Chip Breakers for CBN Inserts: Enhancing Efficiency in Machining

In the realm of precision machining, the integration of chip breakers into Cubic Boron Nitride (CBN) inserts has revolutionized the processing of hard materials. This article delves into the concept of chip breakers, their significance, and the advantages they confer when combined with CBN inserts, particularly in the efficient processing of challenging workpieces.

In the field of metal processing, the CBN tools has become the preferred tool for processing hardened steel, cast iron and other hard materials because of its ultra-high hardness and high temperature resistance. However, with the diversity of processed materials and different processing conditions, we received customers' demands: they hope that the Moresuperhard’s CBN inserts can solve the problem of iron filings entanglement during processing, resulting in reduced efficiency and even damage to the workpiece.

Why are CBN inserts easily wound by iron filings?

Material characteristics: The CBN inserts is suitable for high-speed cutting, and the temperature of the iron filings produced during processing is very high (up to 800°C or more). At high temperature, iron filings soften, toughness increases, and it is easy to form long and continuous ribbon chips.

Insufficient chip discharge space: some CBN inserts are designed with flat cutting edges without chip breaker. Chips cannot be broken in time and accumulate in the processing area to form winding.

Effect of cutting parameters: When the feed rate is too small or the cutting depth is not enough, the chip thickness becomes thinner and it is easier to adhere to the tool surface

Understanding hip Breakers

A chip beaker is a specific design feature incorporated into cutting tools, positioned just behind the cutting edge. Its primary function is to manage and control the formation of chips—small fragments of material removed during the cutting process. By influencing the curvature and breakage of these chips, chip breakers prevent the formation of long, continuous chips that can pose safety hazards, damage the workpiece, or interfere with the machining process.

The Role of Chip Breakers in Machining

During machining, especially with ductile materials, the removal of material results in the formation of chips. Without proper control, these chips can become elongated and entangled, leading to several issues:

• Safety Hazards: Long, sharp chips can cause injuries to operators and damage to machinery.

• Surface Damage: Uncontrolled chips can scratch or mar the surface of the workpiece, compromising its quality.

• Operational Interruptions: Accumulation of chips can clog machinery, leading to downtime and increased maintenance.

By incorporating a chip breaker, the cutting tool induces the chips to curl and fracture into smaller, more manageable pieces, mitigating these potential problems.

Cubic Boron Nitride (CBN) Inserts: 

CBN inserts are cutting tools made from cubic boron nitride, a material second only to diamond in hardness. They are particularly effective in machining hard, ferrous materials such as hardened steels and cast irons. The inherent properties of CBN provide several advantages:

• High Hardness and Wear Resistance: Ensures prolonged tool life even under high-speed cutting conditions.

• Thermal Stability: Maintains hardness at elevated temperatures, allowing for dry machining and reducing the need for coolants.

• Chemical Inertness: Resistant to chemical reactions with ferrous materials, preventing tool degradation.

Advantages of Integrating Chip Breakers into CBN Inserts

The fusion of chip breaker designs with CBN inserts amplifies the benefits of both technologies, leading to enhanced machining performance:

Improved Chip Control

The primary advantage of adding chip breakers to CBN inserts is the effective management of chip formation. This control leads to shorter, curled chips that are easily evacuated from the cutting zone, preventing entanglement and ensuring a smoother machining process.

1. Enhanced Surface Finish

Proper chip management minimizes the risk of chips dragging across the workpiece surface, resulting in a superior finish. For instance, the implementation of precision-ground chip breakers has been shown to achieve surface roughness values as low as Ra 0.3μm, indicative of a mirror-like finish.

2. Extended Tool Life

Efficient chip evacuation reduces heat buildup and mechanical stresses on the cutting edge, leading to longer tool life. Some studies have reported a 15% increase in tool longevity when using CBN inserts with chip breakers.

3. Increased Machining Efficiency

With better chip control, machining processes can operate at higher speeds and feed rates without compromising quality. This enhancement can lead to a 20% to 30% increase in processing efficiency.

4. Reduced Machine Downtime

By preventing chip accumulation and potential blockages, the use of chip breakers decreases the frequency of machine stoppages for cleaning and maintenance, thereby improving overall productivity.

5. Versatility Across Materials

While CBN inserts are primarily used for hard ferrous materials, the addition of chip breakers expands their applicability to a broader range of workpiece materials, including those that are prone to producing long, continuous chips.

Case 1: Automobile engine cylinder block processing

When an auto parts manufacturer uses a CBN tool without chip-breaker to process a cast iron cylinder, the problem of iron filings winding frequently occurs, resulting in the need to stop cleaning chips every 30 minutes of processing, which seriously affects the efficiency. Solution: After switching to the CBN tool with chip breaker, the iron chips automatically break into a short spiral shape, the continuous processing time is extended to 2 hours, and the production efficiency is increased by 40%.

Case 2: Hardening of gear shaft

In a gear factory, when finishing quenched steel gear shaft (HRC 60), the workpiece surface was scratched by iron filings, and the scrap rate was as high as 8%. Solution: With a CBN inserts with a precision chute, the iron filings fall off as small fragments, the surface roughness is reduced from Ra1.6μm to Ra0.3μm, and the scrap rate is reduced to 0.5%.

Case 3: Intermittent cutting of aerospace titanium alloys

When machining titanium alloy structural parts in an aviation parts factory, the long iron filings winding tool causes vibration, resulting in tool breakage. Solution: Custom corrugated chest-breaking groove CBN tool to force chip breakage through periodic pressure fluctuations, increasing tool life from 50 to 200 pieces.

Select a grinding CBN inserts with chip breaker and you will get:

The processing efficiency is increased by 20%-30%；

Tool life is extended by more than 15%；

The workpiece surface roughness is reduced to Ra0.4μm or less；

Whether cutting cast iron intermittently or finishing quenched steel, grinding CBN inserts with chest-breaker is your secret weapon to improve your competitiveness. Contact us for a customized solution!

---EDITOR: Doris Hu, Erin Zhang

---POST: Doris Hu