A New Era in Superhard Material Grinding: Analysis of the Advantages of Using Ceramic CBN Grinding Wheels in Centerless Grinding Machines

1. Technical Characteristics of Ceramic CBN Grinding Wheel Centerless Grinding Machines

Core Technical Features of Vitrified CBN Grinding Wheels

Ultra-High Hardness and Wear Resistance

CBN's hardness is second only to diamond (microhardness HV 4000-5000) and far higher than ordinary corundum (HV 2000-2200). It can efficiently grind superhard materials such as hardened steel (HRC 60 and above), cemented carbide, and ceramics, with a wear rate that is only 1/5-1/10 that of corundum grinding wheels.

 

Excellent Thermal Stability

Vitrified bond CBN grinding wheels maintain stable performance below 1000°C. Their coefficient of thermal expansion (3.5×10⁻⁶/°C) is much lower than that of metal bonds, minimizing thermal deformation during grinding and preventing workpiece burns.

 

Self-Sharpening and Controllable Microstructure

The vitrified bond forms a porous structure through high-temperature sintering, allowing the abrasive grains to detach easily after passivation, maintaining their sharpness. By adjusting the porosity (5%-30%) and the bond formula (such as Al₂O₃-SiO₂), the grinding wheel's hardness and chip holding capacity can be customized.

 

High Shape Retention

Traditional grinding wheels are prone to profile wear during grinding, while vitrified CBN grinding wheels offer over three times better shape retention, making them particularly suitable for high-precision centerless grinding (e.g., bearing roller roundness ≤ 1μm).

Technical Advantages of Vitrified CBN Grinding Wheels for Centerless Grinding Machines

Significantly Improved Processing Efficiency

Grinding Ratio (G-value): CBN grinding wheels can achieve 2000-5000 (compared to 100-300 for corundum grinding wheels), increasing material removal rates by 3-5 times.

Linear Speed: Supports high-speed grinding of 80-120 m/s (compared to 60 m/s for conventional grinding wheels), reducing single-piece processing time.

 

Improved Surface Quality and Precision

Roughness (Ra): Fine grinding can reach 0.1-0.2μm, superior to the 0.4μm achieved with a corundum grinding wheel.

Dimensional Consistency: Mass production tolerances can be controlled within ±2μm.

 

Reduced Overall Cost

Although CBN grinding wheels are more expensive per unit, they offer a lifespan of 6-12 months (compared to only 1-2 weeks for corundum grinding wheels), reducing the need for wheel changes by 90% and overall costs by 30%-50%.

 

Typical Application Cases

Case 1: Mass Grinding of Bearing Rollers

Material: GCr15 bearing steel (HRC 62)

Grinding Wheel: Ceramic CBN #180, 100% Concentration

Result: Roundness ≤ 0.8μm, Ra 0.15μm, and a 2-fold increase in daily output

Case 2: Carbide Tool Shaft Grinding

Challenge: Conventional grinding wheel life of only 4 hours

Solution: Switching to a ceramic CBN #320 grinding wheel

Result: Life extended to 120 hours, and tool straightness reached 0.005mm

2. Working Principle of Ceramic CBN Grinding Wheel Centerless Grinding Machines

System Structure and Basic Layout

Ceramic CBN Grinding Wheel Centerless Grinding Machines consist of three core components:

Grinding Wheel: A vitrified bonded CBN grinding wheel (400-600mm diameter) responsible for the main grinding motion

Guide Wheel: A rubber or resin bonded grinding wheel (200-300mm diameter) tilted 1-5° to rotate and feed the workpiece

Workpiece Support: Consists of a front guide plate, a rear guide plate, and a support plate. Forming a stable V-shaped support system

 

Typical layout parameters:

Grinding wheel linear speed: 45-60 m/s (corresponding to a rotational speed of 1500-2500 rpm)

Guide wheel speed: 20-50 rpm (infinitely adjustable)

Workpiece center height: 15%-25% of the workpiece diameter

Grinding Kinematics

Main motion system:

Clockwise rotation of a ceramic CBN grinding wheel. Driven by a variable frequency motor, the speed accuracy is controlled within ±0.5%.

 

Feed motion system:

Guide wheel axis tilt angle α (usually 1-5°).

