The SBS Balance System operates on a principle of mass compensation for a given grinding wheel imbalance. The Intrinsic Imbalance of a grinding wheel is equal to the product of the wheel's mass multiplied by the distance between the wheel's center of mass and the wheel's center of rotation (figure 1).

The imbalance of a grinding wheel is determined in practice by use of the Measured Imbalance of the wheel. The Measured Imbalance is equal to the product of a mass, affixed to the grinding wheel to balance it, multiplied by the distance between that mass's center and the center of rotation of the grinding wheel (figure 2).

In both cases, the imbalance is given in terms of a mass multiplied by a distance, with (grams)(centimeters) being the units utilized for reference by the system.

In order to correct for various and changing imbalances which occur on a user's grinding machine, the SBS Balance System uses two movable weighted masses, which can be independently positioned so that their resulting compensation will counter any imbalance which is within the specifications of the system. These weights are located in the balance head, and are driven by high torque electrical motors through a precision gear train.

Figure 3 is a simplified block diagram of the SBS Balance System. The system consists of the Balance Head, a Balance Head Cable, a Vibration Sensor, and the SBS microprocessor-driven, balance Control Unit. Imbalance is expressed as spindle movement or vibration and is detected from the grinding machine by the sensor in peak to peak units of measure. The vibration signal from the sensor is transmitted to the control unit, which filters the signal by RPM. The control unit then drives the two balance head masses in the direction that reduces the amplitude of the incoming vibration signal.

When the balance weights are positioned so that minimum vibration is achieved, the balance cycle is complete. Figure 4a shows a rotating grinding wheel that is unbalanced, with an SBS Balance System installed. The imbalance is represented by the white dot located on the circumference of the wheel. The other two black dots represent the masses located in the balance head. By incrementally repositioning the weights, a triangulation is achieved which cancels out the imbalance, as shown in Figure 4b.

The SBS Balance System is designed to dynamically correct for grinding wheel imbalance, with its detrimental effects on quality of surface finish, accuracy of shape production, wheel life, and machine bearing life. The system cannot correct for other environmental problems, which may also impact these areas. This section is intended as a discussion of some common environmental problems, which may influence grinding quality and the ability of the SBS Balance System to fully demonstrate its benefits.

Other Sources of Vibration
A most common source of vibration is adjacent machinery. It is therefore important that a grinding machine be properly shock mounted or otherwise isolated if vibration-producing machinery is operating nearby. Another source of vibration may be components mounted on the machine, such as pumps, motors, drives, etc.

The SBS Balance System may not operate as well under the influence of certain external vibrations. The system filters the vibration signal it detects from the grinding machine by the frequency of the spindle RPM. This means that vibrations occurring at other frequencies than that of the rotating wheel will be ignored by the system. In the case of adjacent machinery operating at the same frequency, or in beat with that frequency, the system will be unable to distinguish vibrations occurring from wheel imbalance with those originating in the adjacent machine.

An excellent test for environmental vibration is to monitor the vibration level on the grinding machine while the spindle is not turning. The vibration level should be checked in various locations on the grinding machine, but in particular at the location the vibration sensor is to be mounted. All surrounding equipment, including any auxiliary pumps or attachments on the grinding machine should be operating during this test. The SBS Balance System can quickly let you accomplish this test (see: Background Vibration section). The SBS Balance System can not remove these vibrations.

Machine Condition
The grinding machine's condition is important in determining the balance level, that the SBS Balance System can achieve. The spindle itself should be balanced, as well as all components in the drive train of the spindle (i.e. belts, pulleys, motor, etc.). The balance system can readily determine if any significant imbalance exists in the machine itself. Simply use the same method as described above for checking environmental vibration, except test with the spindle running and with no wheel mounted. The SBS Balance System does not remove these vibrations.

The SBS Balance System is easily installed in a short period of time. This section provides instructions for mounting of the system hardware on the grinding machine. Included are sections pertaining to installing the balance head, making system connections, installing the vibration sensor, and selecting the proper line voltage setting.

External Balance Head/ Adaptors
The Balance Head is mounted with the provided adaptor to the machine spindle (figure 5a). The mounting adaptor is specifically designed to accommodate the particular machine's spindle configuration, and will vary in design. In general, the adaptor will consist of two parts. The Adaptor Nut mounts on the Grinding machine, usually replacing the spindle nut of the machine, either on the wheel or pulley end of the spindle. The Adaptor Flange will bolt to the Balancer, and then thread onto the installed Adaptor Nut. Appropriate wrenches are supplied for both parts. Use of a lubricating compound between the Balance Head and Mounting Adapter is recommended, to ensure ease of future disassembly.

Lock Screws are a feature of many adaptor designs, where required by high machine speeds or machine spindle braking. These lock screws will consist of M6 socket set screws in the face of the Adaptor Nut, and M5 socket set screws in the outer diameter of the Adaptor Flange (figure 5a).

Warning - All lock screws must be properly secured each time the Adaptor Nut or Adaptor Flange is installed in place, in order to prevent the assembly from coming loose during operation of the grinder.

