Aluminum die casting is a casting method that efficiently manufactures products with complex shapes by injecting molten aluminum alloy into a mold at high speed and high pressure. It is used in a wide range of fields such as automobile parts, home appliances, and industrial equipment.
In die casting design, it is important to achieve a good balance of three elements: strength, accuracy, and thin-walledness. Strength contributes to product durability, accuracy to part fit and functionality, and thin-walledness to weight reduction and cost reduction.
This article explains specific design know-how for achieving strength, accuracy, and thin-walledness in aluminum die casting design. It provides practical information by summarizing the points in each process, such as material selection, structural design, CAE analysis, mold design, molding conditions, and quality control.
Strength Design
Strength design of aluminum die-cast products is a very important process in ensuring product reliability and safety. Products that meet the required strength characteristics can be realized by combining appropriate material selection, structural design, CAE analysis, surface treatment, and more.
| Item | Content | Points |
|---|---|---|
| Material Selection | Use alloys such as ADC12 and ADC10 | ADC12 excels in mechanical strength and castability, ADC10 in corrosion resistance. Properties can be adjusted with added elements. Set highly reliable standards with actual strength evaluation |
| Structural Design | Properly place ribs and bosses | Consider stress distribution for ribs, set wall thickness according to insert metal for bosses. Uniform wall thickness is important, with 1.0-2.5mm as a guideline |
| CAE Analysis | Evaluate strength with FEM analysis | Identify stress concentration points and predict fatigue strength |
| Surface Treatment | Anodizing, shot blasting, etc. | Improve corrosion resistance and hardness with anodizing, improve fatigue strength with shot blasting |
Material Selection
Alloys such as ADC12 and ADC10 are commonly used for aluminum die casting. ADC12 is used in a wide range of applications because it has high mechanical strength and excellent castability. ADC10 has excellent corrosion resistance and is suitable for products used in marine environments and outdoors.
The properties of the alloy can be adjusted by adding elements. For example, adding Cu increases strength but tends to decrease corrosion resistance. It is important to select the appropriate alloy according to the application.
Setting material strength standards is also an important process. Highly reliable standards can be set by performing actual strength evaluations and evaluating strength using test pieces created under the same manufacturing conditions as the actual product.
Structural Design
Structural design is an important factor in ensuring product strength. Rigidity can be increased and weight reduced by properly placing ribs and bosses.
Ribs should be designed considering stress distribution, rib structure, rib cross-sectional shape, environmental temperature, and more. The boss wall thickness should be set appropriately according to the insert metal material, as too thick can cause sink marks and too thin can reduce fastening force.
Uniform wall thickness is important, and sudden changes in thickness can cause stress concentration. The recommended range is adjusted according to the application, but generally, 1.0-2.5mm is a guideline.
CAE Analysis
CAE (Computer Aided Engineering) analysis is used to utilize member strength evaluation in product design. A design process that performs strength evaluation from the results obtained using FEM (Finite Element Method) analysis and performs product evaluation by prototyping in the final stage is effective.
In CAE analysis, it is important to identify locations where stress concentration is likely to occur and predict fatigue strength.
Surface Treatment
Aluminum die casting surface treatments include plating, polishing, chemical conversion, painting, anodizing, and more. Anodizing has the effect of increasing corrosion resistance and hardness, and can extend product life.
Shot blasting has the effect of removing fine defects on the surface and improving fatigue strength.
Precision Design
The precision of aluminum die-cast products is an important factor that affects product functionality and assemblability. To achieve high precision, various factors such as mold design, molding conditions, dimensional accuracy control, and quality control must be considered.
| Item | Content | Points |
|---|---|---|
| Mold Design | Gate position and runner shape, cooling system | Place gate position in a location that enables uniform filling, design runner shape to smooth flow. Control solidification speed by increasing cooling efficiency and improve dimensional accuracy |
| Molding Conditions | Temperature (molten metal temperature, mold temperature), pressure, injection speed | Suppress shrinkage and defects by properly managing molten metal temperature and mold temperature. In high-pressure die casting, pressure commonly reaches 100-200MPa. Prevent air bubbles and defects by injecting metal at an appropriate speed |
| Dimensional Accuracy | Tolerance, shrinkage | Dimensional tolerance of aluminum die casting is generally about ±0.1-0.2mm. Shrinkage rate is about 0.6-0.8%, which should be considered during design |
| Quality Control | Inspection and measurement | Use CT scanners and coordinate measuring machines to check for internal defects and dimensional accuracy. Suppress the occurrence of defective products |
Mold Design
Mold design is one of the factors that greatly affects product accuracy. The gate position and runner shape should be designed to optimize the flow of molten metal and enable uniform filling. The gate position is determined by considering the product shape, size, wall thickness, and more. The runner shape is designed to allow the molten metal to flow smoothly and suppress turbulence.
The cooling system plays a role in improving dimensional accuracy by keeping the temperature in the mold uniform and controlling the solidification speed. The cooling system design is performed by considering the mold material, shape, product wall thickness, and more.
Molding Conditions
Molding conditions are another important factor that affects product accuracy. Shrinkage and defects can be suppressed by properly managing the molten metal temperature and mold temperature. The molten metal temperature is set by considering the alloy type, product shape, wall thickness, and more. The mold temperature is managed to control the solidification speed of the molten metal and improve dimensional accuracy.
In high-pressure die casting, pressure commonly reaches 100-200MPa. By injecting metal at an appropriate pressure, air bubbles and defects can be prevented and the product density can be increased.
Injection speed also affects product accuracy. By injecting metal at an appropriate speed, air bubbles and defects can be prevented and uniform filling can be promoted.
