# Accurate Modeling, Operation Laws and Commutation Timing Matching for Concrete Pumping Systems
## 3 Results and Discussion
### Commutation timing optimization
#### 3.3.3 Optimization results  
Figure 16 reveals the correspondence between pumping and swing at different stages before and after optimization. There are five stages during pumping:  
S1: The swing cylinder (distribution valve) does not move, the spectacle plate and cutting ring overlap, the left main cylinder advances just past the detection side point,  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Before Optimization** & **After Optimization** \\ \hline Acc. volume & 10 L & 13 L \\ Acc. charging pressure & 100 bar & no change \\ Swing valve throttle orifice & 12 mm & 14 mm \\ Total buffer length & 30 mm & no change \\ Buffer length & 15 mm & 10 mm \\ Quick oil inlet hole & 6 mm & 10 mm \\ Reversing pressure & 80 bar & 50 bar \\ \hline \hline \end{tabular}
\end{table}
Table 2: Optimization parameters of the CPS.  
Figure 15: Erosion wear of the CPS.  
pumping high-pressure concrete into the distribution valve, and the right main cylinder sucks concrete from the hopper.  
S2: The left main cylinder continues to advance while the distribution valve begins to swing counterclockwise and the faceplate and cutting ring begin to separate.  
S3: The main cylinder moves to the end, ready to change direction, and the distributor valve continues to oscillate counterclockwise.  
S4: The main cylinder reverses direction, the left main cylinder sucks up the concrete and the right main cylinder pumps the concrete; part of the concrete is pumped into the distributor valve and part of the concrete escapes through the gap between the spectacle plate and the cutting ring into the hopper.  
S5: The distribution valve swings into place, the spectacle plate and cutting ring are reunited and the right-hand main cylinder pumps the material normally.  
Figures 17 and 18 show the displacement and velocity curves of the main cylinder and swing cylinder before and after optimization. Figures 14 and 15 have a corresponding relationship.  
From S2 to S4, the swing cylinder moves at high speed, the distribution valve and main cylinder outlet are separated and then closed and there is a large gap through which the high-pressure concrete leaks into the hopper. The problem with this process is mainly leakage. In fact, there is always leakage during the swing process, so the swing time determines the leakage and system efficiency. Figure 15 shows that after optimization, the swing time is reduced from 196 ms to 155 ms, the main cylinder switching point is delayed from 1/2 to 2/3 of the swing interval and the leakage stroke of the main cylinder is reduced from 128 mm to 69 mm, which effectively improves the pumping efficiency.  
Figure 16: The relationship between pumping and oscillation at different stages: (**a**) before optimization and (**b**) after optimization. (red and orange represent high pressure, dark blue represents medium pressure, light blue represents low pressure, and the arrows represent the direction of motion).  
Figure 17: System reversing sequence curves before optimization: (**a**) main cylinder displacement and swing cylinder velocity and (**b**) main cylinder velocity.  
Figure 18: System reversing sequence curves after optimization: (**a**) main cylinder displacement and swing cylinder velocity and (**b**) main cylinder velocity.  
of erosion wear. Figure 15 shows that after optimization, the low-speed slip time is reduced from 60 ms to 33 ms, effectively reducing the erosion wear.  
The proposed optimization scheme of commutation timing has been proven in the market with a significant increase in the life of wear parts, including a 93% increase in the average life of spectacle plates and a 200% increase in the average life of cutting rings.