Guide wheel surface speed decomposed into:

Circumferential component: Vwork = Vguide × cosα (rotating the workpiece)

Axial component: Vfeed = Vguide × Sinα (propels the workpiece axially)

 

Workpiece Rounding Mechanism:

The workpiece forms a triangular contact pattern with the grinding wheel and guide wheel.

High-point Priority Grinding Principle: Surface protrusions contact the grinding wheel first and are removed.

Multiple rotations average out errors, ultimately achieving high roundness.

Special Working Mechanism of Vitrified CBN Grinding Wheels

Microscopic Cutting Behavior:

The hardness of the CBN abrasive grain (8000 HV) is much higher than that of the workpiece material (hardened steel, approximately 800 HV).

The cutting thickness of a single abrasive grain is only 0.1-5 μm.

The grinding zone temperature is 150-200°C lower than that of conventional grinding wheels.

 

Self-sharpening Principle:

Moderate wear of the vitrified bond causes the removal of dull abrasive grains. Continuous exposure of new abrasive grains maintains sharpness.

The special pore structure (15-35% porosity) ensures sufficient chip space.

 

Dimensional Accuracy Control:

Extremely low grinding wheel wear (0.1-0.3 μm/piece).

Automatic compensation system adjusts feed based on online measurement feedback.

 

High-speed stability

Permitted linear speeds of 80-120 m/s (conventional corundum grinding wheels ≤ 60 m/s)

The high rigidity of the vitrified bond suppresses high-speed centrifugal deformation (expansion coefficient 3.5 × 10⁻⁶/°C)

 

Precision retention mechanism

Diameter wear ≤ 0.003 mm per 10,000 grinding cycles (corundum grinding wheels ≥ 0.02 mm)

Dynamic balance grade must meet G2.5 (ISO 1940 standard)

Typical Application Process Example (Bearing Roller Machining)

Loading: Automatically feeds material from a vibrating plate to a support plate

Rough Grinding: #120 CBN Grinding Wheel, 0.2mm Removal

Fine Grinding: Replace with a #320 Grinding Wheel, 0.01mm Removal

Inspection: Online measuring instrument provides real-time feedback on dimensional errors

Dressing: Diamond roller sharpening every 50 pieces (0.003mm feed).

3. Product Advantages of Ceramic CBN Grinding Wheel Centerless Grinding Machines

• Ultra-Long Service Life

Ceramic CBN grinding wheels demonstrate remarkable durability in centerless grinding machines, boasting a service life 8-12 times that of conventional aluminum oxide grinding wheels. In continuous machining tests of bearing steel components, they consistently produced over 8,000 parts after a single dressing cycle, while conventional grinding wheels typically only lasted around 600 parts before requiring dressing. This exceptional durability translates directly into significant economic benefits: tooling costs per part can be reduced by 40-60%, the frequency of grinding wheel changes can be reduced by over 85%, and auxiliary labor hours associated with wheel replacements can be reduced by up to 70%. A longer service life also means more consistent machining quality, eliminating precision fluctuations caused by grinding wheel wear.

 

• Precise Processing Accuracy

This type of grinding machine sets new industry standards for machining accuracy. In mass production, diameter control accuracy can be maintained within ±1 micron, and roundness can be guaranteed to below 0.5 micron when machining hardened steel workpieces. Surface roughness can easily achieve a mirror finish of Ra 0.1-0.2 microns, with no burn layer on the workpiece surface and retained austenite content kept below 5%. In bearing industry applications, product vibration levels have been reduced by an average of 4 decibels, significantly improving the performance of the final product.

 

• Breakthrough Production Efficiency

Vitrified CBN grinding wheels demonstrate impressive material removal rates. When machining GCr15 bearing steel, the material removal rate can reach 15 cubic millimeters per millimeter per second, a 180% increase over conventional grinding wheels. This improvement reaches 200% when machining high-speed steel, and even as much as 250% for the most challenging nickel-based alloy, 718. In actual production, the cycle time for gear shaft machining has been reduced from 45 seconds to 28 seconds, and the work time per piece for oil pump rotors has been reduced by 55%. This increased efficiency not only shortens delivery cycles but also significantly improves equipment utilization, creating greater production capacity for manufacturers.

