Introduction of die casting (High-Pressure Die Casting)
What is die casting?
Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminum, magnesium, lead, pewter, and tin-based alloys.
There are two main types of die casting machines – hot chamber machines (used for alloys with low melting temperatures, such as zinc) and cold chamber machines (used for alloys with high melting temperatures, such as aluminum).However, in both machines, after the molten metal is injected into the dies, it rapidly cools and solidifies into the final part, called the casting.
Die casting can have significant advantages over other manufacturing processes, which often lead to major cost savings, not only in the part price itself but also in the overall cost of production. When you cast a part, you can create complex net shapes, including external threads and complex internal features with minimal draft angles—minimizing secondary operations. You can also combine multiple parts into a single part, eliminating assembly operations and lowering labor costs, with the added benefits of simplified stock control and greater component consistency.
The advantages and disadvantages of die casting
- Excellent dimensional accuracy (dependent on casting material, but typically 0.1 mm for the first 2.5 cm (0.004 inch for the first inch) and 0.02 mm for each additional centimeter (0.002 inch for each additional inch).
- Smooth cast surfaces (Ra 1–2.5 micrometers or 0.04–0.10 thou rms).
- Thinner walls can be cast as compared to sand and permanent mold casting (approximately 0.75 mm or 0.030 in).
- Inserts can be cast-in (such as threaded inserts, heating elements, and high strength bearing surfaces).
- Reduces or eliminates secondary machining operations.
- Rapid production rates.
- Casting tensile strengthas high as 415 megapascals (60 ksi).
- Casting of low fluidity metals.
- High capital cost
- A large production volume is needed.
- Limited to high-fluidity metals
- Casting weights must be between 30 grams (1 oz) and 10 kg (20 lb).
- Prevents any heat treating or welding
- Parts needing hardeningand tempering are not cast in dies.
The Process of die casting
- Preparing the Mold
The first step of high-pressure die casting is mold preparation. During this initial step, the manufacturing company applies a lubricant to the interior walls of the mold. This is important because the lubricant regulates the mold’s temperature while also creating a film between the molten metal and the mold, thereby allowing for easier removal of the casting.
After preparing the die mold, the manufacturing company injects it with molten metal. The mold must be completed closed and sealed during this step. Otherwise, it won’t be able to “accept” the highly pressurized molten metal. Depending on the specific application, the molten metal may be injected into the mold at a pressure of between 1,500 to 25,000 pounds per square inch (PSI). The mold maintains this pressure until the molten metal has cooled and solidified.
- Cavity Ejection
Next, the manufacturing company ejects the newly made cavity from the mold. The mold itself typically features ejector pins that, when engaged, release the cavity. Of course, the cavity must be solid for it to eject. If the raw metal is still liquid, the manufacturing company must wait for it to cool before it can eject the cavity from the mold.
The fourth and final step of high-pressure die casting is shakeout. During this step, the manufacturing company separates any scrap metal from the newly created cavity. It’s not uncommon for high-pressure die casting to produce excess scrap metal. In other words, not all of the molten metal is used to create the casting. Some remains stuck inside the mold. As a result, the scrap metal must be removed before the mold can be reused.
To recap, high-pressure die casting generally consists of four steps: preparing the mold, injecting the mold with molten metal, ejecting the newly created cavity from the mold, and separating scrap metal from the cavity.
The application of die casting
Die casting is mainly used for large series production, i.e. for many components of the same type to be cast. Despite the high pressure used during the manufacturing process, a high casting quality is achieved. The die casting process is particularly suitable to produce very thin (up to 1 mm) (lightweight) components.
Most commonly, die cast components are manufactured for the automotive industry, such as wheels, blocks, cylinder heads, valve blocks and manifolds. The use of aluminum parts leads to a reduction in the weight of the vehicles and thus to a reduction in fuel consumption. In addition, there are other industries in which die cast parts are used:
- Domestic Appliances
- Power Tools
- Lighting Technology
What can we do die casting for you?
Die casting is a very effective manufacturing process to produce parts that have accurate dimensions and sharp definition in large quantities, made possible using reusable metal dies.
- Product size: as customer’s required
- Material available: aluminum, zinc, etc.
- Tolerance: normally UNI-ISO 2768, etc.
- Surface treatment: Zn-plating, Cr-plating, powder coating, electro-deposition, etc.
- Packing: as per customers’ requirement
- Measurement: 2.5D Projecting apparatus, Altimeter, Calipers, Coating thickness tester
- Application: as customer’s required
To know more about die casting parts, please feel free to contact us. We can base your drawings to give more advise about which manufacturing process is better, and how to do it.
To know more about Casting or Diecasting process, please see here – https://www.machinemfg.com/types-of-casting/