Short Answer:
During machining, different types of chips are formed depending on factors like cutting speed, tool material, workpiece material, and machining conditions. The three main types of chips are continuous chips, discontinuous chips, and built-up edge (BUE) chips.
Continuous chips are smooth and formed in ductile materials under proper machining conditions. Discontinuous chips are broken and occur in brittle materials or under high cutting forces. Built-up edge chips form when material sticks to the cutting tool, affecting surface finish. Understanding chip formation helps in improving machining efficiency and tool performance.
Detailed Explanation:
Types of Chips Formed in Machining
In machining processes, chips are formed as the cutting tool removes material from the workpiece. The type of chip produced depends on factors like cutting speed, feed rate, tool geometry, tool material, workpiece material, and the use of cutting fluids. Chip formation affects machining efficiency, tool wear, and surface finish. The three primary types of chips are discussed below.
- Continuous Chips
Continuous chips are smooth and long, formed when machining ductile materials like aluminum, copper, and mild steel. These chips occur under high cutting speeds, sharp cutting tools, and proper lubrication. The continuous nature of the chip allows for a better surface finish and stable machining.
- Characteristics of Continuous Chips:
- Smooth and unbroken flow of material.
- Good surface finish on the workpiece.
- Low cutting force and reduced tool wear.
- Common in high-speed machining of soft metals.
- Factors Affecting Continuous Chip Formation:
- High cutting speed.
- Low feed rate and small depth of cut.
- Sharp cutting tool with positive rake angle.
- Proper use of cutting fluids to reduce friction.
- Discontinuous Chips
Discontinuous chips are broken into small segments and typically form when machining brittle materials like cast iron, brass, and bronze. These chips also occur when machining ductile materials under poor cutting conditions, such as low cutting speed, high feed rate, and improper tool angles.
- Characteristics of Discontinuous Chips:
- Chips break into small pieces.
- Irregular surface finish on the workpiece.
- High cutting forces and tool vibrations.
- Common in machining hard and brittle materials.
- Factors Affecting Discontinuous Chip Formation:
- Low cutting speed.
- High feed rate and large depth of cut.
- Tool with a small or negative rake angle.
- Brittle workpiece material.
- Built-Up Edge (BUE) Chips
Built-up edge chips occur when material from the workpiece sticks to the cutting tool due to high temperature and pressure. This accumulation of material, called a built-up edge, can later break off, affecting the surface finish and causing irregular cuts. BUE formation is common when machining ductile materials like aluminum and low-carbon steel at lower speeds.
- Characteristics of Built-Up Edge Chips:
- Rough and uneven chip flow.
- Poor surface finish due to material sticking to the tool.
- Increased cutting force and tool wear.
- Occurs in ductile materials at lower cutting speeds.
- Factors Affecting Built-Up Edge Chip Formation:
- Low to moderate cutting speeds.
- High feed rate and depth of cut.
- Lack of cutting fluid or improper lubrication.
- Tool material and temperature influence.
Conclusion
Chip formation plays a vital role in machining efficiency and workpiece quality. Continuous chips are ideal for smooth machining, while discontinuous chips often cause rough surfaces and vibrations. Built-up edge chips can lead to tool damage and poor surface finish. Controlling machining parameters like speed, feed rate, tool geometry, and cutting fluids helps in achieving the desired chip formation and improving machining performance