1. Resin Surface no bubble, crack,etc. 2.Dielectric strength:bar-bar 500V/AC, 1S,bar-shaft 3000VAC,60S,no crack or flash 3.Insulation resistance:room temperature,500V/DC Mega meter, insulation resistance> 100MΩ 4.Unmarked tolerance accord with GB/T1804-m 5. Electric pick gun commutator resistance: 500V, more than 50MΩ 6. Spin test: do spin test for the commutator under 140 centigrade, the speed is 5000RPM, the test continues for 3min. After testing, the deviation of outer diameter is less than 0.015, the deviation between bar and bar is less than 0.005. 7. Voltage test: bar to bar 500V, bar to bore 1500V, without breakdown and flashing.