for the digital transformation of ordinary machine tools and instruments, and the output waveform is square wave.
The main application of grating ruler:
1. Displacement measurement of various measuring mechanisms and instruments: spring testing machine, CMM, projector
2. Digital display system of various machine tools: lathes, milling machines, grinders, boring machines, EDM, drilling machines, etc.
3. Supporting use of various CNC machine tools: CNC milling, machining center, CNC grinding, etc.
4. Matching with PLC, it is used for displacement measurement of various automation mechanisms.
1. The most advanced optical measurement system adopts a reliable and durable high-precision five-bearing system design to ensure the stability of the optical-mechanical system, excellent repeatability and high-level measurement accuracy.
2. The sensor adopts a sealed structure, with reliable performance and convenient installation.
3. It adopts special oil-resistant, corrosion-resistant, high-elasticity and anti-aging plastic waterproof, excellent dustproof and long service life.
4. Specific high level of anti-interference ability, stable and reliable.
5. The light source adopts imported infrared light-emitting diodes, which are small in size and long in life.
6. Using advanced grating production technology, it can produce high-precision grating glass rulers of various specifications
The installation of the linear displacement sensor of the grating ruler is more flexible and can be installed in different parts of the machine tool.
Generally, the main ruler is installed on the worktable (slide board) of the machine tool, and moves with the machine tool, and the reading head is fixed on the bed, so that the reading head is installed below the main ruler as much as possible. The selection of the installation method must pay attention to the splashing direction of chips, cutting fluid and oil. If it must be installed with the reading head facing up due to the limitation of the installation position, an auxiliary sealing device must be added. In addition, in general, the reading head should be installed on the stationary part relative to the machine tool as much as possible. At this time, the output wire is not moved and easy to be fixed, and the ruler body should be installed on the part that moves relative to the machine tool (such as a sliding plate).
1. Mounting base of grating ruler linear displacement sensor
When installing the grating ruler sensor, the sensor cannot be directly installed on the rough and uneven machine body, let alone the machine body with primer coating. The grating main ruler and the reading head are respectively installed on the two parts of the machine tool that move relative to each other. Use a dial indicator to check the parallelism between the main ruler mounting surface of the machine tool table and the direction of the guide rail movement. The dial indicator is fixed on the bed and the worktable is moved, and the parallelism is required to be within 0.1mm/1000mm. If this requirement cannot be met, a grating scale base needs to be designed and processed.
The base requires:
(1) A base that is equal to the length of the grating ruler should be added (preferably the base is about 50mm longer than the grating ruler).
(2) The base is processed through milling and grinding processes to ensure that its plane parallelism is within 0.1mm/1000mm.
In addition, it is necessary to process a reading head base with the same height as the ruler base. The total error between the base of the reading head and the base of the ruler should not exceed ±0.2mm. During installation, adjust the position of the reading head so that the parallelism between the reading head and the scale body is about 0.1mm, and the distance between the reading head and the scale body is about 1~1.5mm.
2. Main ruler installation of grating ruler linear displacement sensor
Use M4 screws on the grating main scale on the worktable installation surface of the machine tool, but do not tighten it, fix the dial indicator on the bed, and move the worktable (the main scale and the worktable move at the same time). Use a dial indicator to measure the parallelism between the plane of the main scale and the direction of movement of the machine guide rail, and adjust the position of the M4 screw of the main scale to make the parallelism of the main scale within 0.1mm/1000mm, and then tighten the M2 screw completely.
When installing the grating main ruler, the following three points should be paid attention to:
(1) When installing the main ruler, if installing gratings over 1.5M, it is not possible to install only the two ends as in the bridge type, and the entire main ruler needs to be supported.
(2) After installing with a base, it is best to use a clip to hold the midpoint (or points) of the ruler.
(3) When the clip cannot be installed, it is best to stick the grating ruler body with glass glue to make the base ruler and the main ruler well fixed.
3. Installation of the reading head of the linear displacement sensor of the grating ruler
When installing the reading head, first ensure that the base surface of the reading head meets the installation requirements, and then install the reading head. The installation method is similar to that of the main ruler. Finally, adjust the reading head to ensure that the parallelism between the reading head and the grating main scale is within 0.1mm, and the gap between the reading head and the main scale is controlled within 1~1.5mm.
4. Limiting device of grating ruler line displacement sensor
After all the grating line displacement sensors are installed, a limit device must be installed on the machine guide rail to prevent the reading head from colliding with both ends of the main ruler when the machine tool moves, thereby damaging the grating ruler. In addition, when purchasing a grating linear displacement sensor, the user should try to choose a grating ruler that exceeds the processing size of the machine tool by about 100mm, so as to leave a margin.
5. Check the grating line displacement sensor After the grating line displacement sensor is installed, you can connect the digital display meter, move the worktable, and observe whether the digital display meter counts normally. Select a reference position on the machine tool, and move the work point back and forth to the selected position. The DRO should read the same (or return to zero). In addition, a dial indicator (or dial indicator) can also be used to adjust the dial indicator and the digital indicator to zero at the same time (or memorize the initial data), return to the initial position after going back and forth several times, and observe the digital indicator and the dial indicator. Whether the data in the table is consistent.