Follow this assembly procedure to ensure proper mounting of Adaptor Nuts and Flanges were lock screws are part of the adaptor design:

1. Loosen all lock screws before assembly. The engagement end of these screws should be below flush with the face of the adaptor part where they exit.
2. Screw the Adaptor nut onto the machine wrench tight, using the supplied wrench. Use of hammers or wrench extension bars are not advised.
3. Tighten all the lock screws in the Adaptor Nut, wrench tight.
4. Thread the Balancer/ adaptor flange assembly onto the mating threads on the Adaptor Nut.
5. Tighten the lock screws in the Adaptor Flange, wrench tight
6. All lock screws must be fully loosened before attempting removal of these parts from the machine.

The Balancer must be checked for machine clearances upon installation. Make sure there is no interference between the Balance Head or adaptor and any part of the machine (workhead, tailstock, etc.), especially with the wheel worn to it's smallest diameter (figure 5b). Modify the machine guarding if needed to provide clearance from the balancer.

The Balance Head Cable should be restrained to prevent the cable from being caught up in the rotating machine (figure 5c), but should allow for the cable’s removal as necessary during wheel changes.

These components are designed for the harshest environments and the most aggressive coolants. However, common sense dictates that where possible, machine guarding should be modified to allow the rotary junction and cable to extend outside the guard. Optimally, the cable should be secured so that the connector on the Balance Head points down, as shown in the diagram. This position will minimize the chance of fluid or swarf entering the connector when the connector is opened during wheel changes. While the connection is opened, if contamination of the cable connector pins occurs, the pin area must be cleaned prior to reassembly. If heavy wheels are being changed, remove the Balance Head from the area during wheel changes. Most adapters for larger machines are of a two piece design, which simplifies this process.

These installation drawings show the standard balancer version, with the SBS slip ring collector (rotary electric junction) design. Another balancer option is available which includes the SBS non-contact collector. When this balancer version is used, the installation is similar, except that the balancer comes in two parts, with the separate collector piece being mounted across an air gap from the balancer, on a stationary part of the machine. Additional mounting instructions will be provided with this version of balancer describing in detail how this is to be accomplished.

Internal Balance Head
Internal Balance Heads are designed for mounting inside or internal to the machine spindle. The machine manufacturer must provide a precision-machined mounting bore as part of the design of the grinder's spindle in order to accept an internal balancer. The method of attachment is the essential difference between an internal balancer and an external balancer. Once installed, the operation of the two designs is identical and they are discussed interchangeably throughout this manual. The mounting diagram (figure 6) shows how the internal balancer is mounted in the wheel end of the machine spindle. The flange style mounting shown is typical, although a taper lock mounting option is available which eliminates the flange mount and allows the whole internal balancer to fit within the diameter of the mounting bore.

The internal balancer shown is cabled to the SBS collector, which is mounted separately at the rear end of the spindle. With other versions of the balancer, the collector can also be mounted at the wheel end of the spindle, directly attached to the balancer, eliminating the need for the cable bore down the center of the spindle. Both the standard SBS slip ring collector, and the SBS non-contact collector, are available options with the internal balancer.

The SBS Control Unit should be mounted in a location that allows observation of the display by the machine operator. Mounting hardware is available for installation on horizontal surfaces or for rack mounting in standard 19" racks. Cabling connections to the control unit include the Vibration Sensor Cable, the Balance Head Cable, the power cord, and CNC Interface Cable if applicable (see: System Connection diagram). All connections are clearly labeled on the rear of the control unit. Be sure that the proper fuses (Two 3 Amp SLO-BLO) are installed. (see: Rear Panel Controls section).

Vibration Sensor Location
The Vibration Sensor can be mounted on the grinding machine either by use of the magnetic mount provided, or by permanent stud mount. The magnetic mount should be used during initial system start up, until a good permanent location is found on the grinding machine for the sensor. The sensor can then be permanently stud mounted at that location. When stud mounting the sensor, a machined flat should be supplied at the mounting location on the machine.

The location and installation of the sensor are crucial to successful operation of the SBS Balance System. Because of differing machine characteristics, Vibration Sensor location is specific to machine model. There are some general principles that should assist in finding a proper sensor location for your grinding machine.

1. The first general principle is to locate the Sensor in the same direction as the centerline between the grinding wheel and the workpiece. The best place to start is a flat machined surface on the spindle housing over the bearing closest to the wheel, and perpendicular to the spindle’s centerline (figure 7a). A vertical mounting surface is preferable on most cylindrical grinding machines because the sensor is in line with the grinding wheel and the workpiece. For this same reason, on surface grinders and creep feed grinders, a horizontal mounting surface is generally best. Although the balancer itself may be mounted either on the wheel or pulley end of the machine, the Sensor should always be aligned at the wheel end of the machine (figure 7b).
   
   
2. The second general principle is to locate the sensor on a rigid part of the machine structure, where vibration from the spindle will be accurately transmitted. On some machines, the wheel guard can be a good location to mount the sensor, if it is heavy enough and rigidly attached to the spindle housing. The balance system relies on vibration signals received from the Vibration Sensor to accurately display the current vibration level, in peak to peak units, and to balance the grinding wheel. The system employs narrow bandwidth filters that prevent vibration at non-spindle frequencies from being detected. However, in applications where the motor or other machine components are running at the same speed or frequency as the spindle, interfering vibrations may result. Careful experimentation with the sensor’s location goes a long way in minimizing sources of interference.