Die casting molds are essential for forming molten aluminum into precise and complex shapes. They define the product’s geometry, ensure dimensional accuracy, and improve surface quality. In aluminium alloy die casting, the quality of the die casting mold determines the strength, porosity, and dimensional stability of final products, especially for mass production.
This article will explore the main types of die casting molds, their structural components, design points, manufacturing processes, and daily maintenance methods. Read on to learn how each link affects the quality of aluminium die casting components.
Types of Aluminum Die Casting Molds
Single-Cavity Dies
Single-cavity dies only produce one product per production cycle and are suitable for prototype development or small batch production.
This mold has low cost and fast installation speed, which helps to verify part design before mass production of die casting products.
Multi-Cavity Dies
This die contains multiple identical cavities, which can cast several identical die casting parts simultaneously in each production cycle.
It significantly improves production efficiency and reduces unit cost, especially for large-volume orders that need to be delivered quickly.
Combination Dies
The multi-cavity combination die integrates the cavities of multiple part structures in one mold, making it suitable for complex systems or multi-part product lines.
It reduces the number of mold changes and improves the rhythm of the die casting process.
Unit Dies
Unit dies use a standard mold base and are equipped with a replaceable core or cavity insert, ideal for products with a variety of design changes.
This flexible structure not only reduces mold investment but also simplifies the maintenance process and shortens the delivery cycle.
Structure and Key Components of Die Casting Mold
Two Halves Structure: A Side and B Side
The mold consists of a fixed A side (cover mold) and a movable B side (ejector mold). The A side is connected to the injection system, while the B side contains the ejector mechanism.
Accurate alignment ensures mold sealing, dimensional accuracy, and prevents flash or misalignment.
Core and Cavity
The cavity determines the product’s outer shape, and the core forms the internal holes, grooves, and other structures—together they define the product geometry in high pressure die casting.
Ejector System
Once the casting cools, it is ejected from the mold by an ejector pin, plate, inclined ejector, or lifter. Smooth ejection prevents deformation or surface defects.
Runner and Gate System
The runner guides molten aluminum into the cavity, and the gate controls the feeding position. An optimized system ensures filling speed, flow balance, and quality casting results.
Cooling System
Internal cooling channels regulate temperature and solidification rate. Proper cooling shortens cycle times, minimizes deformation, and extends mold life.
Exhaust and Overflow System
The exhaust groove expels air and gas, while the overflow groove collects excess metal. This reduces porosity, gas inclusions, and surface defects in die casting products.
Sliders
Mechanically or hydraulically driven sliders enable complex shapes such as undercuts and side holes, and assist with smooth demolding.
Key Points of Aluminum Die Casting Mold Design
Material Selection
High-performance mold steels like H13 and SKD61 offer excellent thermal fatigue resistance and wear durability. Copper alloy plugs can enhance cooling in high-temperature zones.
Product Geometry
Proper draft angles ensure smooth ejection, while uniform wall thickness helps prevent shrinkage and warping.
Reinforcements like ribs and fillets reduce stress concentration and extend mold life.
Rounded Corners and Chamfered Design
Sharp corners increase the risk of cracking. Rounded transitions improve metal flow and mold durability, which helps boost mechanical strength in aluminium die casting components.
Runner and Exhaust System Design
Balanced gating and efficient exhaust paths minimize defects like cold shuts, gas porosity, and underfills, common challenges in the die casting process.
Cooling Channel Layout
Cooling channels should be placed near heat concentration areas to stabilize cycle times and reduce deformation. Well-designed cooling also lowers maintenance frequency.
Shrinkage Compensation
Aluminum shrinks as it cools. The mold cavity must be designed slightly larger to compensate for shrinkage, ensuring the final die casting parts meet precise dimensional requirements.
Aluminum Die-Casting Mold Manufacturing Process
Mold Design
During design, 3D modeling and mold flow analysis help predict flow behavior, identify cooling bottlenecks, and eliminate potential casting defects.
Combined with DFM analysis, the mold structure can be optimized, manufacturability can be improved, and demolding and cooling effects can be improved.
Precision Machining
CNC and EDM are the primary processes. CNC handles large surface areas, while EDM is ideal for intricate and tight tolerance features, ensuring accuracy and surface quality in die casting mold production.
Heat Treatment
Post-machining heat treatments like quenching and tempering improve wear resistance, hardness, and fatigue strength, crucial for long-lasting die casting mold durability.
Assembly
Accurate assembly ensures sliders, ejectors, and guide systems function properly. Well-aligned mold components prevent flash and dimensional errors of aluminum die casting parts.
Mold Trial and Optimization
Trial runs assess filling completeness, porosity, and cooling balance. Based on results, further optimization ensures molds are ready for large-scale high pressure die casting production.
Common Mold Failures and Solutions
Thermal Cracks
Failure: Thermal cracks often occur in high-temperature zones due to frequent and rapid temperature fluctuations, leading to structural damage and reduced mold life.
Solution: Use mold steels with high thermal fatigue resistance, such as H13 or SKD61, and optimize the cooling system to maintain stable mold temperatures.
Erosion and Wear
Failure: Molten aluminum gradually wears down the mold surface, especially in high-impact areas like gates and sharp corners, affecting part precision and surface quality.
Solution: Apply surface treatments such as polishing or plating, and use high-hardness materials to enhance wear resistance and extend mold lifespan.
Flash Problem
Failure: Flash occurs when molten metal leaks from the mold parting line, typically due to poor mold closure or inadequate clamping force.
Solution: Ensure accurate mold alignment, increase clamping force if necessary, and regularly maintain the parting surface to prevent leakage.
Mold Misalignment
Failure: Mold misalignment can cause dimensional inaccuracies, flash, and difficulties in part assembly. It is usually due to worn guide pins, bushings, or positioning elements.
Solution: Conduct regular inspections of all positioning components and maintain precise mold assembly to prevent misalignment issues.
Mold Maintenance and Life Management
Factors Affecting Mold Life
The mold life is affected by the temperature of the aluminum alloy, material wear, cooling effect, and maintenance frequency.
Poor cooling or frequent use can easily lead to mold cracking and failure.
Daily Maintenance
After each production, the mold surface residue should be cleaned, the guide pins, sliders, ejectors, and other parts should be checked, and the worn parts should be lubricated and replaced in time.
Mold Refurbishment
After the mold is worn, it does not need to be replaced as a whole. It can be partially refurbished by polishing, repairing, or replacing the inserts to reduce costs and shorten downtime.
CEX Casting Mold Manufacturing Capabilities
CEX Casting is a professional die casting manufacturer in China, offering tailored mold services including in-house mold design, flow simulation, DFM optimization, and ongoing maintenance.
Our modular die casting mold systems support quick product adjustments and short lead times.
With advanced CNC and EDM capabilities, we can produce complex and high-precision aluminium die casting components, optimizing both cost and efficiency.
We also provide comprehensive refurbishment and maintenance services, including cavity repair, insert replacement, and inspection protocols, to ensure long-term mold stability.
Conclusion
High-quality molds are essential to achieving precise geometry, excellent surface finishes, and reliable mass production in high pressure die casting.
As a leading die casting company, CEX Casting delivers complete one-stop solutions for die casting products, combining technical expertise with flexible services.
Contact us today to elevate your next aluminium alloy die casting project with our tailored die casting mold solutions.