Introduction
In today's market dominated by integrated die-casting, structural components, and three-electric systems, discussing development experience of traditional fuel-powered vehicle cylinder blocks may seem cliché. However, ten years ago, cylinder block development was no less challenging than any emerging product today. As a core and representative component of fuel-powered vehicles, there's still much to learn about its mold and process development characteristics. I hope following sharing will be helpful to fellow die-casting professionals. Die-casting principles are universal, and good design concepts should be universally applicable, adapting to changing circumstances.

1. Basic wall thickness of a cylinder block is typically 3.8-4.5mm, which is ideal for filling in die-casting.

 

2. Avoiding large-scale shrinkage cavities and leakage in thick areas such as crankshaft and oil passages is a key consideration in gating and process design.

 

Thick and large areas of crankshaft

 

Thick and large areas where oil passages intersect
3. Surface porosity on cylinder head surface also requires continued attention due to obstruction of aluminum filling by water channels, vent holes, and cylinder bores.

 

4. Leakage issues caused by poorly controlled shrinkage holes in crankshaft and cylinder head mounting holes, which intersect with oil passages, and poor structural density can lead to substandard mechanical properties.

 

5. All cylinder blocks have cylinder bores at their center axis, effectively dividing the entire product into two separate, opposing parts. Obstruction of cylinder bores during die-casting filling process is one of the most influential factors in selecting a pouring system for cylinder blocks (except in very rare cases).

Based on structural and parting characteristics of cylinder block, pouring direction for cylinder blocks can be either single-sided or double-sided. While some experimented with center-feeding many years ago, these two types are currently mainstream after years of practice. Both feed methods share advantage of using an eagle-beak, along-the-wall pouring gate. Advantages and disadvantages of each type of gate are discussed below.

 

1) Advantages: Since molten aluminum is sequentially filled from one side to the other, a large exhaust and vacuum system on the top slider facilitates effective exhaust and slag removal throughout filling process.
2) Advantages: Single-Sided Feeding often selects main oil channel, which has more complex features, for feeding. Therefore, quality near key areas such as main oil channel is generally better. This also conforms to pouring design principle of prioritizing key areas for feeding.
3) Disadvantages: As mentioned above, due to obstruction of cylinder bore to flow pattern, only filling channel for single-sided feed molten aluminum is crankshaft. This is equivalent to dividing the top side into several sections, where molten aluminum converges. If cylinder bore is used as center, the overall molding quality of top side will inevitably be inferior to that of feed side. Therefore, with this feeding method, density of the entire product decreases along feed direction. Problem of shrinkage cavities at the far end, which causes leakage, is often unsolvable and can only be reduced through impregnation.
4) Disadvantages: Because of these issues, single-side feeding often requires higher speeds and pressures to compensate for insufficient filling channel, which indirectly reduces mold life, at least on feed side.

 

1) Advantages: Due to obstruction of cylinder bore, part can be considered two separate parts, one on the left and one on the right. Therefore, each side of double-sided feed system is responsible for forming only one side. This method significantly improves microstructure uniformity of the entire part. It also optimizes pressure transmission and shrinkage compensation in thick areas, such as crankshaft, on both sides.
2) Advantages: Double-sided feeding allows for a larger feeding area than single-sided feeding, which reduces need for high-speed and high-pressure process conditions. Compared to single-sided feeding, which requires high speed and high pressure to compensate for lack of a sufficient filling channel, this method significantly reduces mold erosion during filling process.
3) Advantages: Double-sided feeding takes longer than single-sided feeding, which expands die-casting process window.
4) Disadvantages: Double-sided feeding, with its unidirectional top-down filling process, is not conducive to exhaust and slag removal, can easily cause air entrainment on cylinder head surface and top of roof.

 

From above comparison, it's clear that double-sided feeding outperforms single-sided feeding in terms of both casting quality and mold life. Single-sided feeding, however, is constrained by product's inherent structure and cannot be altered, while double-sided feeding only addresses degassing issue associated with this system.

1. Filling Sequence Control: To address degassing, the first consideration is filling sequence of each ingate from front to rear. From the first ingate to the last, a clear gradient must be maintained, as shown in following figure:

 

2. Gate design for aforementioned filling sequence: Filling sequence and gradient must be strictly controlled. Key considerations are proper guidance of each ingate, especially the first two. Molten aluminum flows preferentially toward areas with low backpressure. Since ingates are thin, majority of molten aluminum typically fills main runner first, followed by individual ingates. Therefore, guidance design must first overcome backpressure.
Principle is simple: it harnesses centrifugal force of circular motion. When a high-speed circular object breaks free, it moves along tangent of circle at point of breakaway. Therefore, core of this type of pouring arrangement is to utilize this principle to guide the first few gates, as shown in figure:

 

3. Exhaust and Vacuum Setup:
1) Exhaust Setup: As described above, double-sided feeding involves unidirectional filling of molten aluminum from crankshaft surface to cylinder head surface. Due to obstructions such as cylinder bore, water channels, and vent holes, while controlling filling sequence can greatly optimize exhaust, significant air entrapment still occurs on cylinder head surface during filling. Therefore, vacuum exhaust channel should cover at least two-thirds of cylinder head width, actively exhausting gas from cavity through vacuum.

 

2) Vacuum Setup: Optimizing gate and exhaust channel significantly reduces vacuum requirement for this solution, requiring only conventional space exhaust plates for vacuum extraction.

 

1. Advantages of this feeding method: First, it solves problems of uneven microstructure caused by pressure transmission and small feeding channels associated with single-sided feeding. Second, it optimizes filling gradient compared to conventional double-sided feeding, significantly resolving difficulty of exhausting air with double-sided feeding. Furthermore, it significantly improves service life of mold.
2. Practical application results of this feeding method: Through above optimizations, combined with a suitable die-casting process, this method significantly reduces impregnation rate of produced castings while utilizing lower speeds and pressures than single-side feeding, thereby improving microstructure and performance. Following figure shows anatomy of crankshaft area at various gears in a real-world example:

 

 

3. When combined with a suitable die-casting process, this method is applicable to over 95% of cylinder block products and can be replicated.