Die Casting’s Blog

Aluminum Die Casting leverages our experience in aluminum die castings, precision machining, assembly and program management philosophy in providing our customers with industry leading solutions.

Automation

Die Cast, with our commitment to continuous improvement, is currently 85% automated and will be 89% automated by the end of 2005. We continue to implement process automation enhancements.

Aluminum Die Casting Rimrock automation equipment:

Auto Ladle
Auto Spray
Auto Extract
Shot Monitoring
Automatic plunger lube application
Trim unloading

Process and work flow improvements including:

Special machines for high volume repetitive products.
Dedicated Work cells.
Cellular automation.
Trim stations/secondary operations at die cast machines.
Packaging at trim stations.
Part Conveying Systems.
Automation offers:

Improved quality through consistent processing.
Better equipment utilization.
Higher productivity with reduced labor.
Cleaner work environment.
Improved Morale.

Die-casting is similar to Permanent mold castings except that the metal is injected into the mold under high pressure of 10-210Mpa (1,450-30,500) psi . This results in a more uniform part, generally good surface finish and good dimensional accuracy, as good as 0.2 % of casting dimension. For many parts, post-machining can be totally eliminated, or very light machining may be required to bring dimensions to size.

Die-casting can be done using a cold chamber or   hot chamber process

1.In a cold chamber process, the molten metal is ladled into the cold chamber for each shot. There is less time exposure of the melt to the plunger walls or the plunger. This is particularly useful for metals such as Aluminum, and Copper (and its alloys) that alloy easily with Iron at the higher temperatures.

2.In a hot chamber process the pressure chamber is connected to the die cavity is immersed permanently in the molten metal. The inlet port of the pressurizing cylinder is uncovered as the plunger moves to the open (unpressurized) position. This allows a new charge of molten metal to fill the cavity and thus can fill the cavity faster than the cold chamber process. The hot chamber process is used for metals of low melting point and high fluidity such as tin, zinc, and lead that tend not to alloy easily with steel at their melt temperatures.

Die casting molds (called dies in the industry) tend to be expensive as they are made from hardened steel-also the cycle time for building these tend to be long. Also the stronger and harder metals such as iron and steel cannot be die-cast

Common Alloys in Die Casting

Aluminum, Zinc and Copper alloys are the materials predominantly used in die-casting. On the other hand, pure Aluminum is rarely cast due to high shrinkage, and susceptibility to hot cracking. It is alloyed with Silicon, which increases melt fluidity, reduces machinability. Copper is another alloying element, which increases hardness, reduces ductility, and reduces corrosion resistance.

Aluminum is cast at a temperature of 650 ºC (1200 ºF). It is alloyed with Silicon 9% and Copper about 3.5% to form the Aluminum Association 380 alloy (UNS A03800). Silicon increases the melt fluidity, reduces machinability, Copper increases hardness and reduces the ductility. By greatly reducing the amount of Copper (less than 0.6%) the chemical resistance is improved; thus, AA 360 (UNS A03600) is formulated for use in marine environments. A high silicon alloy is used in automotive engines for cylinder castings, AA 390 (UNS A03900) with 17% Silicon for high wear resistance. Common aluminum alloys for die casting are summarized as follows:

Zinc can be made to close tolerances and with thinner walls than Aluminum die casting, due to its high melt fluidity. Zinc is alloyed with Aluminum (4%), which adds strength and hardness. The casting is done at a fairly low temperature of 425 ºC (800 ºF) so the part does not have to cool much before it can be ejected from the die. This, in combination with the fact that Zinc can be run using a hot chamber process allows for a fast fill, fast cooling (and ejection) and a short cycle time. Zinc alloys are used in making precision parts such as sprockets, gears, and connector housings.

Copper alloys are used in plumbing, electrical and marine applications where corrosion and wear resistance is important.

Minimum wall thicknesses and minimum draft angles for die casting are :

Die-castings are typically limited from 20 kg (55 lb) max. for Magnesium, to 35 kg (77 lb) max. for Zinc. Large castings tend to have greater porosity problems, due to entrapped air, and the melt solidifying before it gets to the furthest extremities of the die-cast cavity. The porosity problem can be somewhat overcome by vacuum die casting

From a design point of view, it is best to design parts with uniform wall thicknesses and cores of simple shapes. Heavy sections cause cooling problems, trapped gases causing porosity. All corners should be radiused generously to avoid stress concentration. Draft allowance should be provided to all for releasing the parts-these are typically 0.25º to 0.75º per side depending on the material.