 

• Broad Material Adaptability

Centerless grinders with vitrified CBN wheels can handle virtually all high-hardness and difficult-to-machine materials. From hardened steels of 60-65HRC to high-speed steels of 63-67HRC, from carbides of 85-92HRA to various engineering ceramics, they all achieve ideal machining results. In the field of high-temperature alloys, they successfully address the problem of "chip adhesion"; achieve crack-free, high-quality machining of carbides; and maintain excellent surface integrity for materials such as titanium alloy TC4. This broad adaptability allows a single machine to meet the machining needs of a wide variety of materials, greatly enhancing its utility.

 

• Excellent Process Stability

The temperature rise is kept within 2 microns after 8 hours of continuous operation, and the integrated thermal deformation compensation system automatically adjusts to maintain accuracy. The CPK value for critical dimension machining remains stable above 1.67, and in a continuous machining test of 2,000 parts, the diameter variation is only ±1.5 microns. The equipment's operating vibration is less than 0.8 mm/s (in compliance with ISO10816 standards), and its mean trouble-free operating time exceeds 4,000 hours. This stability ensures consistent quality during large-scale continuous production and significantly reduces quality risks.

 

• Environmentally Friendly Processing

In terms of energy consumption, vitrified CBN grinding wheels increase the proportion of effective grinding energy to 35%, while conventional grinding wheels suffer from various additional losses as high as 30%. More importantly, dry grinding is possible for certain materials, reducing coolant usage by 90%, reducing grinding waste by 50%, and lowering operating noise by 8-10 decibels. These environmentally friendly features not only lower production costs but also help companies meet increasingly stringent environmental regulations.

 

• A Perfect Platform for Intelligent Manufacturing

 

The vitrified CBN centerless grinding machine features comprehensive Industry 4.0 interface capabilities, enabling real-time monitoring of key parameters such as grinding power, temperature, and vibration, and connecting to MES systems via the OPC UA standard protocol. Advanced AI algorithms predict and automatically compensate for grinding wheel wear, with an accuracy of ±0.5 microns. The application of digital twin technology has enabled the accuracy of virtual grinding wheel life prediction to exceed 90%. Combined with the process parameter optimization recommendation system, it provides ideal basic equipment for the construction of smart factories.

4. Precautions for Using Ceramic CBN Grinding Wheel Centerless Grinding Machines

Key Points for Grinding Wheel Installation and Commissioning

Precision Dynamic Balancing Requirements:

Two-stage dynamic balancing must be performed before installation: coarse balancing (G6.3), followed by fine balancing (G2.5) after installation.

Residual unbalance should be controlled within 0.5 g·cm, and vibration should be ≤ 0.8 μm at high speeds.

Installation and Positioning Specifications:

Use a dedicated hydraulic nut for installation, applying pressure in three steps to the specified torque (usually 120-150 N·m).

Flange contact surface cleanliness must be Ra 0.4 μm or less, and flatness should be checked using an optical flat lens. (≤0.005mm)

 

Process Parameter Optimization Guidelines

Speed Matching Principles:

The recommended grinding wheel linear speed is 45-60 m/s. Specific adjustments may be made based on the material:

Hardened steel: 50-55 m/s

Carbide: 35-45 m/s

High-temperature alloy: 40-50 m/s

Guide wheel speed and inclination angle matching formula: V_workpiece = V_guide × cosα (α = 1-5°)

 

Cooling System Management Standards

Cutting Fluid Selection Criteria:

Synthetic cutting fluid (pH 8.5-9.5) is recommended.

Extreme pressure additives containing sulfur or chlorine are prohibited (they may corrode ceramic binders).

Filtration accuracy requirement: ≤10 μm. Magnetic and paper tape dual filtration is recommended.

Jet Parameter Settings:

Pressure Range: 3- 5 bar (up to 15 bar with high-pressure jetting)

Flow rate calculation: Q = 0.5 × grinding wheel width (L/min)

Nozzle angle: 15° ± 2° relative to the grinding wheel section

 

Key Controls in the Dressing Process

Diamond Roller Dressing:

Dressing speed ratio: +0.6 to +0.8 (rotating in the same direction)

Feed rate: 0.5-1 μm/rev, divided into two steps: coarse dressing (2-3 μm) and fine dressing (0.5 μm)

Optical dressing rotation speed: 30-50 rpm without feed

Online Dressing Monitoring:

Acoustic emission sensor monitors the dressing process; any sudden change in the AE signal >5 dB triggers an alarm.

