Research Progress on Burrs at the Exit of Titanium Alloy Drilling
1. Introduction
With the rapid development of key fields such as medical devices, aerospace, marine surveying, and petrochemical industries in China, there are increasing demands for the material performance of related components. Titanium alloys have gradually become important "strategic metals" in the field of material applications due to their excellent properties such as light weight, high strength, corrosion resistance, and fracture toughness. Titanium alloys are widely used in critical areas such as aircraft engines and fuselage components.
In the assembly and fastening of titanium alloy parts, drilling and milling are essential processes, with drilling occupying a significant portion of the work. However, during the drilling process, due to large axial forces and high temperatures, burrs of different shapes and heights are often formed at the hole exit, which directly affects assembly quality and service performance. Studies show that the burr removal process significantly increases the processing cost of titanium alloys. Therefore, researching the formation mechanism of burrs during titanium alloy drilling and exploring control methods are of great practical significance.
This article reviews the types, formation mechanisms, and control strategies of burrs at the exit of titanium alloy drilling, providing a reference for related research.
2. Types of Burrs at the Exit of Titanium Alloy Drilling
During titanium alloy drilling, the tool interacts with the workpiece to produce shear forces, causing plastic deformation, bending, and tearing of the material. Some of the material is removed, while the remaining portion forms burrs at the hole exit. The shape and size of the exit burrs vary, influenced by cutting parameters and tool geometry. Analyzing the types of burrs helps further study their formation mechanisms.
Studies have shown that burrs formed during titanium alloy drilling can be classified into the following types:
Uniform Burrs: Burrs that form uniformly around the exit.
Uniform Burrs with a Drilling Cap: Burrs with residual material forming a relatively uniform shape.
Crown-like Burrs: Burrs with a crown-like or irregular shape.
Various researchers have found through experiments and simulations that factors such as workpiece stiffness, tool material, and cutting parameters significantly influence burr morphology. Although there is no unified classification standard, the primary types of burrs are the three mentioned above.
3. Formation Mechanisms of Burrs at the Exit of Titanium Alloy Drilling
During the drilling process of titanium alloys, the formation of burrs is closely related to material plastic deformation and the cutting edge of the tool. Research has shown that the formation of burrs at the exit of drilling can be divided into several stages, primarily influenced by cutting forces, temperatures, and tool geometry.
The process of burr formation typically involves the following steps:
During cutting, the material at the bottom of the hole undergoes plastic deformation.
The residual material is pushed towards the hole exit by the drill bit.
When the material exceeds the hole exit edge, it starts to stretch and fracture, eventually forming burrs.
Moreover, through finite element simulations, it has been found that the tool's geometric angle, cutting parameters, and cutting temperature have a significant impact on burr formation. Different cutting parameters and tool structures can lead to the formation of various types of burrs. For example, low feed rates and high spindle speeds generally produce uniform burrs, while high feed rates may result in crown-like burrs.
4. Control Strategies for Burrs at the Exit of Titanium Alloy Drilling
To address burr formation in titanium alloy drilling, researchers have proposed several control strategies, mainly including optimizing cutting parameters, tool design, and machining processes.
4.1 Optimizing Cutting Parameters
The selection of appropriate cutting parameters can help reduce axial forces and cutting temperatures, thereby minimizing burr formation. Studies have shown that optimizing spindle speed, feed rates, and other cutting parameters can effectively reduce burr height. For example, higher spindle speeds and lower feed rates often result in smaller burrs.
4.2 Optimizing Tool Structure
The design of the tool has a significant impact on burr formation. Factors such as tool rake angle, cutting edge length, and tool material all influence burr formation. By optimizing the tool's geometry and selecting suitable materials, burr size and height can be effectively reduced. For instance, using a spiral drill instead of a twist drill can significantly reduce burr size at the exit.
4.3 Optimizing Machining Processes
Traditional drilling processes often lead to burr formation. Researchers have explored new machining methods such as ultrasonic-assisted, rotary ultrasonic-assisted, and cryogenic drilling, which have shown good results. Ultrasonic-assisted drilling can reduce temperatures during the machining process, lowering material ductility and effectively controlling burr size. Additionally, rotary ultrasonic-assisted drilling and cryogenic cooling machining have been proven to significantly reduce burr height.
5. Conclusion
Titanium alloys play a crucial role in various high-end application fields due to their excellent performance. However, controlling burrs during titanium alloy drilling remains a challenge. Existing research shows that by optimizing cutting parameters, tool structure, and machining processes, burr size can be significantly reduced, improving machining efficiency. Future research should further explore the formation mechanisms of burrs, develop new tools and machining technologies, and address the challenges in titanium alloy machining.