The component can be produced in either Aluminium or Zinc. Using a permanent mould called Gravity Die Tooling. Gravity Die-Castings are produced by molten metal entering an aperture in the Gravity Die Tooling, this aperture allows metal to enter the cavity to form the cast shape of the Gravity Die-Casting required by the customer.

Gravity Die-Casting produced in all grades of Aluminium and Zinc. Higher volumes of precision castings are achievable using the Gravity - Die Casting, external or internal is either produced by means of a purpose made steel core or as previously mentioned an Airset sand core.

Gravity Die-Castings produced are cost effective for quantities of a semi to high volumes. The finishing operations on a Gravity Die

Casting are minimal compared to a conventional sand casting, usually on a Gravity Die Casting the joint line is minimal and in some circumstances the need for an operation is not required.

Mechanical means are some times required for opening and closing of Die Tooling if the Gravity Die-Casting to be produced is large and complex.

Gravity Die-Castings if required by specification can be heat treated to adjust or improve its characteristics

Improvement to production rates of Gravity Die-Casting can be improved by the use of multiple tooling.

A Gravity Die-Tooling is able to produce Gravity Die-Castings for several years without the need of refurbishment.

Casting often use a variety of metal materials, coke, wood, plastic, gas and liquid fuels, such as modeling materials. Have the necessary equipment used in various metal smelting furnace, a Mixer with the various Mixer, a shape-made batteries used in various molding machine, machine-made batteries, cleaning up the castings used for loading sand, Shot Blasting Machine And so on. Casting is also available for special machinery and equipment, and many transportation and material handling equipment.

Casting and other technology have different characteristics, mainly wide adaptability, needed materials and equipment, pollution of the environment. Casting will have dust and harmful gases and noise pollution to the environment, compared to other machinery manufacturing processes to become more serious, need to take measures to control.

aluminum die Casting product development requirements of the trend is casting a better overall performance, higher accuracy and less headroom and clean the surface. In addition, the requirements of energy-saving society and restore the natural environment of the call also getting higher and higher. To meet these requirements, the new cast alloy will be developed, the new smelting technology and new equipment will be corresponding.

die Casting the mechanized production continuously improve the degree of automation in the same time, to be more flexible production development, to expand the volume and variety of different production adaptability. Conserve energy and raw materials of new technologies will be giving priority to the development, have little or no pollution of the new equipment, new technology will be the first attention. Quality control technology in all stages of testing and nondestructive testing, stress determination, there will be new development.

Die casting is a method of casting. Forging is a die-casting process in a dedicated die-casting machine on the completion of the forging process. The basic process is: first liquid metal casting low-speed or high-speed filling into the cavity of the mold, a mold cavity of the activities, which along with liquid metal cooling process of forging pressure, not only to eliminate the shrinkage of rough Shrinkage Defects, but also to achieve the internal organization of rough forging state of broken grains. The mechanical properties of rough significantly improved. In addition, the technology produced by the rough, the surface finish to seven (Ra1.6), such as cold extrusion process or machining from the surface, a metallic luster. Therefore, we will be casting forging process known as the “ultimate forming process,” than the “no cutting and less cushion forming process” has taken one step further. There is also a die-casting forging advantage of features, in addition to the traditional casting production materials, it also can be used deformation alloy, forging alloy to produce a very complicated structure of the parts. These alloys brands include: hard aluminum super-hard aluminum alloy, aluminum forging, such as LY11, LY12, 6061,6063, LYC, LD, etc.). These materials tensile strength than ordinary casting alloys nearly doubled, aluminum car wheels, trailers, and so hope to use a higher intensity of impact resistant material production of components, have a more positive significance.