Power monitoring: Immediately check the roller status if the dressing power increases by 15%.

 

Special Requirements for Workpiece Clamping

Center Height Calculation:

Empirical formula: h = (0.15-0.25) × d_workpiece

For high-precision machining, the contact angle should be measured using a laser displacement sensor (29°-31° is preferred).

Guide Adjustment Specifications:

Gap between the front guide and guide wheel = 0.5 × workpiece diameter

The rear guide should be retracted 0.02-0.05mm to avoid scratches.

V-angle error of the pallet should be ≤ 0.5°.

 

Special Safety Measures

Protective Device Inspection Checklist:

Grinding wheel cover explosion pressure ≥ 5 bar

Interlock device response time < 50ms

Emergency braking distance ≤ 1.5m (at rated speed)

Personal Protection Requirements:

Splinter-proof goggles must be worn (EN166 standard). Gloves are prohibited when operating adjustment mechanisms.

Hearing protection zones (>85dB) are mandatory.

5. Emergency Solutions for Common Problems with Ceramic CBN Grinding Wheel Centerless Grinding Machines

I. Surface Quality Defect Treatment Solutions

Periodic Chatter Marks (Fish Scale Marks)

Emergency Measures:

Immediately reduce the grinding wheel speed by 10-15%

Increase the coolant flow rate by 30% and check the spray angle

Use a portable dynamic balancer for a quick check (target value ≤ 0.8μm)

 

Surface Burns (Discoloration/Cracks)

Emergency Measures:

Switch to high-pressure coolant mode (increase pressure to 8-10 bar)

Reduce the feed rate by half and reduce the linear speed by 3-5 m/s

Use a "grind-and-pause" intermittent process (grind for 2 seconds, pause for 0.5 seconds)

Advanced Treatment:

Test the grinding wheel hardness (K grade recommended)

Optimize dressing parameters: Increase the number of finishing revolutions To 80-100 revolutions

Check the protruding height of the CBN abrasive grains (should be ≥ 1/3 of the grain diameter).

II. Dimensional Accuracy Out-of-Control Measures

Diameter Drift

Temporary Control:

Enable automatic compensation on the online measurement system (step size 0.2μm)

Lock the temperature compensation parameters (ΔT ≤ ±1°C)

Inspect every 10 pieces and create an SPC control chart

System Adjustment:

Check the guide wheel inclination (calibrated using a laser interferometer, error ≤ 0.005°)

Verify the grinding wheel wear compensation curve (it is recommended to update the compensation every 100 pieces)

Recalibrate the workpiece support stiffness (deformation ≤ 2μm under 50kgf pressure)

 

Roundness Out-of-Tolerance (Oval/Rhombus)

Quick Countermeasures:

Adjust the workpiece center height to within 18-25% of the diameter

Increase the guide wheel dressing frequency (dress every 50 pieces)

Add damping rubber strips (hardness 70-80 Shore A) to the support plate. A)

Complete Solution:

Observe the workpiece rotation trajectory with a stroboscope

Optimize grinding wheel characteristics (adjust porosity to 25-30%)

Check spindle radial runout (≤0.001mm)

III. Process System Abnormal Handling

Abnormal Grinding Wheel Wear

Emergency Intervention:

Immediately stop automatic feed and switch to manual mode

Use a diamond pen for local sharpening (pressure 3-5N)

Switch to a spare grinding wheel parameter set (reduce grit size by one level)

Root Cause Analysis:

Perform grinding force spectrum analysis (normal Fn/Ft = 0.3-0.6)

Check coolant penetration (drip test should be ≤2 seconds)

Assess workpiece material hardness deviation (ΔHRC ≤2)

 

Buildup on the Guide Wheel

On-site Cleaning:

Mechanical cleaning with a copper wire brush (speed ≤10rpm)

Spray with a dedicated cleaning agent Detergent (pH neutral)

Briefly reverse the guide pulley (≤30 seconds)

Preventative Measures:

Install an auxiliary scraper (gap 0.02-0.05mm)

Adjust the guide pulley speed ratio (Vguide/Vsand = 1/100-1/80)

Polish the guide pulley surface weekly with aluminum oxide paste

IV. Equipment Failure Emergency Response

Spindle stall

Operational Procedure:

Use the emergency stop button to cut off power

Check the inverter fault code (F11 overload is common)

