Die casting can be a metal casting process 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 has been machined into shape and work similarly to CNC precision machining during the process. Most die castings are manufactured from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin-based alloys. Dependant upon the type of metal being cast, a hot- or cold-chamber machine can be used.
The casting equipment and the metal dies represent large capital costs and this tends to limit the method to high-volume production. Production of parts using die casting is comparatively simple, involving only four main steps, which keeps the incremental cost per item low. It is especially best for a large amount of small- to medium-sized castings, this is why die casting produces more castings than any other casting process. Die castings are seen as a a very good surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, which is often used to reduce gas porosity defects; and direct injection die casting, which is used with zinc castings to minimize scrap and increase yield.
Die casting equipment was invented in 1838 for the purpose of producing movable type for your printing industry. The first die casting-related patent was granted in 1849 for a small hand-operated machine when it comes to mechanized printing type production. In 1885 Otto Mergenthaler invented the linotype machine, an automated type-casting device which became the prominent type of equipment from the publishing industry. The Soss die-casting machine, made in Brooklyn, NY, was the very first machine to become sold in the open market in The United States. Other applications grew rapidly, with die casting facilitating the expansion of consumer goods and appliances if you make affordable the production of intricate parts in high volumes. In 1966, General Motors released the Acurad process.
The main 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 The following is an overview of the advantages 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 easiest 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 manufactured from copper, zinc and silicon. Often used as an alternative for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; utilized for special kinds of corrosion resistance. Such alloys are certainly not utilized in foodservice applications for public health reasons. Type metal, an alloy of lead, tin and antimony (with sometimes traces of copper) is used for casting hand-set enter letterpress printing and hot foil blocking. Traditionally cast at hand jerk moulds now predominantly die cast once the industrialisation of your type foundries. Around 1900 the slug casting machines came into the market and added further automation, with sometimes dozens of casting machines at one newspaper office.
There are numerous of geometric features that need considering when designing a parametric model of a die casting:
Draft is the volume of slope or taper made available to cores or some other elements of the die cavity to allow for convenient ejection in the casting through the die. All die cast surfaces which are parallel on the opening direction from the die require draft to the proper ejection of the casting from the die. Die castings which include proper draft are easier to remove from your die and cause high-quality surfaces plus more precise finished product.
Fillet will be the curved juncture of two surfaces that might have otherwise met with a sharp corner or edge. Simply, fillets could be included with a die casting to get rid of undesirable edges and corners.
Parting line represents the point from which two different sides of a mold combine. The location of the parting line defines which side of the die will be the cover and the ejector.
Bosses are included with die castings to serve as stand-offs and mounting points for parts that will need to be mounted. For optimum integrity and strength of your die casting, bosses will need to have universal wall thickness.
Ribs are included with a die casting to supply added support for designs that require maximum strength without increased wall thickness.
Holes and windows require special consideration when die casting for the reason that perimeters of such features will grip to the die steel during solidification. To counteract this affect, generous draft should be included in hole and window features.
There are 2 basic types of die casting machines: hot-chamber machines and cold-chamber machines. They are rated by 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 a hot-chamber machine
Hot-chamber die casting, also referred to as gooseneck machines, depend on a pool of molten metal to give the die. At the start of the cycle the piston from the machine is retracted, that allows 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 method include fast cycle times (approximately 15 cycles one minute) and the comfort of melting the metal in the casting machine. The disadvantages of this system are that it is limited to use with low-melting point metals and this aluminium cannot 21dexupky used since it picks up several of the iron whilst in the molten pool. Therefore, hot-chamber machines are primarily combined with zinc-, tin-, and lead-based alloys.
These are used when the casting alloy can not be used in hot-chamber machines; such as aluminium, zinc alloys with a large composition of aluminium, magnesium and copper. The process for these particular machines get started with melting the metal in the separate furnace. A precise amount of molten metal is transported for the cold-chamber machine where it really is fed into an unheated shot chamber (or injection cylinder). This shot will be driven in to the die from a hydraulic or mechanical piston. The largest disadvantage of this method may be the slower cycle time due to must transfer the molten metal from the furnace to the cold-chamber machine.