HEIDENHAIN grating ruler LS487C ML220MM

HEIDENHAIN grating ruler LS487C ML220MM
The essence of measuring displacement with a grating is to use the grating spacing as a standard ruler to measure the alignment and weighing. High resolution grating rulers are generally expensive and difficult to manufacture. In order to improve the system resolution, it is necessary to subdivide the Moir é fringes, and grating scale sensor systems often use electronic subdivision methods. When two gratings overlap at a slight angle, Moir é fringes will be generated in a direction roughly perpendicular to the grating lines, and as the gratings move, the Moir é fringes will also move up and down. This converts the measurement of grating spacing into the measurement of the number of Moir é fringes. Placing four optoelectronic devices at certain intervals within a Moir é stripe width can achieve electronic subdivision and directional detection functions. For example, a grating ruler with a grating line of 50 pairs/mm and a grating pitch of 0.02mm can obtain counting pulses with a resolution of 5 μ m by using four subdivisions, which has achieved high accuracy in industrial measurement and control. Since displacement is a vector, both its magnitude and direction need to be detected, so at least two optical signals with different phases are required. In order to eliminate common mode interference, DC components, and even harmonics, differential amplifiers composed of low drift operational amplifiers are usually used. The four photoelectric signals obtained from four photosensitive devices are respectively sent to the input terminals of two differential amplifiers. The phase difference between the two signals output from the differential amplifiers is π/2. To obtain direction determining and counting pulses, these two signals need to be shaped into square waves with a duty cycle of 1:1. Then, by comparing and discriminating the phase of the square wave, the direction of movement of the grating ruler can be obtained. By counting the square wave pulses, the displacement and velocity of the grating ruler can be obtained.
When installing the grating ruler sensor, it is not allowed to directly install the sensor on rough and uneven machine bodies, let alone on machine bodies that have been painted with primer. The grating ruler and reading head are installed on two components of the machine tool that move relative to each other. Use a micrometer to check the parallelism between the installation surface of the main ruler of the machine tool worktable and the direction of the guide rail movement. The micrometer is fixed on the bed and the worktable is moved to achieve parallelism within 0.1mm/1000mm. If this requirement cannot be met, a grating ruler base needs to be designed and processed. The requirements for the base are as follows: (1) A base with a length equal to that of the grating ruler should be added (the base should be about 50mm longer than the grating ruler). (2) The base is processed through milling and grinding processes to ensure its plane parallelism is within 0.1mm/1000mm. In addition, a reading head base that is the same height as the ruler base needs to be processed. The total error between the base of the reading head and the base of the ruler body shall not exceed ± 0.2mm. During installation, adjust the position of the reading head to achieve a parallelism of about 0.1mm between the reading head and the grating ruler body, and a spacing of about 1-1.5mm between the reading head and the grating ruler body.
HEIDENHAIN grating ruler LS487C ML220MM
After the installation of the grating line displacement sensor is completed, the digital display meter can be connected, the workbench can be moved, and the counting of the digital display meter can be observed to see if it is normal. Select a reference position on the machine tool and move the working point back and forth to the selected position. The reading of the digital display should be the same (or return to zero). In addition, a dial gauge (or dial indicator) can also be used to adjust the dial gauge and digital display to zero simultaneously (or memorize the starting data), and after multiple repetitions, return to the initial position to observe whether the data from the digital display and dial gauge are consistent. Through the above work, the installation of the grating ruler displacement sensor is completed. But for general machine tool processing environments, there are more iron filings, cutting fluids, and oil stains. Therefore, sensors should be equipped with protective covers. The design of the protective cover is determined by enlarging the cross-sectional area of the sensor to leave a certain space size. The protective cover is usually sealed with rubber to provide it with certain waterproof and oil resistant capabilities