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Types and selection for die-casting machine

Types and selection for die-casting machine

 1.1 Types of die-casting machine
the die-casting machines are generally divided into the hot chamber die casting machine and cold chamber die casting machine class. Cold pressing chamber die casting machine according to the structure and layout of the pressure chamber is divided into horizontal die casting machines, vertical die casting machine (including the two kinds of vertical die casting machine).

Hot pressing chamber die casting machine (referred to as hot air die casting machine) pressure chamber is immersed in the liquid metal insulation melting crucible injection components are not directly connected with the base, but mounted on the top of the crucible. The advantages of such a die casting machine is a simple production processes, high efficiency,; Metal consume less, the process is stable. Pressure chamber, injection punch immersed in the liquid metal for a long time, affecting life. And more likely to increase the iron content of the alloy. Hot pressing chamber die casting machine is used mostly for die-casting zinc alloy and other low melting point alloy castings, but for die-casting light aluminum, magnesium alloy die castings.

The pressure chamber and the holding furnace of the cold chamber die casting machines are separated. Die-casting removed from the holding furnace, the liquid metal poured into the pressure chamber die-casting in Figure 1 is a vertical die casting machine die casting process schematic.

Die-casting process schematic of a horizontal die casting machine - injection punch - pressure chamber 3 - liquid metal - setting 5 - acting - cavity - runner cavity 8 - more than expected

   1.2 the choose of die-casting machine
Not all the actual production of each die casting machine can meet the needs of die-casting products, but must be selected depending on the circumstances, generally from the following two aspects to consider:

1) selected according to different varieties and quantities of
In organizations of many varieties, small batch production, the general choice of the hydraulic system is simple, adaptable, able to quickly adjust the die casting machine, in the mass production of the few varieties to choose high with mechanization and automation and control institutions efficiency of die casting machine; on a single species of mass production of castings can be used die casting machine.

2) casting structure and process parameters to select
Size of casting shape, weight, wall thickness and other parameters on the selection of die-casting machine. Casting weight (including the gating system and the overflow tank) should not exceed the rated capacity of Die Casting Machine, but can also be too small, so as to avoid the waste of the die casting machine function string. Generally the rated capacity of the die-casting machine to check the instructions. The die casting machine has some of the largest and the smallest distance, pressure casting and thickness height to have a certain limit, if the die-casting thickness or castings height is too large it may take no casting.

    2 die casting process
In the die casting production, die casting machine, die-casting alloy and die-casting type are the three elements. Sucked the three elements of the die casting process for the right combination and the use of the process. Various process parameters to meet the needs of die-casting production.

    2.1 choice of pressure and velocity
The injection pressure of choice should be determined according to the different alloys and castings structural characteristics, Table 1 shows the empirical data.

Table 1 of commonly used casting alloy pressure (kPa)

 Casting wall thickness <3mm
 Casting wall thickness> 3mm
Simple structure
 Complex structure
 Simple structure
 Complex structure
Zinc Alloy
Aluminum alloy
Aluminum-magnesium alloy
Magnesium alloy
Copper alloy
Choice of filling speed, the general requirements for thick-walled or internal quality higher casting, should choose a lower filling speed and high boost pressure high casting and casting; for thin wall or surface quality requirements should be selected higher than the calendar and high filling speed.

    2.2 pouring temperature
The pouring temperature from the average temperature of the liquid metal into the cavity pressure set pressure indoor liquid metal temperature measurement is not convenient, usually holding furnace temperature. The pouring temperature is too high, shrink, make casting easy to crack, crystal capsules, can cause stick-type; pouring source is too low, easy to produce cold shuts, surface pattern and pouring lack of defects. Therefore, the pouring temperature and pressure, taking into account the die-casting temperature and the filling speed.
Die-casting machine it
 2nd Floor
 2.3 die-casting temperature
The type of casting pressure before use to warm-up to a certain temperature, and more generally to gas, torch, electrical or induction heating. In continuous production, die casting temperature is often increased, especially in die casting high melting point alloy to rise quickly. Temperature is too high, in addition to the liquid metal stick External slow, casting cooling, so that the coarse grains. Therefore, the die-casting-type high temperature of the cooling measures should be adopted. Usually cooled with compressed air, water or chemical media.

    2.4 Filling, holding pressure and open type
1) The filling time
From the liquid metal into the cavity to stop the play is full of cavities, the time required is called the filling time. Filling the length of time depends on the size and complexity of the casting volume. And simple castings, filling time is relatively long, complex and thin-walled castings filling time is short. Closely related to the need to correctly determine the filling time and within the size of the cross-sectional area of ​​the gate or inside the gate width and thickness.

2) with the pressure, and type time
From the liquid metal filled cavity within the gate completely solidified, and continue in the punch under the action of the injection duration, called the holding pressure time. Holding pressure time, depending on the material and wall thickness of the casting.

Should be open type with the pressure, remove the castings. Die casting open from the end of the injection, known as the open type, open type should be controlled accurately. Open type time is too short, due to alloy strength is still low, may be casting top and deformation caused by the fall of the die-casting type; open type too long, the casting temperature is too low, shrink large, core pulling and top out casting The resistance also. Generally open casting wall thickness of 1 mm required 3 seconds to calculate the adjustment and then through a trial.

    2.5 die-casting with coating
Die-casting process, in order to avoid casting and die casting welding, casting the top of the frictional resistance reduction and to avoid the excessive heat of die-casting type and the use of coatings. Paint requirements:

    1) at high temperatures, has good lubricity;

    2) low volatile point at 100 ~ 150 ℃, the diluent can quickly volatile;

    3) Die Casting and Die-corrosive effect;

    4) stable performance in air diluent should not be volatile over decisions without thickening;

    5) at high temperatures without precipitation of harmful gases;

    6) does not die casting cavity surface fouling.

Table 2 are commonly used in die casting coating

Table 2 die-casting with coating and method of preparation

Serial number
 Raw material name
 Ratio (%)
 Method of preparation
 Scope of application
Colloidal graphite
 Into oil
 1. Used for the aluminum alloy on the anti-sticking effect
2 injection punch, and easy to bite part of the pressure chamber
 Natural beeswax
 Block or maintained at a temperature not higher than 85 ° C molten state
 Molding surface of the requirements for zinc alloy smooth part
 Oxidation of sodium and water
 The water is heated to 70-80 oC plus sodium oxide, Stir
 For easy to produce a stick-type parts of alloy erosion
 Graphite oil
 Stone grinding sieved (200 o) by adding the power of about 40 ℃ oil Stir
 For aluminum alloy 2. Injection punch, part of the effect of pressure chamber
 Spindle oil
 30o 50o
 For zinc alloys for lubrication
  2.6 fettling
Clean-up of the casting is a very heavy workload, the workload is often 10 to 15 times that of the die-casting workload. Therefore, with the improvement of the productivity of die casting machine, the increase in production, casting cleaning work mechanization and automation is very important.
1) removal of the gate and flash
Removal of the gate and the equipment used in the flash punch, hydraulic machines and friction press, under mass production, according to the casting structure and shape of the mold, punching time to complete the clean-up task.

2) The surface cleaning and polishing
Surface cleaning and more ordinary polygonal drum and shake buried cleaning device. Small quantities of small pieces that can be used polygonal clean the rollers on the surface requires high decorations can be used to buff polishing cloth or leather. Cleaning machine for mass production of castings can be used shells vibration.
Clean up after casting in accordance with the requirements, and also for surface treatment and impregnation, in order to increase the luster and prevent corrosion, improve the air tightness

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