Differences Between Traditional Drilling and Helical Milling Processes
As a new hole machining method, helical milling technology offers the advantages of stable cutting, lower cutting forces on the tool, and the ability to meet precision requirements in a single operation. This technology has become a hot and challenging topic in material processing research both domestically and internationally. So, how do traditional drilling and helical milling processes differ?
1. Traditional Drilling Process
Traditional drilling has the following characteristics:
Firstly, in the conventional drilling process, the spindle center’s linear speed is zero, meaning the drill bit center does not participate in cutting. The material in the center region of the workpiece must be completely removed by the downward thrust of the drill, resulting in a significant Z-axis force on the drill bit. This leads to rapid tool wear and failure, especially when machining hard-to-machine materials like titanium alloys.
Secondly, traditional drilling is a continuous cutting process where the cutting edge is always in contact with the workpiece, leading to high contact temperatures. Titanium alloys have poor thermal conductivity, and the continuous cutting process causes temperature accumulation, accelerating tool wear and failure, and reducing surface quality.
Thirdly, the chip evacuation method in traditional drilling also contributes to tool failure. Chips are evacuated through narrow slots in the drill bit, which is slow, and since most cutting heat is carried away by the chips, inadequate heat dissipation leads to heat accumulation on the workpiece and tool, accelerating tool wear and failure.
Additionally, when chips are in direct contact with the machined hole surface, they can scratch it, affecting the surface quality. Generally, traditional drilling cannot meet the precision requirements of the aerospace industry without additional processes to ensure hole surface quality, reducing efficiency and increasing costs. From a technical and economic perspective, traditional drilling is no longer suitable for the aerospace industry.
2. Helical Milling Process
Compared to traditional drilling, helical milling uses a completely different approach. Helical milling involves the spindle’s “rotation” and “revolution” around the hole center, creating a unique motion pattern that defines its advantages.
Firstly, the tool center follows a helical path rather than a straight line, meaning the tool center does not coincide with the hole center, resulting in an eccentric machining process. The tool diameter differs from the hole diameter, allowing a single tool to machine a series of different diameter holes, breaking the limitation of one tool per hole diameter in traditional drilling. This increases efficiency and significantly reduces the number and variety of tools needed, lowering costs.
Secondly, helical milling is an intermittent cutting process that aids in tool heat dissipation, reducing the risk of tool wear and failure due to temperature accumulation. Importantly, it improves coolant use, allowing for minimal lubrication or even air cooling, making it an environmentally friendly process.
Thirdly, the eccentric machining process provides ample space for chip evacuation, eliminating chip evacuation as a major factor affecting hole quality. This technology has broad development potential and market prospects, though its machining mechanisms require further study.
3. Advantages of Helical Milling
● Improved Hole Quality and Tool Life
Helical milling significantly enhances hole quality and strength compared to traditional drilling. It is an intermittent cutting process with lower cutting forces, resulting in burr-free holes. The tool diameter is smaller than the hole, allowing for smooth chip evacuation and significantly reducing surface roughness. When machining composite materials, it eliminates issues like delamination, peeling, and poor surface quality caused by dull drill tips in traditional drilling.
Traditional drill bits have low cutting efficiency at the center and are prone to rapid wear due to heat accumulation, resulting in shorter tool life. Helical milling, with its lower cutting forces, significantly extends tool life.
● Shortened Development Cycle and Cost Savings
Using helical milling technology in the manufacturing of aircraft or other heavy machinery can significantly shorten the development cycle and reduce costs.
Helical milling can machine different diameter and complex-shaped holes with the same tool, saving the need for countersinking, reaming, and other processes in traditional methods. This reduces the variety and number of tools required.
Throughout the development cycle, helical milling can eliminate many steps (like deburring, reaming, and cleaning coolant after disassembly and reassembly), greatly shortening the machining cycle.
● High Degree of Automation
Achieving higher automation levels is another way to reduce machining costs. Helical milling’s low cutting forces make it suitable for industrial robot applications. Traditional drilling, with its high axial forces, is unsuitable for such applications.
● Promoting New Material Use
Using new materials in aircraft components is a clear trend, with materials like titanium alloys and composites being widely used. The development and use of these materials require suitable machining processes. Research shows that helical milling has significant advantages over traditional drilling for hole machining.
Helical milling can machine high-quality holes of different diameters with a single tool, reducing tool change time and eliminating the need for finishing operations, greatly improving efficiency. Given its advantages, many companies, especially in the aerospace and mold industries, are adopting helical milling in production.
With the promotion and application of this technology, traditional drilling tools will gradually be phased out, and new milling devices will become more common in machining workshops.
