Die casting is actually a metal casting method that is characterized by forcing molten metal under high-pressure in a mold cavity. The mold cavity is generated using two hardened tool steel dies which have been machined fit and work similarly to aluminum die casting parts along the way. Most die castings are made of non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin-based alloys. Based on the type of metal being cast, a hot- or cold-chamber machine is used.
The casting equipment as well as the metal dies represent large capital costs and this will 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 is especially suited for a big quantity of small- to medium-sized castings, which is why die casting produces more castings than almost every other casting process. Die castings are characterized by a very good surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, which is often used to remove gas porosity defects; and direct injection die casting, which is often used with zinc castings to reduce scrap and increase yield.
Die casting equipment was invented in 1838 with regards to producing movable type for the printing industry. The first die casting-related patent was granted in 1849 for any 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 had become the prominent form of equipment inside the publishing industry. The Soss die-casting machine, manufactured in Brooklyn, NY, was the 1st machine to get available in the open market in America. Other applications grew rapidly, with die casting facilitating the expansion of consumer goods and appliances by making affordable producing intricate parts in high volumes. In 1966, General Motors released the Acurad process.
The key die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting is additionally possible. Specific die casting alloys include: Zamak; zinc aluminium; die casting parts 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 easiest 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 those of steel parts.
Silicon tombac: high-strength alloy created from copper, zinc and silicon. Often used as a substitute for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; useful for special sorts 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 to the market and added further automation, with sometimes a large number of casting machines at one newspaper office.
There are a variety of geometric features to be considered when designing a parametric model of a die casting:
Draft is the volume of slope or taper provided to cores or some other aspects of the die cavity to permit for quick ejection in the casting from your die. All die cast surfaces that happen to be parallel for the opening direction in the die require draft for that proper ejection in the casting in the die. Die castings which include proper draft are easier to remove in the die and lead to high-quality surfaces plus more precise finished product.
Fillet is definitely the curved juncture of two surfaces that will have otherwise met with a sharp corner or edge. Simply, fillets might be put into a die casting to get rid of undesirable edges and corners.
Parting line represents the point from which two different sides of your mold get together. The location of the parting line defines which side of the die is the cover and the ejector.
Bosses are included with die castings to serve as stand-offs and mounting points for parts that should be mounted. For maximum integrity and strength in the die casting, bosses should have universal wall thickness.
Ribs are added to a die casting to provide added support for designs which need maximum strength without increased wall thickness.
Holes and windows require special consideration when die casting as the perimeters of the features will grip on the die steel during solidification. To counteract this affect, generous draft should be included with hole and window features.
The two main basic kinds of die casting machines: hot-chamber machines and cold-chamber machines. These are typically rated by how much clamping force they are able to apply. Typical ratings are between 400 and 4,000 st (2,500 and 25,400 kg).
Hot-chamber die casting
Schematic of the hot-chamber machine
Hot-chamber die casting, often known as gooseneck machines, depend on a swimming pool of molten metal to feed the die. At the outset of the cycle the piston of your machine is retracted, that enables the molten metal to fill the “gooseneck”. The pneumatic- or hydraulic-powered piston then forces this metal out of the die casting parts in the die. Some great benefits of this method include fast cycle times (approximately 15 cycles one minute) along with the comfort of melting the metal from the casting machine. The disadvantages of the system are that it must be limited by use with low-melting point metals and this aluminium cannot 21dexupky used mainly because it picks up a few of the iron whilst in the molten pool. Therefore, hot-chamber machines are primarily used in combination with zinc-, tin-, and lead-based alloys.
These are generally used once the casting alloy should not be employed in hot-chamber machines; these include aluminium, zinc alloys using a large composition of aluminium, magnesium and copper. This process for these particular machines get started with melting the metal inside a separate furnace. Then this precise volume of molten metal is transported towards the cold-chamber machine where it is actually fed into an unheated shot chamber (or injection cylinder). This shot will then be driven in to the die with a hydraulic or mechanical piston. The biggest disadvantage of this technique may be the slower cycle time as a result of need to transfer the molten metal from your furnace for the cold-chamber machine.