## 4 Application of the Automatic Assembly Production Line
### Quality Improvement of the Valve Core Measurement Process  
The switch stroke is one of the most important indicators of a valve. Due to the fact that the movable component of the valve stem is supported by a plate spring cantilever, the valve stem is always in an elastic support state. In traditional assembly methods, manual measurement of the stroke uses a dial gauge to indirectly measure the measuring rod extending from the valve inlet channel. The measuring head of the dial gauge has a certain downward force on the valve stem. When the valve opens, it first needs to overcome this additional force before the valve can open. In addition, due to the inherent gap between the measuring rod and the inlet channel of the valve, the tilt of the valve stem and the movement of the valve core switch can cause inherent deviation in the measurement position of the measuring rod. Figure 16 shows an example of the relationship between the measuring rod, valve core, and valve inlet end of a certain valve with a calculated deviation of about 2 \(\upmu\)m.  
The three valves previously measured manually were measured using an improved non-contact method, and the stroke data showed deviations of \(-0.020\) mm, \(-0.015\) mm, and \(-0.011\) mm, respectively. This has a significant impact on high-precision microstructural valves.  
The influence of the above inherent factors, combined with the error-proneness of manual operation, is particularly prominent for micro flow control valves with micrometer stroke and proportional adjustment micro-displacement valves. In addition, for proportional adjustment valves, due to the need to measure values from multiple output points, the manual measurement method requires the cooperation of two people and takes two hours to complete, resulting in low efficiency. By adopting a measurement and testing mechanism, the valve core stroke measurement, electrical performance testing, and running-in process  
Figure 15: Implementation diagram of a certain valve shell connection welding point.  
can be continuously completed at the same workstation, avoiding inherent deviations in stroke measurement and improving the measurement accuracy to the visual value of 0.1 \(\upmu\)m. Moreover, for proportional valves with a high-testing workload, automatic testing can be completed within 2 min, greatly improving work efficiency.  
Figure 17 shows the valve displacement curve measured using traditional dial gauge. Figure 18 shows the non-contact measurement curve of valve displacement using an automatically assembled laser displacement sensor. The scale division rate of laser displacement sensor is 0.1 \(\upmu\)m.  
From the above figure, it is shown that using a laser displacement sensor to automatically measure the valve displacement curve is smoother, the curve has no fluctuations, and the measurement is more accurate. The displacement of the valve using a dial gauge is 161 \(\upmu\)m. And the displacement of the valve using laser displacement sensors is 193 \(\upmu\)m. The measurement error between the two methods is 32 \(\upmu\)m. Therefore, the result by using laser displacement sensors to measure valve displacement is more accurate.  
Figure 16: Position relationship diagram of the measuring rod, valve core, and inlet end of a certain valve.  
Figure 17: The valve displacement curve using traditional dial gauge.