Shenyang Machine Tool Complete Equipment Co., Ltd. Haas Qingge
The crankshaft is a crucial component in an engine that converts the linear motion of the pistons into rotational motion. As it spins at high speeds, it creates friction between the main journals and the bearing surfaces. To reduce this friction and ensure smooth operation, lubrication oil is essential. The lubrication system delivers oil to the main journal through external supply lines, while the connecting rod journal receives oil via drilled passages from the nearest main journal. This requires precise design of the crankshaft oil holes—typically straight for the main journals and inclined for the connecting rod journals.
Figure 1: Crankshaft machining site
In manufacturing, crankshaft machining often follows a production line approach, where each machine's performance directly affects overall efficiency. Because of the long length of oil holes, the machining of these features is time-consuming and critical. Therefore, manufacturers focus on optimizing the entire production setup to improve productivity and reduce downtime.
Crankshaft Lubricating Oil Hole Machining Methods
The machining of crankshaft oil holes is typically considered deep hole drilling (L/d > 5), especially for oblique oil holes with depths ranging from 15d to 30d. Common techniques include flat drills, twist drills, gun drills, BTA systems, and MQL (Minimum Quantity Lubrication) methods. In China, gun drills and MQL twist drills are widely used, alongside older methods like rocker drill presses with turning fixtures.
Gun Drill
A gun drill consists of a shank, a body, and a cutting head, all welded together. It uses coolant delivered through the shank and includes a V-shaped groove for chip removal. The cutting head is usually made of cemented carbide. While gun drills offer high precision and good surface quality, they require a complex cooling system, which leads to higher costs and environmental concerns. Additionally, they need guide sleeves for support, reducing machining efficiency.
2. MQL Technology
MQL technology involves mixing compressed air with a small amount of lubricating oil to create fine droplets that are sprayed onto the cutting area. This method significantly reduces oil consumption compared to traditional wet machining, minimizes environmental impact, and improves cutting efficiency and tool life.
Figure 2: MQL application
Advantages of MQL include reduced oil usage, improved surface finish, lower energy consumption, and easier maintenance. It also allows for cleaner workpieces and simpler fluid management, making it a sustainable and efficient option for modern manufacturing.
MQL Twist Drill Processing Equipment
Our factory’s SUC8149 series crankshaft oil hole machining CNC machine tool utilizes MQL twist drill technology. This five-axis machine (X, Y, Z, A, B) offers flexibility in processing both straight and oblique oil holes. The machine features a hydraulic chuck, a tailstock center, and a turret mounted on a column slide for multi-level operations. The B-axis rotation enables precise angle adjustments for different oil hole configurations.
Figure 3: MQL twist drill diagram
The SUC8149 machine uses a specialized MQL system that ensures proper oil mist delivery through the spindle. This system includes a rotary joint and inner cooling channels, allowing for efficient lubrication and cooling. Using MQL special expansion cores with end O-ring seals improves sealing performance, ensuring optimal pressure and flow for high-quality machining.
Case Study
Using the Chongqing Xiaokang 474 crankshaft as an example, the SUC8149 machine tool demonstrates excellent performance. The total cutting time for various operations, including drilling and chamfering, was calculated to be approximately 84.82 seconds. This highlights the efficiency of MQL twist drills in deep hole machining.
Conclusion
In summary, MQL twist drill technology offers significant advantages in crankshaft oil hole machining, including high efficiency, reduced environmental impact, and improved surface quality. These benefits have been consistently demonstrated in our factory’s production over the years, making MQL a valuable and sustainable choice for modern manufacturing.
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