After long-term service in production workshops, cast iron surface plates will suffer a series of precision, structural and surface failures caused by load, temperature, humidity and friction, which seriously affects measurement and calibration accuracy.
Permanent thermal and stress deformation
Cast iron has a higher coefficient of thermal expansion than granite. Long-term exposure to alternating hot and cold workshop environments, continuous heat radiation from machine tools, and uneven local heating create uneven internal thermal stress. Besides, long-term concentrated heavy workpiece stacking generates residual casting stress. Over years, the plate will produce irreversible bending or twisting deformation, leading to excessive flatness error that cannot meet precision inspection standards.
Rust and surface corrosion
Cast iron contains a large amount of iron element. Humid air, cutting fluid, cooling water and oil mist in the workshop will gradually oxidize the working surface. Tiny rust spots expand into large rust pits over time. Rust bulges destroy the reference plane; even after polishing, pitted traces remain, causing jitter and deviation when using measuring tools such as dial gauges and height gauges.
Surface wear, scratches and indentations
Frequent moving, scraping and sliding of steel workpieces, fixtures and cutting tools create countless scratches on the cast iron surface. Heavy parts falling or being placed roughly leave hard indentations. The original uniform wear-resistant layer is damaged, forming uneven surface texture. Gauge components cannot fit closely to the datum surface, resulting in unstable measurement data.
Precision attenuation and datum failure
The cast iron surface plate relies on artificial scraping points to form a precise reference surface. Long-term friction wears down the scraping pattern. The contact uniformity of the datum plane decreases continuously. Even without obvious deformation or rust, the repeated measurement error will gradually increase, failing inspection calibration requirements. Recalibration and re-scraping are required regularly.
Base support settlement and uneven force
Most cast iron plates are placed on adjustable supporting stands. Long-term vibration from workshop equipment loosens the supporting bolts, and the ground foundation slowly settles unevenly. The plate bears asymmetric supporting force, aggravating warpage. Without regular readjustment of support points, the flatness index will quickly exceed the tolerance range.
Oil absorption and dirt accumulation
Cast iron has tiny internal pores. Cutting oil, emulsion and metal powder seep into pores after long use. Stained dirt cannot be completely wiped off with ordinary cleaning methods. The stained layer changes the surface flatness locally and may corrode the interior of the plate, accelerating material aging and precision loss.
Cracks under fatigue load
Repeated impact, long-term overload placement and alternating stress will produce tiny fatigue cracks at the edge or middle of the plate. Microcracks expand slowly under workshop vibration. Once cracks penetrate the plate body, the entire cast iron surface plate loses its use value and cannot be fully repaired.
References
GB/T 7714
Wang C, Liu M. Failure analysis and maintenance strategy of long-service cast iron measuring plate[J]. Manufacturing Technology & Machine Tool, 2019(6):142-146.
MLA
Wang, Chao, and Ming Liu. "Failure Analysis and Maintenance Strategy of Long-Service Cast Iron Measuring Plate." Manufacturing Technology & Machine Tool, vol. 6, 2019, pp. 142-146.
APA 7th
Wang, C., & Liu, M. (2019). Failure analysis and maintenance strategy of long-service cast iron measuring plate. Manufacturing Technology & Machine Tool, 6, 142-146.
