Lightweight design requirements for new energy vehicle wheel hub molds

Lightweight design requirements for new energy vehicle wheel hub molds
New energy wheels need to balance low wind resistance, large diameter, and high load, and the mold needs to maintain fatigue life while reducing weight by 8% -12%.
Mold challenges caused by changes in shape
To reduce wind resistance, new energy vehicles often use large enclosed surfaces or low wind resistance spokes on the wheels. The larger the enclosed surface, the more difficult it is to exhaust the cavity.
Enclosed areas are prone to suffocation, resulting in insufficient watering or air pockets. The number of exhaust plugs is usually increased by 30% -50% compared to conventional wheel types.
After the spokes become thinner, the aluminum liquid process becomes longer. The filling time needs to be recalculated, and simply using the parameters of the fuel wheel type is often not qualified.
Load increase requires higher density
The battery pack increases the overall weight of the vehicle by 200-400kg, and the radial load on the wheel hub correspondingly increases. The number of cycles required for fatigue testing is more stringent.
The density of low-pressure casting is no longer sufficient for some high-end car models, and differential pressure or low-pressure plus local pressurization schemes are more common in such projects.
The tolerance for looseness at the root of the spoke decreases. The tightening of X-ray judgment from level 2 to level 1 is not uncommon in new energy projects.
The implementation path of weight loss
The weight reduction mainly comes from the optimization of spoke thickness and wheel rim wall thickness, with a common range of 8% -12%. For every 0.5mm reduction in wall thickness, a single piece will lose approximately 0.4-0.6kg in weight.
After the wall thickness is reduced, the cooling uniformity of the mold is required to be improved. The temperature difference on the surface of the mold cavity should be controlled within 10 ℃, otherwise cold insulation may occur in thin areas.
Xinfeng Mold will first evaluate the filling and solidification after thinning through simulation on new energy wheel hub molds, and then determine the waterway and gate scheme.
Combination of large diameter and low flatness ratio
New energy vehicles prefer 19-21 inch wheels, with a decrease in flatness ratio. As the width of the wheel rim increases, the length of the wheel rim forming section of the mold also lengthens.
The demolding resistance of wide wheel rims is greater. The demolding slope needs to be increased from the conventional 1 ° to 1.5 ° -2 °, otherwise it is easy to scratch the surface.
After widening the wheel rim, the weight of the mold increases. The lifting and changing fixtures need to be upgraded synchronously and cannot use the old specifications.
Surface treatment and appearance requirements
New energy vehicles have higher requirements for external appearance, and the wheels are often fully coated or polished with a glossy finish. The polishing level of the cavity surface needs to be correspondingly improved.
The precision machining surface requires the surface roughness of the casting to be below Ra3.2 μ m, and the cavity polishing needs to be below Ra0.8 μ m, which increases the processing time by about 20%.
The selection of coating should consider the balance between demolding and appearance. Excessive coating thickness can affect replication accuracy, usually controlled within 2-5 μ m.
Verify rhythm
The development cycle of new energy projects is tight, often compressed to 3-4 months from T0 to mass production. Mold design and simulation must be parallel and cannot wait in series.
The first article verification includes four categories: size, X-ray, airtightness, and fatigue. The fatigue test cycle is the longest, usually requiring 4-6 weeks.
Suggest locking key parameters at T0 stage and only making minor adjustments at T1. Repeated major revisions will drag down the entire project node.
Frequently Asked Questions
Q: How much weight can new energy wheel hubs reduce?
Answer: Commonly 8% -12%, limited by load and shape.
Q: Why is it harder to exhaust?
Answer: As the sealing surface increases, the exhaust plug needs to be increased by 30% -50%.
Q: What are the most common problems after thinning?
Answer: Insufficient cold insulation and pouring, the temperature difference in the mold cavity needs to be controlled within 10 ℃.
Question: What is the required demolding slope?
Answer: Wide wheel rims are recommended to be 1.5 ° -2 °.
Q: How long does the fatigue test take?
Answer: Usually 4-6 weeks is the main bottleneck of the development cycle.
Question: Is differential pressure technology necessary?
Answer: High load vehicles are more commonly used, while conventional vehicles can meet low pressure requirements.
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