Die casting is a versatile and efficient metal casting process used in various industries for producing high-quality, detailed parts. MRT Castings, with its expertise and state-of-the-art technology, offers the die casting methods needed for even the most complex projects. This blog explores the different types of die casting process available to OEMs and their unique advantages.
High pressure die casting: an in-depth look
High Pressure Die Casting is a widely used manufacturing process, especially well-suited for producing large volumes of complex, thin-walled parts. This method is particularly favoured in industries where precision, repeatability, and surface quality are paramount.
Let's delve deeper into the specifics…
PROCESS OVERVIEW
- Molten Metal Injection. In high pressure die casting, molten metal - typically aluminium - is injected under high pressure into a steel mold or die. This pressure is maintained until the metal solidifies.
- Die Construction. The dies are constructed of high-grade steel and consist of two halves. They are designed to withstand the high pressures of the process, often exceeding 30,000 psi.
- Ejection and Cooling. After solidification, the die halves are opened, and the casting is ejected. The die is then cooled before the next injection cycle begins.
Key Characteristics of High Pressure Die Casting
- Complex, Thin-walled Parts. High pressure die casting excels at producing parts with intricate geometries and thin walls, down to around
0.6 mm. This capability is unmatched by most other casting methods. - Excellent Dimensional Accuracy. The process offers exceptional dimensional accuracy and stability, making it suitable for parts requiring tight tolerances.
- Superior Surface Finish. High pressure die cast parts often require minimal surface finishing, thanks to the high quality of the surface straight from the die.
Technical Advantages
- High Speed and Efficiency. The cycle times in high pressure die casting are very short, often just a few seconds, allowing for the rapid production of a large number of parts.
- Automated Process. Much of the high pressure die casting process can be automated, further increasing efficiency and reducing labour costs.
- Material Economy. The high-pressure injection ensures efficient use of material, minimising waste.
Applications
- Automotive Industry. High pressure die casting is extensively used for producing components like engine blocks, gearbox cases, and other parts requiring high strength and precision.
- Consumer Electronics. Components for mobile devices, computers, and other electronics, where precision and miniaturisation are critical, are often made using high pressure die casting.
- Aerospace and Defence. Parts that demand lightweight and durability, such as brackets and housing, are frequently manufactured using this method.
Challenges and Considerations
- High Initial Investment. The cost of tooling for high pressure die casting can be substantial, making it more suitable for high-volume production to justify the initial expense.
- Porosity: While high pressure die casting produces parts with high density, porosity can be an issue, particularly in thicker sections. This requires careful design and process control.
In summary, high pressure die casting at MRT Castings offers a highly efficient, precise, and versatile method for producing high-quality, complex parts in large volumes. Its suitability for a wide range of metals, combined with its speed and efficiency, makes it a go-to choice for industries requiring precision and high throughout.
Gravity Die Casting: Detailed Overview
Gravity Die Casting is a casting process characterised by pouring molten metal into a permanent mold using gravity. This method is particularly effective for medium to high volume production of aluminium parts.
Here’s a more detailed look…
Process Details
- Mold Design and Construction. The molds used in gravity die casting are typically made of steel or iron and can be reused for several thousand cycles. The design of these molds is crucial for achieving the desired part geometry and surface finish.
- Pouring of Molten Metal. Unlike high pressure die casting, the molten metal in gravity die casting is poured into the mold without the aid of external pressure other than gravity. This leads to a slower filling process.
- Solidification and Ejection. After the molten metal is poured and allowed to fill the mold cavity, it cools and solidifies. The mold is then opened, and the solidified part is removed.
Advantages
- Dimensional Accuracy. Gravity die casting provides good dimensional accuracy, making it suitable for parts that require precise measurements but not as tight tolerances as high pressure die casting.
- Quality Surface Finish. The surface finish of gravity die cast parts is generally smoother than that of sand cast parts, reducing the need for additional surface finishing.
- Denser Castings. The slow pouring and solidification process allows for denser casting with fewer porosities compared to some other casting methods.
Technical Benefits
- Versatility in Size and Weight. Gravity die casting can produce parts ranging from small to fairly large sizes, offering flexibility in terms of part size and weight.
- Economic for Medium Volumes. The process is cost-effective for medium to high volume production runs, balancing mold cost with production efficiency.
- Material Efficiency. There is less material wastage in gravity die casting as compared to some other casting processes.
Applications
- Automotive Components. Gravity die casting is commonly used for making automotive parts such as engine components, gearbox cases, and wheel hubs.
- Electrical Fittings. This method is suitable for producing parts for electrical applications like housings and enclosures.
- General Engineering. Various engineering components that require a good surface finish and dimensional accuracy are often produced using gravity die casting.
