Die casting is actually a metal casting procedure that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is produced using two hardened tool steel dies that have been machined fit and work similarly to aluminum die casting parts during the process. Most die castings are manufactured from 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 is commonly used.
The casting equipment as well as the metal dies represent large capital costs and this tends to limit this process to high-volume production. Manufacture of parts using die casting is relatively simple, involving only four main steps, which keeps the incremental cost per item low. It can be especially best for a huge quantity of small- to medium-sized castings, which is the reason die casting produces more castings than almost every other casting process. Die castings are seen as a a good surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, that is utilized to eliminate gas porosity defects; and direct injection die casting, which is used with zinc castings to reduce scrap and increase yield.
Die casting equipment was invented in 1838 just for producing movable type for your printing industry. The initial die casting-related patent was granted in 1849 for the small hand-operated machine just for mechanized printing type production. In 1885 Otto Mergenthaler invented the linotype machine, a computerized type-casting device which had become the prominent sort of equipment inside the publishing industry. The Soss die-casting machine, produced in Brooklyn, NY, was the very first machine to become bought from the open market in Canada And America. Other applications grew rapidly, with die casting facilitating the expansion of consumer goods and appliances simply by making affordable producing 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 additionally 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 benefits of each alloy:
Zinc: the best 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 of 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; utilized for special forms of corrosion resistance. Such alloys are not used in foodservice applications for public health reasons. Type metal, an alloy of lead, tin and antimony (with sometimes traces of copper) can be used for casting hand-set type letterpress printing and hot foil blocking. Traditionally cast in hand jerk moulds now predominantly die cast after the industrialisation from the type foundries. Around 1900 the slug casting machines came on the market and added further automation, with sometimes dozens of casting machines at one newspaper office.
There are a number of geometric features that need considering when making a parametric style of a die casting:
Draft is the level of slope or taper provided to cores or other parts of the die cavity to allow for easy ejection in the casting through the die. All die cast surfaces which can be parallel to the opening direction of the die require draft for that proper ejection from the casting from the die. Die castings which feature proper draft are easier to remove through the die and cause high-quality surfaces and more precise finished product.
Fillet may be the curved juncture of two surfaces that will have otherwise met with a sharp corner or edge. Simply, fillets might be included in a die casting to remove undesirable edges and corners.
Parting line represents the purpose in which two different sides of the mold get together. The location of the parting line defines which side of the die is the cover and which is the ejector.
Bosses are put into die castings to serve as stand-offs and mounting points for parts that will have to be mounted. For maximum integrity and strength of your die casting, bosses need to have universal wall thickness.
Ribs are included with 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 those features will grip to the die steel during solidification. To counteract this affect, generous draft should be put into hole and window features.
The two main basic forms of die casting machines: hot-chamber machines and cold-chamber machines. These are generally rated by exactly 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 the hot-chamber machine
Hot-chamber die casting, also called gooseneck machines, depend on a swimming pool of molten metal to give the die. At the start of the cycle the piston of your machine is retracted, that allows the molten metal to fill the “gooseneck”. The pneumatic- or hydraulic-powered piston then forces this metal out from the Zinc die casting in the die. The benefits of this product include fast cycle times (approximately 15 cycles a minute) and also the ease of melting the metal within the casting machine. The disadvantages with this system are that it is limited to use with low-melting point metals and this aluminium cannot 21dexupky used since it picks up a number of the iron in the molten pool. Therefore, hot-chamber machines are primarily combined with zinc-, tin-, and lead-based alloys.
These are typically used once the casting alloy should not be employed in hot-chamber machines; some examples are aluminium, zinc alloys with a large composition of aluminium, magnesium and copper. The method for such machines get started with melting the metal within a separate furnace. A precise level of molten metal is transported to the cold-chamber machine where it is actually fed into an unheated shot chamber (or injection cylinder). This shot is going to be driven to the die by way of a hydraulic or mechanical piston. The greatest downside of this method is the slower cycle time due to the need to transfer the molten metal through the furnace towards the cold-chamber machine.