axis of levelling bubble

例句：

1. 1.The axis of the machine is perfectly aligned for easy adjustment.
   机器的轴线完美对齐，便于调整。
2. 2. The bubble was a perfect circle, indicating that the gas was evenly distributed.
   气泡是一个完美的圆，表明气体分布均匀。
3. 3.During the leveling process, the bubble was carefully monitored to ensure accuracy.
   在平移过程中，气泡被仔细监控以确保准确性。