Balancers for Low-Speed Grinders

LORD Corporation’s balancing system for low-speed, high-precision grinders is comprised of five parts: balancer, actuator coil, sensor, controller and software. The balancer is mounted permanently onto the wheel hub and sensors continuously monitor vibration levels while running. When an increase in vibration is detected above a pre-determined level, the controller sends an advisory message to the operator and the machines PLC, either of which can instruct the balancer to make an automatic balance correction.

The balancers have been designed to address the following:

• Grinding wheel wear
• Chatter caused by vibration
• Machine Tool PLC interface

The Balancer

Consisting of no moving parts, the fluid balancer houses four connecting chambers each containing a high-density fluid and heating element. When an imbalance is detected, the controller when initiated activates the on-board microprocessor to direct power to the insert heaters of the heavy chamber. This power vaporizes the high-density fluid, forcing it to the opposite cooler chamber where it condenses into liquid, correcting the unbalance.

Balancing System Features

• Closed loop system, impervious to contamination
• Ability to balance at levels as low as the background noise of the grinder
• No moving parts reduces maintenance
• Rugged construction withstands the harshest environments

The Actuator Coil

The actuator coil has no moving parts. It consists of a stationary primary coil and a rotating secondary coil, which allows power and data to transfer across an air gap between the two coils. The actuator coil also works on oscillating or reciprocating spindles, and will operate at speeds up to 5,000 RPM.

The Controller

The controller continuously monitors vibration levels. When a change occurs which exceed a preset level, the controller determines the optimum balance correction required. Depending upon the mode of operation selected the controller will send an advisory message to the operator and the machines PLC (via either PLC I/O or an RS232 serial port) either of which can instruct the balancer to make an automatic balance correction.

Controller Features

• Data storage (vibration and balance coefficients)
• EEPROM storage of setup parameters
• Automatic self-calibration
• Reduces cycle time
• Improves surface finish and dimensional accuracy
• Extends wheel and spindle bearing life

The Software

The full-featured graphical user interface software provides the ability to view real-time amplitude and phase information in both numerical and graphical formats. Additionally the software provides the ability to view the fluid transfer operation, keeping you informed as to what is happening within the balancer.

The data history files store information regarding the machine's process and performance including: maximum/minimum vibration levels, balance frequency, wheel changes and machine sensitivity at various spindle speeds.

The software captures machine signature ad spectrum readings, providing valuable frequency response information through the entire spindle operating speed range. This information assists in identifying problems associated with structural components, machine resonance and foundations.

Balancers for High-Speed Grinders

LORD designs balancing systems for high-speed, high-precision grinders. The response of the system enables balancing corrections to be performed in seconds, and can be used on machines with automatic wheel changes.

The balancing system is comprised of five parts: balancer, actuator coil, sensors, controller and software. The balancer is mounted permanently onto the spindle of wheel hub; sensors continuously monitor the vibration levels while running. When an increase in vibration is detected above a pre-determined level, the controller sends an advisory message to the operator and the machine PLC, either of which can instruct the balancer to make an automatic balance correction.

The Balancers have been designed to address the following:

• Grinding wheel wear
• Chatter caused by vibration
• High-speed spindles
• Precision two – plane balancing
• Machine Tool PLC interface
• Reduced cycle times
• Improved surface finish and dimensional accuracy
• Extended wheel and spindle bearing life

The Balancer

The electro-mechanical balancer contains a balance ring, which mounts directly onto the spindle shaft or wheel hub. Inside the balance ring are two symmetrical counterweighted rotor assemblies which, when directed, move to create a net correction vector that will offset the measured unbalance. The counterweighted rotors are held in place using permanent magnets that are fixed to the rotors. These magnets create a holding torque, which prevents the rotors from slipping during normal operation, ramp-up or coast down. When a balance correction is required, actuator coil power pulses are sent to magnetically step the rotors to the desired position in a few seconds.

Balancing System Features

• Balances at spindle speeds up to 40,000 RPM
• Balances to levels below G-1.0 at speed prior to grinding or truing
• Balances the entire spindle assembly in seconds after each wheel change
• Protects spindles by monitoring vibration continuously and shutting down automatically if vibration is excessive
• Rugged construction withstands the harshest environment

The Actuator Coil

The actuator coil typically mounts to the wheel guard door. With no moving parts, the actuator coil pulses power to the balancer assembly. The counterweighted rotors are thus moved to the desired counter-balance position. The actuator coils contains sensors for monitoring spindle RPM as well as the angular location of each counterweighted rotor.

The Controller

The controller continuously monitors vibration levels. When a change occurs which exceed a preset level, the controller determines the optimum balance correction required. Depending upon the mode of operation selected the controller will send an advisory message to the operator and the machines PLC (via either PLC I/O or an RS232 serial port) either of which can instruct the balancer to make an automatic balance correction.

The Software

The full-featured graphical user interface software provides the ability to view real-time amplitude and phase information in both numerical and graphical format. Additionally the software provides the ability to view the balancer correction vector, which provides valuable information regarding the available correction capacity.

The ability to remotely access the software via Ethernet and configure the balancer while initiating the balance correction is a popular feature of the software package.