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Aluminium Die Casting - An Efficient Manufacturing Process for Precision Metal Parts
Aluminium die casting is a popular manufacturing process used to produce high-quality metal parts and components with excellent dimensional accuracy and surface finish. In this process, molten aluminium alloy is injected with high pressure into reusable steel moulds, called dies. Once the molten metal solidifies, the die is opened and the casting is ejected. Aluminium is commonly used for die casting due to its lightweight, corrosion resistance, high ductility, electrical conductivity and ability to be cast into complex shapes.
Die casting offers several advantages over other manufacturing processes. It is extremely efficient at producing large volumes of complex, thin-walled aluminium parts with fine details and tight tolerances. The fast production rates, low labour costs and consistency in the die casting process results in very economical manufacturing, especially for large runs. Minimal secondary machining is required as the castings have excellent surface finish straight out of the die. Even the most complex geometry with hidden forms, slots, threads, and holes can be easily cast to tight tolerances. Die cast parts have excellent repeatability which allows for interchangeability between castings from multiple die cavities or tooling of the same design. Given these benefits, die casting is ideal for high-volume production and is commonly used across various industries such as automotive, aerospace, medical, industrial machinery and consumer products.
The Die Casting Process
Aluminium die casting involves just four major steps after the initial die design and construction:
1. Clamping - The two halves of the die tool, made from tool steel, are clamped together and securely locked. The injected molten metal is forced into the die cavity between the opened halves during this closed die process.
2. Injection - Molten aluminium at temperatures between 650 to 800 °C is injected into the die cavity with high pressure of around 10 to 150 MPa from the holding furnace through gooseneck ladles. The entire cavity is filled in less than 50 milliseconds.
3. Cooling - The die halves are cooled internally with water circulating through cooling lines surrounding the cavity. This causes the molten metal to rapidly solidify into the desired shape against the die walls in about 40 to 90 seconds.
4. Ejection - Once fully solidified and cooled, the die halves separate and the casting is ejected using ejector pins. The casting will be near room temperature at this point.
After removal any runners, overflows and flash are cut off the casting and it undergoes post-processing which may involve heat treatment, surface finishing, polishing, powder coating, plating, assembly or other secondary operations. The reusable die can then be cleaned, sprayed and clamped shut again for the next cycle. An experienced die caster can produce around 45,000 aluminium die castings a day from a single die.
Popular Alloys for Die Casting
The most commonly used aluminium alloys for die casting include:
- Aluminum 383 - Offers excellent corrosion resistance, ductility and strength. Used for housings, covers, cylinders, and marine components.
- Aluminum 360 - Machinable alloy with good strength and ductility. Used for parts requiring good bearing properties such as gears and bushings.
- Aluminum 413 - Free machining alloy with improved chip breaking over 383 and 360. Used for high strength components requiring machining.
- Aluminum 518 - Alloy with excellent creep resistance, tensile properties and pressure tightness. Used for parts exposed to high temperatures like vehicle engine parts.
The selected alloy depends on the required part properties, performance requirements, corrosion resistance needed and machining characteristics. Other factors are die casting tolerances needed, casting wall thickness, complexity of die casting shape and production volumes.
Design Considerations for Die Cast Parts
Aluminium die casting enables manufacture of stronger and lighter components not feasible through other methods. To fully utilize the benefits of the process, the part must be properly designed for die casting. Here are some of the design considerations:
- Avoiding sharp corners and edges helps proper metal flow in the die. Internal radiused corners greatly improve casting quality.
- Uniform wall thickness throughout the part should be maintained as much as possible to prevent premature solidification. Sudden wall thickness changes can trap gases creating porosity.
- Draft angles of at least 1 to 3 degrees should be added on vertical surfaces to allow for easy part ejection from the die tool.
- Proper placement of parting lines, ejector pin locations and overflow runners enables complete cavity filling and avoids defects in cast parts.
- Aluminium die casting can produce section thickness from 0.5 to 9 mm. The section with greatest mass should be placed furthest from die opening to prevent early solidification.
- Gates and runners should be smoothly tapered, rounded and streamlined to facilitate clean filling without turbulence.
