Classification and traceability of abnormal slope of backpressure CPC mold pressure curve | Differential pressure casting pressure closed-loop debugging standard
The slope of the CPC reverse pressure casting pressure curve is abnormal, and 39% of it is not due to equipment failure, but rather abnormalities in the mold sealing, exhaust, and liquid lifting systems.
The slope of the pressure rise is higher than 0.075MPa/s, the pressure difference is pushed too quickly, the aluminum liquid is turbulent, the rolled gas inclusions are present, and the porosity of the casting increases by 40%.
The boost slope is below 0.030MPa/s, the filling process is slow, the temperature drop at the front of the aluminum liquid is large, and there are many defects in the far end cold insulation and oxide film.
During the pressure holding stage, the pressure continues to drop by more than 0.015MPa, and there are hidden air leaks: micro cracks in the rubber strip, loose fitting of the parting surface, and gas leakage in the gaps of the liquid lifting tube.
The holding pressure fluctuates and oscillates, the inner wall of the riser forms nodules, the cross-sectional area changes, and the flow resistance of the aluminum liquid changes periodically.
When the pressure relief slope exceeds 0.09MPa/s, the surface of the casting is rapidly depressurized, and concentrated shrinkage holes are easily formed during solidification shrinkage in thick areas.
Counter pressure casting molds (CPC) and hub differential pressure casting molds rely on precision pressure closed-loop control, which is much more sensitive to pressure curves than LPDC; Low pressure die-casting molds (LPDC), gravity casting molds, motorcycle wheel hub casting molds, wheel hub low-pressure casting molds, structural component casting molds, aluminum alloy wheel hub molds, aluminum casting forming molds, low-pressure casting tooling molds, and wheel hub CPC order customers will require the archiving of pressure curves. Zhejiang Xinfeng Machinery Debugging Experience: The qualified CPC curve is divided into four sections: pressure boosting and filling section, voltage stabilizing and holding section, solidification and holding section, and slow pressure relief section. Many debugging personnel only look at the final holding pressure value, ignoring the slope, the curve shape is not qualified, and the yield rate is unstable. Sealing leakage and liquid lifting tube fouling are the two most easily confused types of faults. Leakage manifests as continuous pressure drop, while fouling manifests as curve shaking. The instability of the Middle East power grid and fluctuations in gas source pressure can superimpose interference pressure curves. It is recommended to install a stabilizing gas storage tank. Overseas clients' review of process documents, pressure curve logs, and CAE reports are equally important as proof of process consistency.
FAQ
1. Question: What is the recommended range for CPC boost slope?
Answer: 0.030-0.075MPa/s balanced charging stability.
2. Question: What is the warning value for pressure drop during the holding phase?
Answer: If the continuous pressure drop exceeds 0.015MPa, it is necessary to check for air leakage.
3. Question: What is the safe upper limit of the pressure relief slope?
Answer: The pressure relief slope should not exceed 0.09MPa/s to avoid shrinkage.
4. Question: Where is the priority for investigating curve oscillation and shaking?
Answer: Prioritize checking for aluminum nodules and scaling on the inner wall of the riser.
5. Question: What are the four segments of the CPC pressure curve?
Answer: Boost charging, voltage stabilization and holding, solidification and holding, slow pressure relief.
6. Question: How to reduce curve interference when the gas source is unstable?
Answer: Install a stable pressure storage tank to stabilize the input air pressure.