Through the above work, the installation of the linear displacement sensor of the grating ruler is completed. But for the general machine tool processing environment, there are many iron filings, cutting fluid and oil pollution. Therefore, the sensor should be equipped with a protective cover. The design of the protective cover is determined by leaving a certain space size according to the enlarged cross-section of the sensor. The protective cover is usually sealed with rubber to make it have a certain waterproof and oil-proof ability.  Features of milling machine digital display: Automatic centring function, metric/imperial display. Absolute/relative counting conversion function; number storage function in ruler; linear error compensation; hole dividing function on slanted line; circular hole dividing function; circular arc processing function. Bevel machining function. Calculator function, nonlinear error compensation.
1. Technical parameters of digital display meter
1. Voltage range: AC 80V～260V/50Hz～60Hz
2. Power consumption: 25VA
3. Number of coordinates: two coordinates, three coordinates
4. Display: Signed 7-digit display (two-axis or three-axis) data information window adopts eight-digit meter display symbol output
5. Multiplier: 4X
6. Display box allows input signal: TTL square wave
7. Allowed input signal frequency: >100KHz
8. Length resolution 10μm, 5μm, 2μm, 1μm, 0.5μm
9. Operation keyboard: touch the keyboard
10. Grating ruler: the grating pitch is 0.02mm, 0.01mm, the power supply is +5V, and the output two TTL square wave signals with a difference of 90°
2. General/processing functions of digital display:
2: preset number;
3: Metric/Imperial conversion;
4: Absolute/relative coordinate conversion;
5: 200 groups of user coordinates display;
6: Power failure memory;
7: 1/2 value function key display;
8: Linear error correction;
9: sleep shutdown;
10: 200-point auxiliary zero function;
11: Automatically find zero function;
12: calculator function;
13: Circumferential hole;
14: slash hole;
15: Slope processing;
16: Arc processing;
17: Lathe function (optional);
18: Incremental machining of rectangular inner cavity;
19: digital filtering;
20: Radius/diameter display (optional);
21: RS-232-C interface (optional);
22: EDM output etc. can be
Satisfy the use of most machine tools.
1: Counting frequency response is fast and powerful;
2: Die-casting alloy shell, surface electrospray treatment, dust-proof and wear-resistant, good shielding;
3: Professionally designed independent power supply, with wide adaptability, high stability and strong anti-interference ability;
4: High-quality and durable button panel, easy and convenient to replace
5: Function calculation can be performed directly on the digital display, which is convenient for processing.
3. Installation conditions
1. The digital display can work in the environment of 0℃～+40℃. Do not expose to hot sun or high temperature.
2. Keep away from equipment with high voltage, high current and strong magnetic field, and keep the signal cable of the grating ruler away from the power line as much as possible.
3. Avoid metal chips, oil, water, etc. from entering the digital display. Pay attention to dust and moisture; do not install the device on a workbench with large vibration or instability.
4. When the ambient temperature is +40°C, the relative humidity of the air does not exceed 50%. When the temperature is lower, a larger relative humidity is allowed. Special measures should be taken for condensation caused by temperature changes.
3. Installation of combined accessories
Due to the different structure and working environment of various machine tools, there is no unified standard for the installation of sensors. In order to take into account the installation of various machine tools, our company has specially produced various combination accessories for the majority of users to choose from, including sensor housings, installation aluminum strips, digital display Table mounting frame, angle aluminum, mounting aluminum plate, etc.
The digital display is widely used in lathes, milling machines, grinders, wire cutting, radial drills, EDM, boring machines, gantry boring and milling and other types of machining machine tools, which is beneficial to improve processing efficiency and processing accuracy.
1. Application of linear displacement grating sensor The digital display system is mainly used in the measurement of linear moving guide rail mechanism or precision displacement, which can realize high-precision display and automatic control of movement amount, and has been widely used in machine tool processing and precision measurement of instruments. At present, the product has formed a variety of series, complete varieties, exquisite production, precision technology, can be used for digital transformation of various types of machine tools and instruments of different specifications, and can also be specially produced according to the special needs of users. The corresponding digital display system can be used for lathe transformation, milling machine transformation, boring machine transformation, grinding machine transformation, spark machine transformation, drilling machine transformation, wire cutting transformation, coordinate measurement, projection measurement, etc.
1. According to the appearance, there are: 50mm - 3000mm
2. According to the resolution: 1um----5um
3. According to the power supply voltage: 5V----24V
4. According to the output signal, there are TTL square wave, TTL square wave, HTL square wave (5V, 12V, 15V, 24V), RS422 signal, sinusoidal voltage signal 1Vp-p /mm), 0.02mm(50 line pairs/mm), 0.04mm(25 line pairs/mm) Accuracy: ±0.008mm, ±0.01mm, ±0.015mm, (20℃ 1000mm) Reference marks: 25mm interval, 50mm interval , 100mm interval, 200mm interval, or set an absolute position reference point (ABS) at any position of the full scale