Die Castings

About Die Castings and Die Casting Manufacturers Including: Aluminum Castings, Aluminum Die Castings, Die Casters, Metal Castings & Zinc Die Castings.

Die casting is a metal forming process in which molten metal is forced into mold cavities, or dies, under high pressure then cooled in order to form solid metal parts. Facilities where die castings are made are referred to as foundries. Die cast parts are typically made from non-ferrous metals such as zinc, aluminum, copper, magnesium, lead, tin and bronze; alloy tool steels may be formed through die casting as well, although the preferred fabrication method for steel parts is forging. For many years, die castings have presented a cost-effective and highly versatile alternative to more traditional methods such as forging and hand tooling. Die cast parts are capable of reaching much closer tolerances and far more complex shapes than forgings or stamped metals while requiring minimal secondary tooling and processing. Die casters can manufacture large quantities of aluminum die castings, zinc die castings and other metal castings with good detail, surface quality and dimensional consistency at relatively low cost.

Because complex parts can be die cast at high volume, many manufacturing industries use die cast parts both in their products and equipment. Before the advent of vacuum formed and injection molded plastics, die cast parts provided the exterior shape of many common products and consumer items, such as cash registers and parking meters. Many modern parts which require the strength of metal still use whole die cast parts, such as gumball machine bases, sink faucets, gas pump handles and an exhaustive range of metal parts used in automotive and industrial machinery. Computer and electronics industries use high tolerance magnesium die castings as housings and interior EMI enclosures as well as miniature zinc die cast parts for various electronic equipment applications.

Before parts can be cast, a cavity must be tooled into the desired shape of the part. For closed die castings, which are the majority of castings, this cavity is cut into in two separate metal blocks; in order to form a complete mold, the tooled blocks are placed together with cavities aligned. This cavity is called a die. Once the die has been created, it is sprayed with a lubricant which helps control the die's temperature and assists in part removal once the cast is complete. The die is then closed, and molten metal is poured into the shot sleeve and injected into the die under high pressure by a plunger. Pressure is maintained within the die until the cast has solidified, then the die is opened and ejector pins push out the solidified "shot". This metal piece considered a shot until the excess material which has solidified around the casting is removed. This excess material typically consists of sprue, gate, runners and flash which have formed in channels leading to the die mold and possibly in leakage areas between the mold cavities. The cast part is tooled and deburred to remove this excess and is sometimes put through additional secondary processes such as surface finishing, plating and CNC machining.

Die casting is a high volume, low cost means of forming relatively complex metal parts. Because this forming method does not create a uniform molecular structure or grainflow as forging and extruding processes do, die cast parts do not have high strength and often have microfractures and grainflow inconsistencies which can lead to part failure or breakage under strain, corrosion or heat stress. For this reason, die cast parts are often heat-treated and carefully tested after manufacturing, but critical applications requiring high strength, high resistance parts use forgings rather than die castings. Although the die casting process is not capable of manufacturing high strength, high resistance parts, die cast parts can reach far greater complexities with much higher tolerances than any other metal forming process. In recent years, some traditionally die cast parts which do not require the strength of metal have been replaced with plastic injection molded parts due to plastic's lower cost and lighter weight.

Die Castings and Die Casting Manufacturers Image Provided by Crown Die Casting Corporation

Die Casting Types

• Aluminum castings are die castings made from aluminum materials.
• Aluminum die castings are commonly used in the production of hardware and tools because of the great resistance of aluminum castings to corrosion and high temperatures, as well as their conductivity. In addition, aluminum castings are used in applications requiring the production of intricate part features and components.
  
• Automotive castings, which include engine blocks, cylinder heads, brake calipers and discs and suspension components, are increasingly being manufactured out of lightweight material, such as aluminum, to economize fuel consumption by decreasing the overall weight of the vehicle.
  
• Brass castings are used in the architectural and construction industries and in decorative applications, such as doorknobs.
  
• Bronze castings are used in applications requiring high strength, making them ideal for use in the architectural and construction industries.
  
• Copper die castings are used in applications requiring exceptional strength and resistance to corrosion. Copper castings consist of brass and bronze castings.
  
• Die casters shape metal by putting pressure on molten metal in a die.
• Gravity die castings are produced by pouring molten aluminum into a metallic tool at a casting temperature of 750˜. Gravity die castings have good tolerances and surface finishing.
  
• High pressure die castings have very thin walls. The metal enters the die cavity at high speeds and under great pressure, which increases the chance of porosity.
  
• Lead die castings offer great corrosion resistance and are used in the production of parts in the plumbing industry. Lead castings, particularly tin castings, also provide close production tolerances but are generally not as strong as other diecast metals.
  
• Low pressure die castings are formed when metal from an airtight furnace is transferred into a metallic tool through a rising tube. Low pressure die casting is suitable for relatively small lot sizes and for applications in which heat treatment is needed to improve the mechanical properties.
  
• Magnesium die castings are particularly useful in applications where weight is a factor. Magnesium die castings are very lightweight and cost-effective, especially in comparison to other diecast metals.
  
