What Is Die Cast Molding?

The die casting method is used to manufacture things like toy cars.

Used in a variety of industrial, commercial and consumer products, die cast parts can be found in many common items like cars and toys. Created by placing molten metal into pressurized steel molds the die cast pieces can be very complex, and because of the reliability of the technology, identical parts can be manufactured with great accuracy.

Die Cast History

The mid-1800's saw the development and use of pressure-injected die casting, but the technology was limited for the first 20 years to the production of printer's type and the use of tin and lead. By the end of the 1800's other shapes and parts, like phonographs, began to be produced using alloys like zinc, aluminum and magnesium. These, as well as magnesium and copper, remain popular die casting metals today.

Types of Die Cast Methods

There are two predominant methods of commercial die casting. The hot chamber and cold chamber methods both utilize injection systems, but in different ways. The hot system is used for metals with low melting points such zinc, copper and lead. The injection system itself is immersed in a bath of molten metal where it then fills with the liquefied metal. The cold chamber method is used for metals with higher melting points like aluminum. A manual or automatic ladle pours the molten metal into a cylindrical sleeve and is then sealed under pressure to cool.

Die Cast Advantages

The die casting technique is more useful than other production methods because it creates durable, identical materials and parts in more shapes and types than what is capable by other manufacturing processes. The accuracy of the die casting process, as well as the strength and easy assembly of its finished products, makes it an efficient commercial manufacturing method that is valuable in a wide range of industries.

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How to Generate Runner Sizes for Plastic Injection Mold Design

The runner feeds the molten plastic from an injection machine into the mold to form the desired plastic part. The length of the runner is completely dependent on the part design, so there are no specific rules regarding overall length. It is the diameter of the runner that impacts part quality and cost and therefore it should be sized with some care. Once the runner freezes, no more plastic can be injected into the part. The runner should be sized to make sure that part receives sufficient plastic without excessive fractional heating, while freezing quickly enough to minimize cycle time.

Instructions

1.                            Calculating Runner Diameter

1

Determine thickest cross-section of the desired part.

2

Where part design allows, locate runner nearest to the thickest cross section of the part. If the part is of a uniform thickness, locate the runner near the center or along the longest edge, as part design allows.

3

Runner diameter should be between 75% to 100% of the part thickness where the runner is located.

4

Based on your injection machine type, determine the acceptable pressure drop for an injection cycle.

2.                            Calculate Injection Pressure Drop

5

Calculate runner volume. V = pi x r^2 x L, where pi = 3.14159, r = runner radius and L = runner length.

6

Calculate volumetric flow rate (Q) based upon your pre-determined fill time. The fill time is a function of material type, part thickness, and desired cycle time. The molder must know this independent of this exercise. Q = V/t, where t = seconds of fill time.

7

Calculate shear rate (S). S = 4Q/(pi x r^3)

8

Calculate the pressure drop (P). P = (S x m x 2L)/r, where m = melt viscosity of the plastic. The melt viscosity is a function of S, melt temperature, and the material. The molder must know this independent of this exercise, although many plastic suppliers can help with this.

9

Compare pressure drop to predetermined acceptable pressure drop. If improvement is desired, change the runner diameter and repeat the exercise. Repeat calculation until an acceptable runner diameter is found.

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What’s hot runner mold?

  It use an assembly of heated components in plastic injection molds that inject plastic into the cavities of the mold. There are two general types of runnerless molds  - the insulated system and the hot runner system. Hot runners mold retain the advantages of the insulated 
  runner system over conventional cold runner system and eliminate a number of the disadvantages. Hot runner system is one of the more important enhancements you can incorporate into a mold to improve molded part quality, reduce production times and remain price competitive

  Injection Mold with Hot runner Solution will use reliable hot runner system and mold design tools. Our engineering department work harder and quicker than any other supplier to offer you new design ideas and mold concepts using any kind of hot runner system.with long history of experience and reliability for plastic injection molding and hot runner mold manufacturing,  we can deliver the best solutions. 
  Although there are many hot runner manufactures , a few major components is same:
  1. Hot runner plate (MANIFOLD)
  2. Nozzle

3. Temperature Controller
  4. Auxiliary parts

  Advantage of hot-runner mold in injection molding industry  

 Why some many customer select hot runner to make injection mold .This is mainly due to such injection mold has following salient feature:

  Less plastic raw materials: in the age of expensive oil and raw materials . hot runner technology is the effective way to reduce the materials cost.

  Quickly cycle time for injection molding, Due to no cooling time constrains runner system.

  Plastic can be more uniform state injection into each cavity, the result is consistent quality
  parts. Such injection molding components of good quality and low residual stress after ejection part distortion. reduce product costs, improve product quality

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