I. Introduction pressure die casting foundry as die-casting, is a liquid alloy will melt into the indoor pressure, high-speed steel mold cavity filling, and alloy liquid under pressure and the solidification of a casting method of casting. Die-casting method different from the other casting is the main characteristics of high-voltage and high-speed. ① liquid metal is under pressure filling the cavity, and at a higher pressure crystallization of solidification, the pressure for the common 15-100 MPa. ② liquid metal at high speed filling cavity, usually in the 10-50 m / s, and some can be more than 80 meters / second (cavity through the gate into the line speed - speed in the gate), the liquid metal Filling the very short time, about 0.01-0.2 seconds (depending on the size of different casting) to fill the cavity. Die-casting machine, die-casting alloy die-casting and casting molds are the three elements of production, one can not do. The so-called die-casting process is organic these three elements to be integrated use of so that it can have steady rhythm and efficiently produce the appearance of good internal quality, size or design of the agreement in line with the requirements of qualified castings, and even high-quality castings. 1, die-casting machines (1) the classification of die casting machine die casting machine press room heated conditions can be divided into the room and pressing cold press room two categories. And the press room and placed the location of different molds, cold chamber die-casting machines can be divided into vertical, horizontal and vertical all three forms of die casting machine.

Die casting alloys are normally non-ferrous, and there is a large number available with a wide range of physical and mechanical properties covering almost every conceivable application a designer might require.

Aluminum and zinc alloys are the most widely used, and are followed by magnesium, zinc-aluminum (AZ) alloys, copper, tin and lead.

Zinc, lead and tin based alloys are classified as low melting point metals, all melting at less than 725oF (385oC). Zinc-aluminum (ZA) alloys have a slightly higher melting range of 800oF to 900oF (426oC to 482oC). Aluminum and magnesium alloys are considered to be moderate melting point alloys, being cast in the 1150oF to 1300oF (621oC to 704oC) range. Copper alloys are considered to be high melting pint, over 1650oF (899oC). Low melting point alloys are cast in hot chamber machines. Intermediate and high melting point alloys are cast in cold chamber machines. In recent years, specially designed hot chamber machines for die casting magnesium alloys have come into use.

There are many kinds of die casting, by modeling on the customary method is divided into: ① ordinary sand casting, including the wet sand and dry sand and chemical hardening Sand three categories. ② special casting, according to modeling materials can be divided into natural mineral sand as the main form of special casting (such as investment casting, mud-casting, casting workshop shell casting, vacuum casting, is type casting, ceramic-casting , Etc.) and metal casting as the main material of special casting (such as metal-casting, pressure casting, continuous casting, low pressure casting, centrifugal casting, etc.) two categories. Casting process usually includes: ① mold (so that solid become liquid metal casting containers) prepared by casting materials used can be divided into sand, metal, ceramic, clay, graphite type, the frequency of use can be divided into one-time Type, semi-permanent and permanent-type, ready to mold the pros and cons that affect the quality of casting a major factor; ②aluminum die castingmetal melting and casting, casting metal (cast alloy) are the main cast iron, cast steel and nonferrous metal alloy casting; ③ casting processing And testing, treatment including the removal of casting and casting surface core foreign body, with pouring riser, and relief grinding burr, such as projections of Phi slit and heat treatment, plastic surgery, such as anti-rust treatment and rough.

iron casting, process can be divided into three basic components, namely preparations for metal casting, casting and casting prepared to deal with. Metal Casting is casting for the production of metal castings casting material, it is a metallic element as the main ingredients, and add other metals or non-metallic elements and composition of the alloy, called on the habits of casting alloys, the main cast iron , Cast steel and nonferrous metal alloy casting.

The main die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin. Specific dies casting alloys include: ZAMAK, zinc aluminum, AA 380, AA 384, AA 386, AA 390, and AZ91D magnesium. The following is a summary of the advantages of each alloy:

Zinc: the easiest alloy to cast; high ductility; high impact strength; easily plated; economical for small parts; promotes long die life.
Aluminum: 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 alloy 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.
Lead and Tin: high density; extremely close dimensional accuracy; used for special forms of corrosion resistance.
Maximum weight limits for aluminium, brass, magnesium, and zinc castings are approximately 70 pounds (32 kg), 10 lb (5 kg), 44 lb (20 kg), and 75 lb (34 kg), respectively.

The material used defines the minimum section thickness and minimum draft required for a casting as outlined in the table below.

he primary function of prototype die casting is to validate both the design and the production process for casting and secondary machining which will be used, ultimately, to produce castings in volume. Low pressure or gravity feed die casting using sand, plaster or graphite cavities are effective methods of validating the product design, however, it does not provide any information regarding the production process or the true properties of an aluminum or zinc high pressure die casting. Prototype programs usually require a substantial number of engineering changes which can easily be incorporated into a P20 steel tool from CAD data.

Most companies, especially those producing automotive or electronic products incorporating die castings, should be validating both the product design and the required production process