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Tham khảo tài liệu 'machinery component maintenance and repair part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 310 Machinery Component Maintenance and Repair Correction Mass Figure 6-28. Residual unbalance due to angle error. Table 6-3 Interdependence of Angle and Amount Indication Angle Error Amount Error 1 degree 2 degrees 3 degrees 4 degrees 5 degrees 6 degrees 8 degrees 10 degrees 12 degrees 15 degrees 1.7 3.5 5.2 7.0 8.7 10.5 14.0 17.4 20.9 26.1 Percent of initial unbalance. Listed in Table 6-3 are residual unbalances expressed in percent of initial unbalances which result from applying unbalance correction of proper amount but at various incorrect angular positions. Eventually it was recognized that most balancing machine users are really not so much interested in how accurately the individual parameter is indicated but rather in the accuracy of the combination of all three. In other words the user wants to reduce the initial unbalance to the specified permissible residual unbalance in a minimum number of steps. Acceptance of this line of reasoning resulted in the concept of the Unbalance Reduction Ratio URR for short see definition in Appendix 6A . It expresses the percentage of initial unbalance that one correction step will eliminate. For instance a URR of 95 percent means that an initial unbalance of 100 units may be reduced to a residual unbalance of 5 units in one measuring and correction cycle provided the correction itself is applied without error. A procedure was then developed to verify whether a machine will meet a specified URR. This test is called the Unbalance Balancing of Machinery Components 311 Reduction Test or UR Test. It tests a machine for combined accuracy of amount indication angle indication and plane separation and should be part of every balancing machine acceptance test. Note On single-plane machines the UR test only checks combined accuracy of amount and angle indication. Aside from the UR test acceptance test procedures should also include a check whether the machine can indicate the smallest unbalance specified. For this purpose a test .