• Metal castings are metal impressions made with molds.
• Zinc die castings are often used in the production of small parts for the electronics and automotive industries. Zinc castings lend themselves well to secondary operations such as painting and plating.

Die Casting Terms

Automation - Industry term commonly used to describe the mechanization of various aspects of die casting process.

Biscuit - An excess of molten metal that is leftover in the shot sleeve of a cold chamber die casting machine. Biscuits are considered part of the cast shot and are removed from the die with the casting. 

Blister - Die casting deformation consisting of a gaseous bubble on the surface of the casting and a hole in the casting underneath the bubble. 

Blow holes - Voids or pores which may occur due to entrapped gas or shrinkage during solidification, usually evident in heavy sections. (See porosity)

Cavity - The recess or impressions in a die in which the casting is formed.

Cold chamber machine - A type of die casting machine in which the metal injection mechanism is not submerged in molten metal.

Checking - Fine cracks on the surface a die which produce corresponding raised veins on die casting. Caused by repeated heating of the die surface by injected molten alloys. Also called heat checking.

Die lubricants - Liquid formulations applied to the die to facilitate casting release and prevent soldering.

Dimensional stability - Ability of a component to retain it`s shape and size over a long period of service.

Draft - The taper given to walls, cores and other parts of the die cavity to permit easy ejection of the casting.

Ejector marks - Marks left on castings by ejector pins.

Ejector pins - A rod which forces the casting out of the die cavity and off cores.

Ejector plate - A plate that actuates the ejector pins attached to it. 

Fillet - Curved junction of two surfaces, e.g., walls which would meet a sharp angle.

Flash - Excess metal on a die cast part extending past the parting line of the die set, which blocks metal from flowing past the die lines and filling the die impressions. 

Gate - Passage for molten metal which connects runner with die cavity. Also, the entire ejected content of a die, including castings, gates, runners sprue (or biscuit) and flash.

Growth - Expansion of a casting as a result of aging or of intergranular corrosion, or both.

Heat checking - (See checking)

Hot chamber machine - Die casting machine in which the pressure chamber is subjected to the molten metal through immersion. Hot chamber machines are used in the die casting of metals with low melting points, such as zinc die casting, copper die casting and magnesium die casting.

Impact strength - Ability to resist shock, as measured by a suitable testing machine.

Ingot - Metal or alloy cast in a convenient shape for storage shipping or remelting.

Injection - The processes of forcing molten metal into a die.

Insert - A piece of material, usually metal, which is placed in a die before each shot. Molten metal is cast around it to produce certain features on and within the die cast part.

Loose piece, knockout - A type of core (which forms undercuts) which is positioned in, but not fastened to a die. It is so arranged as to be ejected with the casting and from which it is removed. It is repeated for the same purpose.

Metal saver - Core utilized to prevent sections of excessive thickness from occurring and to reduce the amount of metal used in a metal casting.

Multiple cavity die - A die having more than one duplicate impression.

Overflow - An opening or cavity on the parting line of the die outside of the main die cavity into which unacceptable metal flows during the shot process. Reasons for metal unacceptability include improperly heated metal and metal that contains impurities.

Parting line - A line along the surface of a die casting reflecting the small space between the die halves; also, the mating surface of the cover and ejector portions of the die.

Plunger - Ram or piston which forces molten metal into a die.

Porosity - Very small voids or pores in cast metal parts resulting from trapped gas, or shrinkage during solidification.

Process control - Where parameters of a process are studied and correctly applied in the manufacturing process to produce high quality parts.

Runners - Horizontal mechanisms connected to the sprue that transfers the molten metal from the sprue to the mold.

Shot - The process in which the metal is poured into the die. The shot may also refer to the die cast part as it exists as a cast before secondary operations are performed to remove flash and to fix imperfections in the casting.

Shrinkage, solidification - Dimensional reduction that accompanies the freezing (solidification) of metal, passing from the molten to the solid state.

Shrink mark - A surface depression which sometimes occurs next to a heavy section that cools more slowly than adjacent areas.

Slide - The portion of a die arranged to move parallel to die parting. The inner and end forms a part of the die cavity wall that involves one or more undercuts and sometimes includes a core or cores.

Soldering - Adherence of molten metal to portion of the die.

Sprue - Mechanism with which the molten metal first makes contact during the shot process. The sprue transfers the molten metal to the runners.

Trim die - A die for shearing or shaving flash from a die casting.

Trim - The process in which overflow, flash and other parts are removed from the die cast part or shot.

Unit die - A die interchangeable with others in a common holder.

Undercut - Recess in the side wall or cored hole of a casting disposed so that a slide or special form of core (such as a knockout) is required to permit ejection of the casting from the die.

Vent - An orifice in the casting die that facilitates the release of air from the die cavity into the atmosphere to prevent casting imperfections, such as porosity.

Void - A large pore or hole within the wall of a casting usually caused by entrapped gas. A blow hole.

Waterline - The channel in the casting die into which water flows to precipitate the cooling of the die casting.