Wheel cleaning jet (WCJ) strategy for green grinding: mitigating greenhouse impact in VP50IM steel machining with green silicon carbide wheel

Abstract

Grinding is a machining process used to achieve high geometric accuracy and excellent surface finish for parts in various industries. In this process, a tool called a grinding wheel interacts with the workpiece’s surface, facilitating the removal of material. Due to the lack of defined geometry, multiple cutting edges engage with the material during machining, leading to a significant rise in temperature within the cutting zone. This temperature increase can jeopardize the process, potentially resulting in damage or even the loss of the workpiece. To address these issues, a technique has been developed involving the use of an emulsion comprising oil and water. This fluid is generously applied to the workpiece to provide lubrication and cooling during the machining process. However, the use of cutting oil raises environmental concerns due to its high pollution potential and its adverse effects on the health of machine operators. In this context, the minimum quantity lubrication (MQL) method was introduced, employing a spray nozzle and a compressed air system to directly apply oil to the cutting zone, facilitating lubrication. Nonetheless, this approach revealed limitations in effectively dissipating heat, leading to a phenomenon known as “clogging,” where machining chips adhere to the tool surface, obstructing the abrasive grains. To combat this issue, an auxiliary system was developed to complement MQL. This system directs a compressed air jet at a 30° angle onto the grinding wheel, dislodging the lodged materials from the tool. Hence, the objective of this study was to assess the effectiveness of these lubrication-cooling methods in machining VP50IM steel—a high-hardness material used in mold die manufacturing. For this purpose, the VP50IM ring-shaped workpieces were machined on a CNC cylindrical grinder RUAP515H, under different feed rates (0.25, 0.50, and 0.75 mm/min), using various lubricooling methods (flood, MQL, and MQL + WCJ). After each machining operation, measurements of roughness, roundness error, tool wear, and acoustic emission were conducted. Additionally, G-ratio, cost, and pollution analyses were also carried out to determine the performance for each case. Across various feed rates, the conventional system showed superior efficiency in most cases. However, it also exhibited the highest application cost and associated pollution. In contrast, the MQL + WCJ system emerged as a highly competitive alternative to the flood method, with comparable surface finish and roundness error, along with lower costs and a significantly reduced environmental impact. In terms of feed rates, the 0.25 mm/min feed rate provided the best surface finish for the workpieces; however, this slowness in the process led to an increase in cost and pollutant emissions. On the other hand, the 0.5 mm/min feed rate yielded the most balanced results. Meanwhile, for the 0.75 mm/min feed rate, the disparity between the lubricooling methods became more pronounced.