Manually crank the motor to check for mechanical resistance

Measure the motor insulation resistance (≥5MΩ)

Recovery Steps:

Phase-by-stage restart (first, idle at low speed for 30 minutes)

Restart the engine (20-40-60% ramp temperature increase)

Perform dynamic accuracy verification (ISO 230-3 standard)

 

Cooling system failure

Interim workaround:

Activate backup mist cooling (pressure 0.3-0.5 MPa)

Use dry ice for localized cooling (distance ≥ 100 mm)

Reduce grinding parameters to safe values (Q'w ≤ 5 mm³/mm·s)

System recovery:

Clean the filter (replace if pressure differential > 0.3 bar)

Check the centrifugal pump impeller clearance (0.1-0.15 mm)

Calibrate the flow sensor (error ≤ ±3%)

V. Special Material Processing Anomalies

Carbide chipping

Process adjustments:

Use a fine-grit grinding wheel (D126 instead of D151)

Use a negative rake angle (γ = -5°)

Add auxiliary supports (add one support point every 50 mm)

Parameter optimization:

Reduce the linear speed to 35-40 m/s

Change the feed rate to 0.003-0.00 5mm/pass

Pre-grind 20-30 pieces of soft material after dressing

 

High-temperature alloy chipping

Emergency plan:

Spray anti-stick coating (graphite-based)

Switch to intermittent grinding mode (on/off ratio 3:1)

Increase axial oscillation (amplitude 0.5-1mm)

Long-term solution:

Use an open-structure grinding wheel (organization number 12-14)

Add minimal quantity lubrication (MQL system)

Pre-cool the workpiece (to 15-20°C)

 

VI. Safety Precautions and Taboos

Absolutely prohibited operations:

• Grinding wheel linear speed exceeding 120% of the rated value
• Running at high speed without dynamic balancing
• Using non-special flanges for mounting

Conditions requiring immediate shutdown:

• Abnormal noise (sudden change in sound pressure level >10dB)
• Distinct bubbles in the coolant
• Three consecutive workpieces are out of tolerance

6. Maintenance and Storage Specifications for Ceramic CBN Grinding Wheel Centerless Grinding Machines

Daily Maintenance and Management

• Cleaning and Maintenance Requirements

A three-stage cleaning process must be performed after daily processing: First, use a dedicated air gun with a pressure of no more than 0.3 MPa to remove grinding debris from the grinding wheel surface, paying special attention to removing residue from the pores. Second, wipe the contact surfaces of the guide wheel and the support plate with a neutral detergent with a pH of 6.5-7.5 to prevent chemical corrosion. Finally, thoroughly clean the coolant tank of deposits, keeping the residual volume to no more than 5 mm. A deep cleaning is required weekly, including removing the protective cover to remove dust from the internal mechanism, using an ultrasonic cleaner to clean small precision components, and inspecting the elastic deformation of each seal.

 

• Critical Component Monitoring

The spindle system must be tested daily for temperature rise, with a maximum allowable temperature rise of 35°C. Measure spindle radial runout weekly using a dial indicator. The standard value should be within 0.002mm. Check the step difference of the grinding wheel flange contact surface monthly. Any difference exceeding 0.005mm must be addressed immediately. Hydraulic nuts must undergo a pressure retention test quarterly, with the pressure decay rate not exceeding 5%.

 

Periodic Maintenance Plan

• Preventive Maintenance Items

Hydraulic system filters must be replaced every 500 operating hours. A filter pressure differential exceeding 0.2 bar will seriously affect system performance. Guideway grease should be replenished every 300 hours, ensuring that the fill level reaches at least 80% of the cavity volume. Coolant concentration should be checked daily with a refractometer to maintain a reasonable concentration range of 4-6%. Electrical cabinet dust removal should be performed monthly to maintain dust thickness below 0.5mm.

 

• Precision Restoration Maintenance

Comprehensive precision restoration maintenance should be performed every six months, including testing the machine tool's geometric accuracy according to ISO standards, testing dynamic stiffness characteristics using the vibration method, and recalibrating the CNC system parameters. These maintenance procedures must be performed in a constant temperature workshop, with ambient temperature fluctuations controlled within ±1°C/hour.