Challenges and Limitations
- Mold Cost and Maintenance. While less expensive than high pressure die casting molds, gravity die casting molds still represent a significant investment and require maintenance.
- Not Best Suited for Very Thin Walls. Gravity die casting is less suited for extremely thin-walled or highly intricate parts due to the limitations of gravity in filling the mold.
- Porosity Management. While gravity die casting typically has fewer porosity issues than high pressure die casting, controlling porosity is still a critical aspect, especially for thicker sections.
In summary, gravity die casting at MRT Castings is an efficient, versatile process suitable for a range of applications. It combines good dimensional accuracy and surface finish with the economic benefits of medium to high volume production. While it doesn’t match the speed or intricacy achievable with high pressure die casting, it offers a balanced solution for many casting needs.
Low Pressure Die Casting: An Overview & Comparative Analysis 
Low pressure die casting is another method of metal casting, used predominantly for creating aluminium parts. Unlike the high pressure and gravity die casting methods offered by MRT Castings, this process is generally considered to be less precise, especially for highly detailed or thin-walled parts.
Process Description
- Controlled Pressure Application. In low pressure die casting, molten metal is pushed into the mold using a low, controlled pressure. This is in contrast to the high-pressure injection used in high pressure die casting.
- Die Design. The dies used are similar to those in gravity and high pressure die casting but are oriented differently to accommodate the pressure application from below.
- Cooling and Solidification. After the metal is injected into the die, it solidifies under pressure before being released.
Although suitable for medium complexity parts, low pressure die casting doesn't quite match the precision and ability to fill intricate molds that high pressure die casting offers. Also, compared to gravity die casting, it may produce parts with slightly less dimensional stability, particularly for very detailed designs.
Comparative Disadvantages
- Limited Material Options. Unlike the versatile material options available in high pressure and gravity die casting, low pressure die casting is generally limited to aluminium and its alloys.
- Reduced Complexity in Parts. While capable of producing good quality parts, low pressure die casting is not as effective as high pressure die casting in creating highly complex or thin-walled structures.
- Slower Production Speed. The cycle times for low pressure die casting are generally longer than high pressure die casting, making it less efficient for large-scale production.
- Lesser Dimensional Accuracy. Compared to high pressure die casting, this method may not achieve the same level of dimensional accuracy and stability, which is crucial for parts requiring tight tolerances.
Applications and Limitations
- Automotive and Aerospace. Low pressure die casting is used for components that do not require the intricate geometries or extreme precision that high pressure die casting provides.
- Cost Considerations. While the tooling costs might be lower than high pressure die casting, the overall production speed and efficiency are also lower, making it less economical for large volume production.
While low pressure die casting is a viable method for certain applications (particularly where moderate complexity and volume are involved), it does not offer the same level of precision, efficiency, and versatility as the high pressure and gravity die casting methods provided by MRT Castings. MRT chooses to focus on high pressure and gravity die casting as they better serve the needs of OEMs seeking high-quality, complex parts with faster production times and higher precision.
Die Casting Comparison
|
Die Casting Method
|
High Pressure Die Casting |
Gravity Die Casting |
Low Pressure Die Casting |
|
Volume Suitability |
High volume production |
Medium to high volume |
Medium volume production |
|
Surface Finish |
Excellent, with a smooth and detailed surface |
Good, with a smoother finish than low pressure die casting |
Good, but not as fine as high pressure or gravity die casting |
|
Dimensional Accuracy |
Very high, suitable for complex, thin-walled parts |
Good, suitable for parts requiring good dimensional stability |
Moderate, suitable for less complex designs |
|
Speed |
Very fast, efficient for large production runs |
Slower than high pressure, but still efficient |
Slow, best for small batches |
|
Complexity of Parts |
Suitable for complex, intricate designs |
Suitable for less complex parts than high pressure, but more than low pressure die casting |
Suitable for moderately complex designs, less so than high pressure and gravity die casting |
|
Materials Used |
Typically aluminium and zinc alloys |
Commonly aluminium and zinc alloys |
Mainly aluminium and its alloys |
|
Cost |
Higher initial tooling cost, but lower per-part cost in high volumes |
Lower tooling costs than high pressure, moderate per-part cost |
Lower initial tooling cost than high pressure, moderate per-part cost |
|
Ideal Applications |
Automotive, consumer electronics, and other industries needing large quantities of intricate parts |
Medium to large components in automotive, aerospace, and other industries |
Suitable for medium volume production without complex geometries |
MRT Castings offers a range of die casting methods, each with its own set of advantages, catering to diverse industrial needs. With MRT's expertise, clients can expect high-quality castings tailored to their specific requirements.
Starting a New Casting Project?
Read Our Guide, Notes for Designers of Non-Ferrous Castings
