| Design manual of the mold (A guide to mold design) |
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| Flow analysis |
There is a flow analysis as a method of grasping filling sequences before casting.
Flow analysis is a useful method to study the filling behavior of molten metal in a die cavity.
By using athe flow analysis, it is possible to predict the appropriate position of gates and overflows.
Referring to the information acquired from the analysis, the risk and time of mold making can be minimized and one can proceed to mass production rapidly.
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| Example of a flow analysis |
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| A casing for notebook type personal computer |
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| Selection of injection machine |
| The size of injection machine is determined by calculating the required clamping force from the projected area of the product you are going to mold. Suppose that the total projection area (including sprue , runner and overflow) is A cm2 and the peak metal pressure in the die cavity is P kg/cm2 at the time of injection , the required clamping force is calculated as follows. |
| Clamping force => A x P x safety factor |
| In the thixomolding , the die peak metal pressure in die cavity is about 800kgf/cm2. Since the pressure is bigger than that for plastics (250~500kgf/cm2) , a bigger injection machine with a bigger clamping force is needed. |
| The safety factor depends on the thickness of a the product is , the injection pressure increase, and quicker the injection speed up. The safety factor of 1.2~1.3 is usually used. When the exact projected area, including sprue , runner and overflows, is not known , the total projection area which is calculated by 1.3 times that of product would be a good estimation. It is necessary to check after completing a the design. |
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| Mold design |
| The basic structure of the mold for thixomolding is quite similar to that of the plastic mold. But the details such as gates , overflows , etc. and material are close to those of die casting. The most important step in the mold design is to determine the proper arrangement of cavity in order to get a sound product without defects. It that is achieved by setting a proper position and shape of gates, which molten metal is pored from, allowing a reasonable metal flow in the cavity , and maintaining enough path which gas in the cavity get away through. |
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Product design review |
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Determination of method and position of secondary working which might be necessary after molding |
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Positioning of cavity |
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Selection of parting line |
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Position and length of gates and runner |
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Area, forms and number of gates |
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Position and volume of overflows |
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Selection of gas vent position |
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Determination of detail design |
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