 

CBN Grinding Wheel Storage Specifications

• Storage Environment Control

A dedicated storage cabinet must be installed, maintaining an internal temperature range of 15-25°C with an hourly temperature fluctuation of no more than ±2°C. Relative humidity must be maintained between 40-60% RH, with anti-condensation devices installed. The ambient vibration level in the storage area must be less than 0.5 mm/s (10-500 Hz frequency range) to prevent resonance damage to the grinding wheel's microstructure.

 

• Storage Technical Requirements

Use dedicated vertical storage racks, supported by rubber pads with a hardness of 70 ± 5 Shore A, with support points spaced at least 1/3 the grinding wheel diameter. Maintain an inclination angle of 5-10° during storage to prevent the grinding wheel from rolling. Grinding wheels stored for more than six months must be vacuum-packed with a residual pressure no greater than 10 kPa and a color-changing silica gel desiccant placed in the packaging. The packaging seal must be inspected quarterly.

 

Transportation Precautions

• Packaging and Protection Standards

A four-layer protective packaging structure is used: an inner anti-static polyethylene bag, a 10mm thick bubble cushioning layer in the middle, a 5mm hard ABS plastic outer shell, and a solid wooden transport box. The packaging must be clearly marked with a fragile symbol (maximum impact tolerance 3g), an upward arrow (tilt limit 15°), and a temperature-sensitive label (storage temperature 5-35°C).

 

• Loading and Unloading Procedures

Forklifts are permitted, but the fork length must be at least 2/3 of the package width. Crane lifting must ensure the rope angle is greater than 60°. Rough handling such as rolling and throwing is strictly prohibited. Stacking should not exceed two layers. Maintain stability during transportation and avoid sudden acceleration and braking.

 

Pre-commissioning Inspection Procedures

• Inventory Grinding Wheel Inspection

Inventory grinding wheels must undergo rigorous inspection before commissioning: Use a 10x magnifying glass to inspect for surface cracks and measure the outer diameter to within ±0.5mm. A tap test is performed to verify internal integrity, ensuring a crisp metallic sound. During the static balance test, the weight should not exceed 5g. Dynamic rebalancing is required if the weight exceeds the standard.

 

• Preparation for Installation

Newly used grinding wheels must be allowed to acclimate to the temperature in the workshop for at least 48 hours. A gradient heating method should be used, with the temperature rising no more than 5°C per hour. Before installation, ultrasonic cleaning with isopropyl alcohol for 10 minutes is required, and non-working surfaces should be coated with a special anti-rust oil. During installation, the flange contact surface must meet a cleanliness standard of Ra 0.4μm, and flatness should be checked using an optical flat lens.

 

Maintenance Record System

 

Establish a comprehensive electronic record management system that records basic data such as the time, personnel, and equipment status of each maintenance session, as well as the batch number of replaced parts. The system must include trend analysis capabilities to automatically generate early warning reports for common faults such as bearing wear, grinding wheel imbalance, and hydraulic leaks. Maintenance data must be retained for at least five years, and a full lifecycle traceability record must be established for critical components.

 

Strictly adhering to these maintenance and storage specifications ensures optimal operating conditions for centerless grinders equipped with vitrified CBN wheels, extending the mean time between failures to over 8,000 hours and increasing the lifespan of the grinding wheel by 30-50%. Particularly during the rainy season or periods of significant temperature fluctuations, frequent environmental parameter testing should be performed to prevent humidity and temperature fluctuations from affecting equipment accuracy. Maintenance must be performed by professionally trained technicians using factory-specified consumables and tools to ensure quality maintenance meets standard requirements.

7. FAQs on the Application of Ceramic CBN Grinding Wheels in Centerless Grinding Machines

• What are the advantages of ceramic CBN grinding wheels in centerless grinding machines?

Ceramic CBN (cubic boron nitride) grinding wheels offer significant advantages in high-precision grinding in centerless grinding machines due to their high hardness, high thermal stability, and long life. These advantages include:

High Hardness: CBN's hardness is second only to diamond, making it suitable for machining high-hardness materials such as hardened steel, cemented carbide, and ceramics.

Excellent Thermal Stability: The ceramic bond is resistant to high temperatures, reducing thermal deformation and improving machining accuracy.

Excellent Self-Sharpening: The abrasive grains shed easily after passivation, maintaining sharpness and reducing the risk of burns.

Long Life: Compared to ordinary corundum grinding wheels, their lifespan can be extended by 5-10 times, reducing replacement frequency.

