Hydraulic supports are critical components in coal mine operations, ensuring safe and efficient production. As heavy-duty equipment used underground, their performance and durability directly impact both safety and productivity. A key element of the hydraulic support is the hydraulic jack, which enables the movement and control of the support structure. The reliability and flexibility of the entire system depend heavily on the quality of the jack's manufacturing. Poor sealing performance—such as leakage or pressure loss—can lead to serious operational issues, even endangering workers' safety.
The lifespan of a hydraulic support largely depends on the quality of its hydraulic jacks. Among the main components, the piston and piston rod are crucial, especially the sealing grooves that must meet strict surface finish and dimensional accuracy standards. If the surface roughness of the groove bottom is too high, it can cause rapid wear of the sealing elements, leading to leaks, pressure drops, and reduced support effectiveness.
In traditional machining, conventional grooving tools were often used for processing grooves. These tools typically produced surface roughness values between Ra 6.3 to 3.2 μm, which may not be sufficient for precision parts like those found in hydraulic jacks. For example, sealing grooves usually require Ra 3.2 to 1.6 μm with tight tolerances (J s8). This level of precision is difficult to achieve using standard tools due to several limitations.
First, when multiple grooves with different widths need to be machined, aligning multiple tools increases setup time and measurement efforts. Second, wide forming tools can cause excessive radial force, leading to vibration and poor surface finish. Third, using smaller tools to cut grooves can result in chip sticking and tool marks, reducing surface quality. Finally, worn or chipped cutting edges can leave irregularities on the groove bottom, further degrading performance.
To address these issues, an improved concave double-tip grooving tool was developed. This tool modifies the main cutting edge by making it slightly concave, creating two wiper tips and dual cutting edges. This design allows for smoother cutting, reduces vibration, and improves surface finish. It also offers greater versatility, as it can handle various groove widths without frequent tool changes.
This new tool provides several advantages: it’s suitable for batch machining, reduces tool change and setup time, allows for precise control of dimensions, and ensures better surface finish and roundness. Additionally, it minimizes chip sticking and vibration, making it ideal for use on CNC machines. Testing with 260 piston rods showed a significant improvement in efficiency and product quality. The improved tool increased production speed by 2 times, achieved a 100% pass rate, and reduced defects by 30%.
When used with CNC machines, the efficiency could be further boosted, allowing for up to 40 pieces per shift—four times faster than traditional methods. Implementing this tool helped reduce costs, increase profits, and fill a gap in the company’s production capabilities. For example, producing 260 φ80mm piston rods generated a profit of 50,000 yuan, while saving the company 10 million yuan in outsourcing costs.
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