Dimensional Accuracy
To ensure dimensional accuracy, it is necessary to design considering tolerances and shrinkage. The dimensional tolerance of aluminum die casting is generally about ±0.1-0.2mm. The shrinkage rate is about 0.6-0.8%, which should be considered during design.
Quality Control
Quality control is also an important factor. It is necessary to maintain product accuracy through inspection and measurement. Use CT scanners and coordinate measuring machines to check for internal defects and dimensional accuracy. This can suppress the occurrence of defective products and ensure product quality.
Thin-Walled Design
In recent years, with increasing environmental awareness, there is a trend towards demanding lighter products. In aluminum die casting, thin-walled design is one of the important themes. Thinning not only leads to cost reduction by reducing the amount of material used, but also contributes to improved fuel efficiency and exercise performance due to product weight reduction.
| Item | Content | Points |
|---|---|---|
| Product Design | Areas where thinning is possible, shape ingenuity | Thin areas where stress does not concentrate and where rigidity is not required. Compensate for strength reduction with ribs and reinforcing structures |
| Molding Technology | High-pressure die casting, vacuum die casting | Mold thin-walled parts with high-pressure die casting (about 0.6mm), prevent air bubbles and defects with vacuum die casting |
| Mold Design | Mold temperature control, flow path design | Control solidification with mold temperature control, uniform filling with flow path design |
| Material Properties | High-strength alloy | Suppress strength reduction due to thinning |
Product Design
In thin-walled design, first consider areas where thinning is possible. By thinning areas where stress does not concentrate and where rigidity is not required, weight reduction can be achieved while maintaining strength.
Shape ingenuity is also an important factor in thin-walled design. Strength reduction due to thinning can be compensated by appropriately adding ribs and reinforcing structures. Ribs not only increase product rigidity but also have the effect of improving molten metal flow.
Molding Technology
High-pressure die casting is a technology that forms thin-walled parts using high pressure. Thinning of about 0.6mm is possible, which greatly contributes to weight reduction.
Vacuum die casting is a technology that removes air from the mold to prevent air bubbles and defects and improve the quality of thin-walled parts. It suppresses strength reduction due to thinning and can manufacture higher quality products.
Mold Design
To form thin-walled parts, it is necessary to optimize mold temperature control and flow path design. By properly managing the mold temperature, the solidification of molten metal can be controlled and filling to thin-walled areas can be promoted. The flow path design needs to be devised so that molten metal flows smoothly and fills uniformly.
Material Properties
Since rigidity decreases due to thinning, selecting a high-strength alloy to compensate for strength is also an effective means. High-strength alloys suppress strength reduction due to thinning and realize lighter and higher strength products.
Thin-walled design is an important technology that contributes to product weight reduction and cost reduction, but there are also issues such as strength reduction and quality control. By selecting appropriate design methods and molding technologies and considering material properties, the disadvantages of thinning can be minimized and high-quality products can be manufactured.
Other Considerations
In aluminum die casting design, there are several other considerations besides strength, accuracy, and thin-walledness. By properly considering these factors, higher quality and higher performance products can be realized.
| Item | Content | Points |
|---|---|---|
| Stress Concentration | Tends to occur at shape change points such as corners and holes | Take measures such as providing fillets (curved surfaces) |
| Heat Treatment | Improves strength and toughness | Select heat treatment according to alloy and required properties, such as solution treatment and precipitation hardening |
| Surface Treatment | Improves corrosion resistance, wear resistance, and design | Plating, polishing, chemical conversion, painting, anodizing, etc. |
| Merits of Weight Reduction | Reduced transportation costs, reduced environmental impact | Fuel efficiency improvement effect can also be expected |
| Realization of Complex Shapes | Integral molding is possible | Reduction of number of parts, reduction of assembly man-hours, cost reduction, quality improvement |
| Global Production Support | Production with the same quality is possible at overseas bases | Respond to global needs |
Stress Concentration
Stress concentration is an important factor that affects product performance and safety. It tends to occur especially at shape changing points such as corners and holes, and can cause fatigue failure. It is necessary to identify locations where stress concentration is likely to occur at the design stage and take measures such as providing fillets (curved surfaces).
Heat Treatment
By applying heat treatment to aluminum die casting, strength and toughness can be improved. Heat treatment includes solution treatment and precipitation hardening, and it is necessary to select appropriate heat treatment according to the alloy type and required properties.
Surface Treatment
Corrosion resistance, wear resistance, and design can be improved by applying various surface treatments such as plating, polishing, chemical conversion, painting, and anodizing. Anodizing has the effect of increasing corrosion resistance and hardness, and is suitable for products used outdoors and products that require high durability.
Merits of Weight Reduction
Thinning and weight reduction contribute to reducing transportation costs and environmental impact. In automobile parts, etc., fuel efficiency improvement effect due to weight reduction can also be expected.
Realization of Complex Shapes
Die casting technology can integrally mold complex shapes, contributing to reducing the number of parts and assembly man-hours. This leads to product cost reduction and quality improvement.
Global Production Support
By establishing a system that enables production with the same quality not only in Japan but also at overseas bases, it is possible to respond to global needs.
By properly managing these other considerations, the quality, performance, cost, delivery time, and global responsiveness of aluminum die-cast products can be improved.
Summary
In aluminum die casting design, the balance of strength, accuracy, and thin-walledness is important. This article explains the know-how of material selection, structural design, CAE analysis, mold design, molding conditions, quality control, thin-walled design, etc. Quality assurance from the design stage is important, and high-quality, high-performance products can be manufactured efficiently by utilizing the latest technology. Aluminum die casting technology will continue to develop in the future, and we hope this article will be of help to everyone involved in design.
