hardness control

例句：

1. 1. The engineeris responsible for maintaining the hardness controlof the machine.
   工程师负责维护机器的硬度控制。
2. 2. In order to improve the qualityof the product, we need to controlthe hardness of the material.
   为了提高产品的质量，我们需要控制材料的硬度。
3. 3. Thehardness control system is crucial for ensuringthe safety and efficiency of the machinery.
   硬度控制系统对于确保机械的安全和效率至关重要。