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How to: Balance QRS Type Vibration Tables (SSC-2000 Controllers)
The purpose of this procedure is to explain how to balance the vibration controller parameters of a type QRS vibration system such that each vibration pneumatic channel (Valve Channel) contributes an equal amount of energy to the vibration table or a product mounted on the table.
Perform the following procedure:
1. Mount the feedback accelerometer clusters at locations that will be close to any product fixtures that may be used while remaining clear of possible damage caused by product or fixture loading and unloading. Typical locations would be a couple of inserts in from the left and right edges near the rear of the table.
2. For a table with a product mounted in a fixture, mount a product response accelerometer on the fixture or at a location near the center of the product, on solid structure if available, or near the center of a printed circuit board and perpendicular to its plain.
3. Set the Cycle Time (Vibration Modulation) to 180. Set all Valve Spans to zero except for Valve Channel 1. Set Channel 1 to 100 %.
4. The first part of this procedure finds a minimum acceleration Reference Level that is sufficiently low as not to damage any product, for the mounted product case, but high enough that each vibrator operates smoothly. For the empty table case, monitor the average of the feedback accelerometers and increase the Valve Output Setting until the acceleration reads approximately 3 gRMS.
For the mounted product case, monitor the response accelerometer on the product and increase the Valve Output Setting until the acceleration reads the minimum level required which allows each vibrator to operate smoothly. If, during the following steps, the selected Acceleration Reference Level has to be increased so that all the vibrators operate smoothly, repeat steps 5 and 6 from the beginning at the new level. Record the Final Valve Output Setting (a number between 0 and 200) that achieves the desired acceleration reference level.
5. Record the acceleration achieved by the current output channel.
In this example: Valve Channel #1, Acceleration Reference Level = 3 gRMS, Valve Output Setting = 81.
6. Set the next Valve Channel Span to 100 % and then set the current Valve Channel Span to 0% using the same Valve Output Setting.
7. Repeat steps 5 and 6 until acceleration values are recorded for all Valve Channels.
8. The valve channel that generates the lowest acceleration reading is the “weakest” channel and its Valve Channel Span will then be set to 100%. The second part of the procedure determines the Valve Channel Span settings for each of the other output channels so that each channel contributes an equal amount of energy to the vibration table, or the product mounted in the fixture, as read by the accelerometers.
9. Turn on vibration by again applying the final Valve Output Setting (81 in this example). One at a time, select each Valve Channel Span, except for the weakest channel, and adjust its value (a number between 0 and 100 %) until the acceleration reading is equal to the final selected Reference Acceleration Level (3 gRMS in this example). Record the Valve Channel Number and the Valve Channel Span setting.
10. Return the current Valve Channel Span to 0 and select the next one. Note that the Span setting for the weakest Valve Channel Number should be recorded as 100 %.
11. Repeat steps 9 and 10 until Span values are recorded for all Valve Channels.
12. Enter all the Span values into the controller. Operate the vibration table at a level between 5 and 10 gRMS feedback (or Response), or the level to be applied during a screen, and verify smooth continuous sounding vibrator noise.
This completes the balancing procedure.
For technical assistance contact Screening Services & Training LLC via e-mail. mailto:email@example.com