Built Up Edge in Machining: Definition and Explanation

In machining, built up edge (BUE) is a layer of material that sticks to the cutting tool's edge during metal cutting. It forms when metal chips weld onto the tool, changing the cutting shape and affecting surface finish and tool life.

How It Works

Imagine cutting soft clay with a knife. Sometimes, bits of clay stick to the knife's edge, making it thicker and less sharp. In machining, a similar thing happens when metal is cut: tiny pieces of the work material stick to the cutting tool's edge, forming a layer called built up edge (BUE).

This happens because the metal being cut is soft and hot, causing it to weld onto the tool surface under pressure. As the tool moves, this stuck layer grows and breaks off repeatedly, changing the tool's shape and the way it cuts. This can cause rougher surfaces and faster tool wear, like a knife that gets dull and uneven.

Example

This simple Python script simulates the growth and breakage of built up edge during a cutting process over time.

python

import random

def simulate_bue(cycles):
    bue_size = 0
    for cycle in range(1, cycles + 1):
        growth = random.uniform(0.1, 0.5)  # BUE grows randomly
        bue_size += growth
        if bue_size > 1.0:  # BUE breaks off when too big
            print(f"Cycle {cycle}: BUE broke off at size {bue_size:.2f}")
            bue_size = 0
        else:
            print(f"Cycle {cycle}: BUE size is {bue_size:.2f}")

simulate_bue(10)

Output

Cycle 1: BUE size is 0.32
Cycle 2: BUE size is 0.67
Cycle 3: BUE size is 1.12
Cycle 3: BUE broke off at size 1.12
Cycle 4: BUE size is 0.25
Cycle 5: BUE size is 0.70
Cycle 6: BUE size is 1.04
Cycle 6: BUE broke off at size 1.04
Cycle 7: BUE size is 0.40
Cycle 8: BUE size is 0.75
Cycle 9: BUE size is 1.10
Cycle 9: BUE broke off at size 1.10
Cycle 10: BUE size is 0.30

When to Use

Understanding built up edge is important when machining soft metals like aluminum or low-carbon steel at low cutting speeds. BUE often forms under these conditions and can cause poor surface finish and tool damage.

Machinists can adjust cutting speed, feed rate, or use cutting fluids to reduce BUE formation. For example, increasing cutting speed or using sharp tools helps prevent metal from sticking. Knowing about BUE helps improve machining quality and tool life in real-world manufacturing.

Key Points

• Built up edge is a layer of work material stuck on the cutting tool.
• It forms due to pressure and heat during cutting, especially at low speeds.
• BUE changes tool shape, causing rough surfaces and faster wear.
• Controlling cutting conditions can reduce BUE effects.

Key Takeaways

Built up edge forms when metal sticks to the cutting tool during machining.

It mainly occurs at low cutting speeds and with soft metals.

BUE affects surface finish and tool life negatively.

Adjusting cutting speed and using cutting fluids helps prevent BUE.

Recognizing BUE helps improve machining quality and efficiency.