What is the grinding process for Shanghai ground channel iron?
The error in ground channel iron inspection tools, the precision of customer measurements of ground channel iron, requires the use of an electronic level to complete. Sometimes, when customers use a cast iron straightedge for measurement, the error of the straightedge itself may exaggerate the error of the ground channel iron. The inherent error of the iron plate itself; if the center of the ground channel iron is lower than the surroundings, this is a normal phenomenon. Detailed explanation of rough scraping, fine scraping, and precision scraping of the iron plate: the primary task of rough scraping is to first address the form and position errors. The scraping marks during rough scraping should be wide and carried out boldly.
Scrape each point only once without repeating, with the scraping marks aligned in the same direction and arranged sequentially, changing direction each cycle. Through repeated cycles of continuous scraping, the black spots become denser, transitioning from uneven to even distribution. When any 25mm×25mm area reaches 4 to 6 points, the rough scraping phase is concluded.
Although the precision of ground channel iron is very high, there are requirements for its use. For example, 000-grade ground channel iron must be used in a workshop with constant temperature, dust-free, and vibration-free conditions. Achieving 000 grade is somewhat difficult, as it requires the material of the ground channel iron to have tight organization, with吸水率 (water absorption rate) and hardness also having an impact. For an iron plate to reach 000 grade, there are demands on both the environment and the foundation: the environment must ensure constant temperature and humidity, and the foundation must have sufficient strength and vibration isolation performance. The materials for ground channel iron include high-strength cast iron HT200, HT250, HT300, cast steel, nodular cast iron, etc.

After a cast iron platform wears out from use, it can be re-scraped to restore its precision. Ground channel iron can be inspected for flatness using the coloring method, which is accurate, intuitive, and convenient. Pushing a gauge stand or workpiece on a scraped cast iron platform is smooth without any sticking sensation, facilitating measurement and ensuring accuracy. Marble platforms have a dense organizational structure, smooth and wear-resistant surface, low roughness values, and undergo long-term aging, resulting in complete relief of internal stress. The material is stable, does not deform, is resistant to acid, alkali, and magnetic fields, does not absorb moisture or rust, and is easy to use and maintain. It has a low coefficient of linear expansion and is less affected by temperature. If the working surface is impacted or scratched, it only produces dents without raised patterns or burrs, having no impact on measurement accuracy.
The appearance of ground channel iron is basically box-shaped, made of materials such as HT200-300, QT400-600, using scraping工藝. Manual scraping is an important process in the machining of ground channel iron, determining the flatness error and the number of contact points on the working surface. For grade 0, there should be no fewer than 25 points within a 25mm square area; for grade 1, no fewer than 20 points within a 25mm square area; for grade 2, points within a 25mm square area; for grade 3, no fewer than 12 points within a 25mm square area.
Fine scraping is performed on the basis of rough scraping. The task of fine scraping for ground channel iron mainly addresses surface quality issues, i.e., contact precision, geometric precision (flatness reaching 0.01mm/500mm2), surface roughness (Ra1.6～R), while also taking into account form and position errors. Precision scraping is carried out on the basis of fine scraping. The task of precision scraping is to improve the quality of the scraped surface, taking into account and verifying form and position errors.
Ground channel iron should be made of fine-grained gray cast iron or alloy materials, with a working surface hardness of 170-220HB. Ground channel iron can be divided into three precision grades: grade 0, grade 00, and grade 000. Ordinary ground channel iron is usually grade 0 precision. For example, a 300*300 iron plate with 000-grade precision has an error of 1.5 micrometers, grade 00 has an error of 3 micrometers, making it a measuring tool with relatively high precision.
Weiyue Machinery, Ms. Xie 15350773479