 

• What materials are vitrified CBN grinding wheels suitable for?

Vitrified CBN grinding wheels are primarily used for precision grinding of high-hardness, high-wear-resistant materials, including:

Hardened steel (HRC ≥ 50, such as bearing steel and mold steel); Carbide (such as tungsten steel tools); Ceramics and glass (such as zirconium oxide and silicon carbide); High-temperature alloys (such as nickel-based alloys);

They are not recommended for use on soft materials (such as aluminum and copper) because CBN abrasive grains can easily embed into the soft metal, causing wheel clogging.

 

• How should I choose the grit size, concentration, and bond for vitrified CBN grinding wheels? Grit Size Selection:

Coarse Grinding (Ra 0.8-1.6µm): #80-#120

Semi-Fine Grinding (Ra 0.4-0.8µm): #140-#240

Fine Grinding (Ra <0.4µm): #320 and above

Concentration Selection:

Low Concentration (50%-75%): Suitable for high-precision, low-grinding-force machining

Medium Concentration (100%): General-purpose, balancing efficiency and lifespan

High Concentration (150%-200%): Suitable for heavy-duty grinding, but with a higher cost

Binder Selection:

Vitrified Bond (VIT): General-purpose, suitable for most high-precision grinding applications

Metal Bond (M): Suitable for ultra-hard materials, but with poor self-sharpening properties

Resin Bond (B): Suitable for high surface quality, but with poor heat resistance

 

• How to properly dress a vitrified CBN grinding wheel? Dressing Tools: Diamond dressing pen or diamond roller

Dressing Parameters:

Dressing Feed: 0.002-0.01mm/stroke

Dressing Speed: 0.1-0.3m/s

Coolant: Must be used to prevent overheating during dressing

Dressing Frequency:

Rough Grinding: Dress every 4-8 hours

Fine Grinding: Dress every 2-4 hours

 

• How to Prevent Workpiece Burns When Using Vitrified CBN Grinding Wheels on a Centerless Grinding Machine?

Workpiece burns are usually caused by excessive grinding heat. The following measures can be taken:

Reducing Grinding Speed: Appropriately reduce the grinding wheel speed (e.g., from 80m/s to 60m/s).

Optimizing Coolant: Use a highly lubricating coolant to ensure adequate coverage of the grinding area.

Adjusting Feed: Reduce the amount of each cut (e.g., from 0.02mm to 0.01mm).

Choosing the Appropriate Grinding Wheel Hardness: Too hard a grinding wheel can easily cause burns; a softer vitrified CBN grinding wheel can be used.

 

• What causes and solutions for chatter marks or out-of-roundness on workpieces?

Possible causes:

Unbalanced grinding wheel

Unrounded guide wheel

Incorrect workpiece center height

Improper grinding parameters (e.g., excessive feed rate)

Solution:

Rebalance the grinding wheel to minimize vibration.

Dress the guide wheel to ensure roundness.

Adjust the workpiece center height (usually 0.5-1.5mm above the grinding wheel centerline).

Reduce the feed rate and optimize the grinding parameters.

 

• What are the possible causes and solutions for short vitrified CBN grinding wheel life?

Possible causes:

Improper grinding parameters (e.g., excessive feed rate)

Insufficient cooling leading to thermal damage to the grinding wheel

Improper grinding wheel selection (e.g., too low a concentration)

Workpiece material contains impurities (e.g., carbide with too high a cobalt content)

Improvement measures:

Optimize grinding parameters to avoid overloading.

Ensure sufficient coolant flow (≥20 L/min).

Select a CBN grinding wheel with a higher concentration (e.g., 100% → 150%). Check the workpiece material to avoid impurities that may affect the life of the grinding wheel.

 

• What is the difference between vitrified CBN grinding wheels and conventional corundum grinding wheels?

Comparison Items	Vitrified CBN Grinding Wheel	Ordinary Corundum Grinding Wheel (e.g., White Corundum)
Hardness	Extremely high (second only to diamond)	Relatively low
Applicable Materials	High-hardness materials (hardened steel, carbide)	Ordinary steel, cast iron
Lifespan	5-10 times longer	Relatively short, requires frequent replacement
Grinding Efficiency	High, suitable for precision grinding	Relatively low, suitable for coarse grinding
Cost	High, but excellent overall cost-effectiveness	Relatively low, but requires frequent replacement

• How should vitrified CBN grinding wheels be stored and maintained?

