Differences Between Conventional Drilling and Spiral Milling Processes
As a new type of hole machining, spiral milling technology has the advantages of smooth cutting process, small cutting force on the tool and one-time machining to meet the accuracy requirements. This technology has become one of the hot spots and difficulties in material processing research at home and abroad. So, what is the difference between traditional drilling and spiral milling process?
Traditional Drilling Process
Traditional drilling processing is mainly characterized by the following:
First, the spindle center of the traditional drilling process has zero linear velocity. This means the drill bit’s center doesn’t participate in cutting. Instead, the downward thrust of the drilling machine squeezes out material from the workpiece. This results in a significant Z-direction force on the tool. When processing titanium alloys and other difficult materials, the tool experiences rapid wear, reducing efficiency.
Secondly, traditional drilling involves continuous cutting, with the knife edge always in contact with the workpiece. This causes high temperatures at the contact surface. Since titanium alloys have poor thermal conductivity, the heat accumulates, accelerating tool wear. Consequently, the processing surface quality declines.
Thirdly, the traditional method of chip removal contributes to tool failure. In drilling, chips are discharged slowly through the drill slots. The cutting heat is mainly carried away by these chips. When heat isn’t evacuated quickly, it accumulates on the workpiece and tool, further accelerating tool wear.
Additionally, chips that come into direct contact with the processed hole’s surface scratch it. This chip removal method negatively affects hole surface quality. In general, traditional drilling cannot meet the precision requirements of aircraft manufacturing. It also requires other processes to ensure hole surface quality. This reduces work efficiency and increases processing costs. Therefore, from both a technical and economic standpoint, traditional drilling is no longer suitable for aircraft manufacturing.
Spiral Milling Process
Compared to traditional drilling, spiral milling adopts a completely different process. The spindle’s “rotation” and its rotation around the hole center create two combined motions. This unique motion provides several advantages.
First, the tool’s trajectory forms a helix instead of a straight line. The tool center no longer coincides with the hole center, resulting in eccentric machining. The tool’s diameter is different from the hole diameter, which breaks traditional drilling limitations. This allows processing of multiple diameter holes with a single tool. Consequently, processing efficiency improves, tool storage reduces, and processing costs lower.
Secondly, spiral milling is an intermittent milling process. This helps tool heat dissipation, reducing wear caused by heat buildup. Additionally, spiral milling greatly improves coolant usage compared to traditional drilling. The entire milling process can use micro-lubrication or even air-cooling, making it a green process.
Thirdly, eccentric machining provides ample space for chip removal. The chip removal method no longer affects hole quality. Therefore, spiral milling technology has significant development potential and strong market prospects. However, as a new process, its mechanism requires further study and exploration.
Advantages of Spiral Milling
(1) Improve the quality of processed holes and tool life.
Relative to the traditional drilling technology, spiral milling significantly improves the quality and strength of the hole; spiral milling hole belongs to the intermittent cutting, lower milling force makes the processing of the hole burr-free; tool diameter is smaller than the hole, the chips can be discharged smoothly, so that the roughness value of the surface of the hole can be significantly reduced; in the processing of composite materials, eliminating the previous traditional punching due to the tip of the blunt tip of the delamination, stripping, low surface quality of the hole and so on. Situation.
Traditional drilling tool center of the cutting capacity is low, and easy to accumulate heat and rapid wear, tool life is generally low; spiral milling holes due to lower milling force so that the tool life significantly improved.
(2) Shorten the development cycle and save the processing cost.
In the manufacture of aircraft or other heavy machinery, the use of spiral milling technology will greatly shorten the development cycle and reduce costs.
The application of spiral milling technology, the same tool can be used to process holes of different diameters and complex shapes. Due to the superiority of the machining method, it is possible to save the traditional work of countersinking taper holes and reaming holes. This means that the number of tool types used for hole machining will continue to decrease in the future. In terms of the entire development cycle, the use of spiral technology can reduce many processes (such as disassembling and disassembling the different holes after the separate burr removal process, reaming, removal of coolant, and then assembling), greatly reducing the processing cycle.
(3) High degree of automation.
To achieve a higher degree of automation is also a way to reduce processing costs. Due to the low milling force of the spiral milling process, this technology can only be applied to industrial robotic devices. Conventional drilling cannot be applied to industrial robotic devices because they are flexible and the axial force of conventional drilling is too high.
(4) Promoting the use of new materials
The use of new materials in aircraft components is an obvious development trend, and new materials such as titanium alloys and composite materials have been widely used. The development and use of new materials need to be supported by suitable processing technology, in the hole processing, research shows that, compared with the traditional drilling technology, spiral milling technology has significant advantages.
Spiral milling process only requires a tool can be processed out of different diameters, high quality holes, not only reduces the time of tool change, but also saves the finishing process, greatly improving work efficiency. In view of the advantages of spiral milling technology, major enterprises, especially in the aviation, mold and die industry, many companies have begun to apply it to the production of practical. With the promotion and application of this technology, the traditional drilling tool will slowly be eliminated, and the new milling device will appear more and more in the machining shop.