Die casting is actually a metal casting method that is described as forcing molten metal under high-pressure into a mold cavity. The mold cavity is produced using two hardened tool steel dies which were machined healthy and work similarly to CNC precision machining along the way. Most die castings are made of non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin-based alloys. According to the form of metal being cast, a hot- or cold-chamber machine can be used.
The casting equipment along with the metal dies represent large capital costs which has a tendency to limit the method to high-volume production. Production of parts using die casting is pretty simple, involving only four main steps, which will keep the incremental cost per item low. It really is especially suited for a big quantity of small- to medium-sized castings, which explains why die casting produces more castings than some other casting process. Die castings are observed as an excellent surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, which is used to eliminate gas porosity defects; and direct injection die casting, that is utilized with zinc castings to minimize scrap and increase yield.
Die casting equipment was invented in 1838 for the purpose of producing movable type for that printing industry. The very first die casting-related patent was granted in 1849 for any small hand-operated machine for the purpose of mechanized printing type production. In 1885 Otto Mergenthaler invented the linotype machine, an automated type-casting device which became the prominent form of equipment from the publishing industry. The Soss die-casting machine, made in Brooklyn, NY, was the first machine to get bought from the open market in The United States. Other applications grew rapidly, with die casting facilitating the increase of consumer goods and appliances through making affordable the production of intricate parts in high volumes. In 1966, General Motors released the Acurad process.
The principle die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting is likewise possible. Specific die casting alloys include: Zamak; zinc aluminium; aluminum die casting to, e.g. The Aluminum Association (AA) standards: AA 380, AA 384, AA 386, AA 390; and AZ91D magnesium.F This is a summary of the benefits of each alloy:
Zinc: the most convenient metal to cast; high ductility; high impact strength; easily plated; economical for small parts; promotes long die life.
Aluminium: lightweight; high dimensional stability for complex shapes and thin walls; good corrosion resistance; good mechanical properties; high thermal and electrical conductivity; retains strength at high temperatures.
Magnesium: the most convenient metal to machine; excellent strength-to-weight ratio; lightest alloy commonly die cast.
Copper: high hardness; high corrosion resistance; highest mechanical properties of alloys die cast; excellent wear resistance; excellent dimensional stability; strength approaching that relating to steel parts.
Silicon tombac: high-strength alloy created from copper, zinc and silicon. Often used as a replacement for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; employed for special forms of corrosion resistance. Such alloys are certainly not employed in foodservice applications for public health reasons. Type metal, an alloy of lead, tin and antimony (with sometimes traces of copper) is commonly used for casting hand-set type in letterpress printing and hot foil blocking. Traditionally cast in hand jerk moulds now predominantly die cast once the industrialisation of the type foundries. Around 1900 the slug casting machines came onto the market and added further automation, with sometimes a large number of casting machines at one newspaper office.
There are a number of geometric features to be considered when making a parametric style of a die casting:
Draft is the level of slope or taper given to cores or some other areas of the die cavity to permit for quick ejection from the casting from the die. All die cast surfaces which are parallel for the opening direction of your die require draft to the proper ejection from the casting through the die. Die castings that come with proper draft are easier to remove from your die and result in high-quality surfaces and more precise finished product.
Fillet is the curved juncture of two surfaces that might have otherwise met at a sharp corner or edge. Simply, fillets can be included with a die casting to get rid of undesirable edges and corners.
Parting line represents the point where two different sides of the mold come together. The location of the parting line defines which side of the die is the cover and which is the ejector.
Bosses are included in die castings to provide as stand-offs and mounting points for parts that should be mounted. For maximum integrity and strength of your die casting, bosses must have universal wall thickness.
Ribs are put into a die casting to offer added support for designs which need maximum strength without increased wall thickness.
Holes and windows require special consideration when die casting since the perimeters of the features will grip for the die steel during solidification. To counteract this affect, generous draft should be put into hole and window features.
The two main basic kinds of die casting machines: hot-chamber machines and cold-chamber machines. They are rated by simply how much clamping force they can apply. Typical ratings are between 400 and 4,000 st (2,500 and 25,400 kg).
Hot-chamber die casting
Schematic of any hot-chamber machine
Hot-chamber die casting, also known as gooseneck machines, rely upon a pool of molten metal to feed the die. At the start of the cycle the piston from the machine is retracted, allowing the molten metal to fill the “gooseneck”. The pneumatic- or hydraulic-powered piston then forces this metal out of your Zinc die casting to the die. Some great benefits of this technique include fast cycle times (approximately 15 cycles a minute) as well as the ease of melting the metal in the casting machine. The disadvantages of the system are that it is confined to use with low-melting point metals and therefore aluminium cannot 21dexupky used since it picks up several of the iron in the molten pool. Therefore, hot-chamber machines are primarily used in combination with zinc-, tin-, and lead-based alloys.
These are used when the casting alloy can not be utilized in hot-chamber machines; such as aluminium, zinc alloys using a large composition of aluminium, magnesium and copper. This process for such machines start out with melting the metal in the separate furnace. Then the precise quantity of molten metal is transported for the cold-chamber machine where it can be fed into an unheated shot chamber (or injection cylinder). This shot is then driven in to the die with a hydraulic or mechanical piston. The biggest problem with this technique will be the slower cycle time due to the must transfer the molten metal in the furnace towards the cold-chamber machine.