Key points for timing debugging of vacuum valves in low-pressure casting molds for new energy structural components | Negative pressure control of LPDC vacuum filling molds
The timing mismatch of the vacuum valve in the vacuum LPDC mold for new energy structural components has resulted in insufficient vacuum degree of 45%, as well as batch defects in gas entrapment and cold insulation.
The vacuum is opened more than 0.18s after the aluminum liquid reaches the exhaust front, and the front oxide film has been closed, making it impossible to extract gas. The trapped gas is trapped inside the casting.
The vacuum duration is too long, and the aluminum liquid is sucked into the vacuum pipeline by negative pressure, blocking the filter element. After a single blockage, the vacuum extraction efficiency decreases by 55%.
When the vacuum valve is opened, the temperature of the mold cavity is lower than 175 ℃, and water vapor is sucked in along with the gas, resulting in a significant increase in the probability of hydrogen gas pores.
The peak vacuum negative pressure exceeds -0.092MPa, causing uncontrolled filling speed of aluminum liquid, intensified turbulence, and an increase in oxidation inclusion defects.
The timing of vacuum pressure relief lags behind the sealing time at the solidification front of the casting, and the continuous negative pressure during the solidification shrinkage stage can easily induce internal shrinkage.
Vacuum assisted low-pressure die-casting molds (LPDC) are commonly used for thin-walled gas tight parts such as new energy shells and brackets, and are the fastest-growing category of overseas inquiries in recent years; Counter pressure casting molds (CPC), differential pressure casting molds for wheel hubs, low-pressure casting molds for wheel hubs, gravity casting molds, motorcycle wheel hub casting molds, aluminum alloy wheel hub molds, aluminum casting forming molds, low-pressure casting tooling molds, and vacuum systems are rarely configured for wheel hub projects. Zhejiang Xinfeng Machinery is equipped with multiple sets of vacuum molds for Mexican new energy orders. The timing parameters cannot be copied directly from other schemes, and must be matched with filling curves and casting wall thickness gradients. Classification setting of vacuum pipeline filters, pre coarse filter blocking aluminum slag, precision filter capturing fine dust; The blockage of the filter element will result in the inability to increase the vacuum degree, which is a high-frequency hidden fault. The vacuum sealing surface rubber strip must be maintained separately. Under negative pressure conditions, air leakage is more sensitive than under normal pressure molds, and even small gaps can lower the vacuum platform. Many customers blindly pursue higher negative pressure, thinking that the higher the vacuum, the better the quality. After exceeding the critical negative pressure, turbulent inclusion defects actually increase. The priority for vacuum timing debugging is to collect pressure curves and compare them with the filling animation CAE. Lock the vacuum opening window at 0.08-0.12 seconds before the aluminum liquid reaches the exhaust port. North American customers have strict air tightness requirements, and vacuum mold technical documents, timing curve records, and vacuum degree logs need to be delivered with the goods.
FAQ
1. Question: What is the reference time difference for vacuum opening relative to the front edge of the aluminum liquid?
Answer: Priority should be given to opening 0.08-0.12 seconds before the aluminum liquid reaches the forefront.
2. Question: What is the upper limit of the safe peak value of vacuum negative pressure?
Answer: Negative pressure should not exceed -0.092MPa to prevent turbulence.
3. Question: What is the bottom temperature line of the vacuum opening cavity mold?
Answer: When opening the vacuum, try to keep the mold temperature ≥ 175 ℃ to reduce water vapor.
4. Question: What are the consequences of vacuum suction aluminum entering the pipeline?
Answer: If the filter element is clogged, the extraction efficiency will decrease by about 55%.
5. Question: Is vacuum commonly used for wheel hub molds?
Answer: Conventional wheel hub molds are generally not equipped with vacuum systems.
6. Question: What is the core basis for vacuum mold debugging?
Answer: Coordinated calibration with pressure curve and CAE filling timing.
