To enhance the control precision of a HPHT Hydraulic Cubic Press during the synchronous filling process, improvements can be made in several areas, including measurement technology, feedback control, intelligent algorithms, and automation control.
Here are the detailed improvement methods and ideas:
Detailed Improvement Methods and Ideas
High-Precision Detection of Six-Cylinder Displacement
Although displacement sensors have been used on six-sided anvil presses for nearly a decade, their primary application has been for rapid traverse control and non-critical system parameter measurement. They haven't been truly integrated into core high-pressure system control due to poor repeatability over large measurement ranges and a lack of application scenarios for small-range, high-precision detection.
During the filling process, the piston stroke typically ranges from 3 mm to 5 mm. Within this measurement range, high-precision displacement sensors can effectively provide accurate measurements, offering a reliable basis for achieving displacement synchronization.
High-Precision Pressure Sensors and Precise Pressure Control
Current filling control methods typically involve setting a fixed pump displacement, which rapidly fills the working cylinders with hydraulic oil. This often leads to uncontrolled pressure increases in the working cylinders during pyrophyllite compression, with actual filling pressures frequently exceeding the set value by more than 20%.
During the filling process, synchronization is highly sensitive to pressure changes. Therefore, adopting high-precision pressure sensors with an accuracy of 0.01 MPa in the control system and precisely controlling the filling pressure rise rate are crucial for improving the synchronous filling control level.
Proportional Valves Replacing Throttle Valves for Single-Cylinder Flow Control
Currently, the unconnected filling method uses six manual throttle valves to adjust the flow rate for each cylinder, resulting in poor control precision, low automation, and weak anti-interference capability.
By replacing throttle valves with electro-hydraulic proportional valves, online automatic adjustment of flow rates for each working cylinder can be achieved. This not only effectively overcomes problems such as poor precision, repeatability, and stability but also eliminates tedious manual adjustments, ensuring optimal filling synchronization for each synthetic block.
Six-Cylinder Displacement Comparison and Correction Algorithm
Based on the technologies of using displacement sensors to collect piston displacement and replacing throttle valves with proportional valves, the displacement sensors can continuously feed piston displacement signals back to the control system during the filling process.
The system can compare the displacement of all six working cylinders and promptly adjust any cylinder whose displacement falls outside the acceptable range, correcting its displacement to ensure synchronous movement of all six cylinders. This algorithm can effectively achieve automatic six-cylinder synchronous control.
Hybrid Control Method Combining Pressure and Displacement
The ultimate goal of synchronous filling control is to achieve synchronous movement of the top anvils. In practice, displacement changes are achieved by adjusting single-cylinder flow rates, and the fundamental reason for flow changes lies in pressure variations. Therefore, the synchronous filling process control of a six-sided anvil press is a comprehensive process that simultaneously controls pressure, flow, and displacement.
Previous control methods often focused on only a single variable, such as pressure or flow, leading to suboptimal control results. The correct approach is to leverage the computational capabilities of the electronic control system to dynamically distribute the flow rate to each working cylinder while ensuring a stable increase in filling pressure, thereby achieving precise synchronous control of all six-cylinder displacements and effectively improving filling synchronization.
The technical value of improving filling synchronous control precision is reflected in the following aspects:
Improved High-Pressure Seal Stability: Enhanced synchronous filling control technology can effectively improve the uniformity of pyrophyllite compression during the filling stage, leading to a more symmetrical seal edge formation. This significantly improves the high-pressure sealing performance of the synthetic blocks, reduces the likelihood of "explosions," enhances safety, and lowers production costs.
Improved Uniformity of Pressure Gradient Field: Improved synchronous filling control technology helps stabilize the internal pressure gradient field of the synthetic blocks. This is particularly beneficial for producing large-sized products with large synthetic blocks, as it can maximize the utilization rate of the high-pressure cavity volume and increase product output.
Improved Repeatability of Side-Heated Carbon Tube Resistance: Poor filling synchronization can lead to random degrees of cracking or breakage of heating carbon tubes during the filling process. These damages create contact resistance, resulting in non-uniform temperature field distribution, which in turn affects the quality stability of high-end products (such as high-grade composite sheets). By improving synchronous filling control technology, the random damage to heating carbon tubes can be minimized, effectively improving the repeatability of resistance distribution and thus enhancing the quality of high-end products, providing technical assurance for domestic product manufacturers.