- Avoid hollow sections in castings since they cannot be inspected visually. Hollow sections should have a minimum thickness of 3 mm.
- Avoid bosses as they act as heat sinks creating hot spots. When required, bosses must have proper gussets and fillets to avoid cracking.
Die casting enables consolidating multiple parts into one complex component. Following proper design rules results in high quality aluminium die cast parts.
Common Aluminium Die Casting Defects
Some common defects found in aluminium die castings are:
- Porosity - Entrapped gas voids in the casting due to fast cooling.
- Cold laps - Unmelted metal along fused surfaces caused by low metal temperature or early freezing.
- Hot tears - Intergranular failure due to stresses from hindered contraction while solidifying.
- Shrinkage cavities - Depression in surface due to volume contraction on cooling.
- Soldering/Erosion - Damage of die surface from washing effect of molten metal.
- Sticking - Casting sticking to die walls instead of clean ejection.
- Warping - Non uniform cooling causing stresses and distorted castings.
Robust process control is critical for avoiding defects in aluminium die cast parts. Use of quality materials, maintaining die temperature, vacuum assistance, suitable gating, controlled shot speeds andised inspection are methods to prevent defects. Secondary operations may be required to eliminate defects affecting appearance or performance.
Trends in Aluminium Die Casting
Recent years have seen significant advancements in aluminium die casting technologies. Some of the trends shaping the industry are:
- Increased automation through robotics and digitalization for quality improvements and efficient production.
- Vacuum die casting providing porosity-free castings through reduced air entrapment.
- Multi-slide die casting allowing multiple plungers in the same die for higher output.
- Progress in die materials like steel alloys, coatings and heat treatments enhancing die life and precision.
- Simulation software helps optimize die design, achieve defect-free castings and reduce lead time.
- Rapid tooling like 3D printing adopted for prototype and low volume castings before mass production tooling.
- Closed loop monitoring via sensors and AI to self-correct deviations in real-time die casting processes.
- Focus on sustainable solutions like recycling, lightweighting and waste reduction.
- Usage of recycled aluminium and higher recycled content alloys.
Aluminium die casting continues to expand into new markets with its design flexibility, quality and cost-effectiveness. Integration of the latest technologies increases process efficiency, energy savings, minimizes defects and enables just-in-time production.
Leading Aluminium Die Casting Companies
Some of the renowned aluminium die casting manufacturers across the world include:
- Shiloh Industries - Leading global supplier of lightweighting solutions for automotive, commercial vehicles, aerospace, defense and industrial markets.
- Georg Fischer - Large machining, die casting and packaging technologies provider based in Switzerland.
- Alcast Technologies - Canadian company offering tooling, machining and assembly services along with die casting.
- Ryobi Die Casting - Japanese die caster specializing in high quality, slim and complex aluminium die castings.
- Endurance Technologies - Major Indian auto component manufacturer including aluminium die casting parts.
- Guangdong Hongtu - China's largest export-oriented die casting company with customers worldwide.
- Rockman Industries - Top Indian two-wheeler component manufacturer with focus on aluminium die casting parts.
- Bühler Group - Global technology company and leading supplier of die casting equipment and solutions.
- Cast Products Inc - American high volume aluminium die caster with over 50 years of experience.
- Premier Die Casting - UK based low, medium and high volume die casting supplier for various industries.
These leading die casters utilize the latest equipment, software and quality processes to deliver high precision, complex cast aluminium components. With enhanced capabilities and automation, they can meet rising demands across diverse sectors reliably and cost-effectively.
Conclusion
Aluminium die casting facilitates economical, high-volume production of precision, net-shape metal parts. It helps manufacture lightweight, durable and high-performance components from aluminium alloys for diverse applications across industries. Die cast aluminium sees expanding use in automobiles, electrical, telecom, defense and healthcare sectors owing to its strength, corrosion resistance and ability to form complex shapes. With constant developments in die casting technology, processes and alloys, the applications and capabilities continue to grow further. Reputed die casters with automated operations, stringent quality control and experience ensure delivery of flawless castings from prototype to mass production volumes. CNC Milling CNC Machining