Storage environment: Keep the wheel dry and vibration-free, avoiding extreme high or low temperatures.

Pre-installation inspection: Ensure the wheel is free of cracks and that the inner hole matches the flange.

Post-use cleaning: Use compressed air or a specialized cleaning agent to remove grinding debris and prevent clogging.

• Typical Applications of Vitrified CBN Grinding Wheels on Centerless Grinding Machines

Bearing roller grinding: High precision and consistency, with Ra up to 0.2µm.

Carbide tool grinding: Extend tool life and reduce the risk of burns.

Automotive parts (e.g., camshafts): High-efficiency grinding to improve production efficiency.

8. 10 Key Considerations for Using Ceramic CBN Grinding Wheels in Centerless Grinding Machines

Selecting Appropriate Grinding Wheel Parameters

Grit Size: Choose #80-#120 for coarse grinding and #240-#400 for fine grinding.

Concentration: Generally choose 75%-100%, increasing to 150% for heavy grinding.

Bond: Vitrified bond (VIT) is suitable for most high-precision grinding applications.

Incorrect Selection: Too fine a grit may increase grinding forces, while too high a concentration may increase costs.

 

2. Ensure Grinding Wheel Dynamic Balance

Dynamic balancing is essential before installation to prevent vibration from affecting workpiece surface quality (increasing Ra values).

Inspect regularly, especially during high-speed grinding (linear speeds ≥ 60 m/s).

Impact: Imbalance can cause chatter marks and out-of-tolerance roundness.

 

3. Properly Dress the Grinding Wheel

Dressing Tools: Diamond Dressing Pen or Roller.

Dressing Parameters: Feed 0.002-0.01mm/stroke, Dressing Speed 0.1-0.3m/s.

Cooling: Spray coolant during dressing to prevent heat damage.

Operation Errors: Excessive dressing or excessive speed will accelerate grinding wheel wear.

 

4. Optimize Grinding Parameters

Linear Speed: Recommended for vitrified CBN grinding wheels is 50-80m/s (adjust depending on the material).

Feed Rate: 0.005-0.02mm for fine grinding, and higher for coarse grinding.

Workpiece Speed: Match the guide wheel speed to avoid slippage and deformation.

Typical Problems: Excessive feed can easily cause burns, while too low a speed can lead to poor efficiency.

 

5. Strictly Control Coolant Usage

Flow Rate: ≥20L/min to ensure coverage of the entire grinding area. Filtration: Use a high-precision filtration system (e.g., 5μm or less) to prevent grinding debris from clogging the grinding wheel.

Type: Choose a highly lubricating coolant (e.g., synthetic ester).

Consequences of insufficient cooling: Workpiece burns and thermal cracking of the grinding wheel.

 

6. Adjust the workpiece center height

Recommended value: The workpiece center should be 0.5-1.5mm above the grinding wheel center (adjust based on diameter).

Impact: Too low a height can lead to barreling; too high a height can cause runout.

Testing method: Measure the roundness after a trial grind and fine-tune to the optimal position.

 

7. Avoid grinding soft materials

Applicable materials: Hardened steel, carbide, ceramics, etc. (HRC ≥ 50).

Prohibited materials: Soft metals such as aluminum and copper can easily cause grinding wheel clogging.

Alternative: For soft materials, use corundum or diamond grinding wheels.

 

8. Regularly inspect the guide wheel and support plate

Guide wheel rounding: Out-of-roundness can result in workpiece roundness deviations and requires regular rounding. Support plate wear: Wear requires replacement, otherwise workpiece straightness will be affected.

Maintenance cycle: Check the guide wheel every 8 hours.

 

9. Control grinding allowance

Rough grinding: Allowance per side 0.1-0.3mm.

Fine grinding: Allowance per side ≤ 0.05mm.

Risk of excessive allowance: Increased grinding force and shortened grinding wheel life.

 

10. Standardized operation and safety precautions

Operating standards:

Do not push the workpiece directly by hand; use a dedicated pusher.

Confirm that the protective cover is closed before starting the machine.

Abnormal handling: Immediately stop the machine and inspect any unusual noise or vibration.

Safety red line: Exceeding the grinding wheel linear speed limit may cause a risk of explosion!