Die casting is a metal casting process that is described as forcing molten metal under high pressure right 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. Depending on the type of metal being cast, a hot- or cold-chamber machine is utilized.
The casting equipment and the metal dies represent large capital costs and also this will limit the procedure to high-volume production. Production of parts using die casting is fairly simple, involving only four main steps, which ensures you keep the incremental cost per item low. It is especially best for a sizable volume of small- to medium-sized castings, this is why die casting produces more castings than any other casting process. Die castings are observed as a very good surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, which is used to remove 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 when it comes to producing movable type for that printing industry. The very 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 form of equipment inside the publishing industry. The Soss die-casting machine, produced in Brooklyn, NY, was the 1st machine to be available in the open market in The United States. Other applications grew rapidly, with die casting facilitating the increase 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 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; 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 a summary 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 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 from steel parts.
Silicon tombac: high-strength alloy made of copper, zinc and silicon. Often used as an alternative for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; employed for special types of corrosion resistance. Such alloys usually are not found 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 enter letterpress printing and hot foil blocking. Traditionally cast at hand jerk moulds now predominantly die cast right after the industrialisation of your type foundries. Around 1900 the slug casting machines came on the market and added further automation, with sometimes lots of casting machines at one newspaper office.
There are numerous of geometric features that need considering when creating a parametric style of a die casting:
Draft is the quantity of slope or taper provided to cores or some other parts of the die cavity to enable for easy ejection of your casting from the die. All die cast surfaces that are parallel on the opening direction of the die require draft for the proper ejection of the casting from the die. Die castings that feature proper draft are simpler 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 would have otherwise met at the sharp corner or edge. Simply, fillets might be included with a die casting to eliminate undesirable edges and corners.
Parting line represents the purpose at which two different sides of a mold get together. The location of the parting line defines which side of your die may be the cover and the ejector.
Bosses are put into 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 must have universal wall thickness.
Ribs are included in a die casting to deliver added support for designs that need maximum strength without increased wall thickness.
Holes and windows require special consideration when die casting as the perimeters of these features will grip towards the die steel during solidification. To counteract this affect, generous draft must be included in hole and window features.
There are two basic types of die casting machines: hot-chamber machines and cold-chamber machines. These are generally rated by just how much clamping force they could 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 referred to 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, that enables the molten metal to fill the “gooseneck”. The pneumatic- or hydraulic-powered piston then forces this metal out from the Zinc die casting into the die. The benefits of this system include fast cycle times (approximately 15 cycles a minute) and also the ease of melting the metal from the casting machine. The disadvantages with this system are that it is confined to use with low-melting point metals which aluminium cannot 21dexupky used as it picks up a few of the iron whilst in the molten pool. Therefore, hot-chamber machines are primarily used with zinc-, tin-, and lead-based alloys.
These are used once the casting alloy should not be used in hot-chamber machines; some examples are aluminium, zinc alloys by using a large composition of aluminium, magnesium and copper. The procedure for such machines start with melting the metal within a separate furnace. Then the precise amount 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 in the die by way of a hydraulic or mechanical piston. The greatest problem with this system may be the slower cycle time due to the need to transfer the molten metal through the furnace for the cold-chamber machine.