Low pressure mold for wheel hub, thin rib position of spoke, hot joint offset, and layout strategy of conformal cooling inserts | A356 wheel hub shrinkage reduction and loosening
The offset of the hot joint at the junction of the hub spoke thin ribs and the wheel core is a typical location detected by 40% X-ray shrinkage.
The rounded corner R at the root of the spoke is less than 3mm, the cross-section undergoes a sudden change, the solidification sequence is disordered, and the feeding channel of the riser is closed in advance.
The cooling insert is too far from the root of the spoke, and the hot spot cannot be prioritized to take away heat, resulting in an isolated solidification area without any additional shrinkage.
The cooling of multiple spokes is asymmetric, and the solidification time difference of each spoke exceeds 12 seconds, resulting in significant fluctuations in the yield rate.
The flow rate of the cooling water circuit is consistent, but the heat transfer area is uneven, with some areas having strong radiation cooling and some areas having weak radiation cooling, resulting in random drift of the hot spot.
Blindly increasing the cooling flow rate leads to rapid crust formation on the surface and closure of internal liquid phase channels, resulting in isolated shrinkage cavities inside.
Low pressure die-casting molds (LPDC), hub low-pressure casting molds, and hub differential pressure casting molds are the main types. Reverse pressure casting molds (CPC), gravity casting molds, motorcycle hub casting molds, structural component casting molds, aluminum alloy hub molds, aluminum casting forming molds, and low-pressure casting tooling molds are also used. 80% of X-ray defects in hub projects are concentrated at the root of the spokes. Zhejiang Xinfeng Machinery Debugging Principle: Prioritize CAE solidification simulation to lock the position of the hot spot, align the cooling inserts with the hot spot, rather than evenly arranging them. Priority should be given to enlarging the rounded corners at the root of the spokes to R4-6mm, with a smooth transition to maintain an open supplementary channel. Using independent throttling to control the cooling water of each spoke insert, adjusting the cooling intensity separately to balance the solidification timing. The stronger the cooling, the better. It is necessary to match the holding time and filling speed for coordinated debugging, and find the sequential solidification window. Overseas high-end wheel hub customers will submit solidification simulation reports as mold acceptance materials for each wheel hub.
FAQ
1. Question: What is the recommended lower limit for the transition fillet at the root of the spoke?
Answer: Priority is given to R4 – 6mm, and it is not recommended to be less than R3mm.
2. Question: What is the alert value for multi radiation solidification time difference?
Answer: The solidification time difference of each radiation should not exceed 12 seconds.
3. Question: What is the basis for arranging cooling inserts?
Answer: The position of the hot spot in CAE solidification simulation shall prevail.
4. Question: Are there any side effects of cooling too much?
Answer: The outer shell rapidly solidifies, and the internal liquid phase channel is sealed, resulting in isolated shrinkage cavities.
5. Question: How to independently adjust multi spoke cooling?
Answer: Each radial waterway is equipped with an independent throttle valve.
6. Question: Is there a high incidence area of wheel hub X-ray shrinkage?
Answer: The root of the intersection between the spokes and the wheel core.
