Basic structure of mold
Quality
Core side
Cavity side
The mold could be roughly divided into the following systems：
- 1.Forming system：
After core and cavity are closed, a space will be formed in the tooling. According to the difference of product design, the features could be designed in cavity or core 100% or be designed in cavity and core in a special ratio. the engineer needs to consider draft angle, the ruin of molten metal, the location of parting line and difficulty of inspection. - 2.Mold base：
This system contains tooling plates and base structure units, the function of these parts is assembled and fix mold, and make sure this mold could be put on die casting machine correctly. - 3.Guild system：
Guild parts will make mold to close and separate correctly and make mold could match the requirement from customers. - 4.Ejector mechanism system：
The function of this system is pushing the product out of the mold. This system contains ejector pin and reset parts. About the push rod at the important and vulnerable part (sprue gate), it should be made form the same material as the product. - 5.Gating system：
This system refers to the channel connecting the cavity and the sprue gate.
This channel will guild molten metal into cavity in the correct direction and the design of channel will determine the speed and pressure of the molten metal during the forming stage. - 6.Overflow system：
It contains exhaust groove and overflow groove system. The function is removing the gas in the channel and cavity.
The overflow is usually placed at the end of molten metal channel. This system also could maintain the mold temperature. - 7.Core pulling system：
This system usually is used when the core extraction direction and the parting line direction are different (such as the side hole of the product).
It could help products to be pulled out from the mold easily. - 8.Cooling – heating device：
This system could make the temperature match the process requirements, and this device also could make tooling life being extended. - 9.Other extra parts：
It generally refers to bolts and positioning parts that connect and fix each structural unit parts , or some parts which are suitable for special products.
The mold design is provided by the customer with drawings, and the mold department of Fuchia Industry develops the mold based on the drawings. The following factors need to be considered when designing the die casting mold
Reducing the weight of product
When we design the die casting product, we must reduce the volume and weight as possibly. Less weight could make less cost. If die casting product is heavy, the production process will need more time.
use “Rib” to increase the strength of product
Rib could be used to increase the strength of die casting product, especially for the thin wall. Considering the ejection pin’s location and the flow of molten metal, designer must choose suitable location to put ribs.
Cooling shrinkage of die casting product
All alloy will have cooling shrinkage phenomenon during the die casting process Cooling shrinkage could not only make product separating from mold, but also have possibly to demolding failed. The draft angle could be used to solve this issue during the design process.
Application of draft in die casting process
The draft usually is used to make product separating from the mold more easily. Surfaces with draft angles are usually smooth.
Consistency of die casting profiles
The more consistent of the cross-sectional area of die casting product, the more conducive to the flow of molten metal. The drastic change of the cross-sectional area will cause fluctuations and product will have the issue of porosity.
The fillet and corner of die casting products
The design of die casting product should avoid sharp edge and drastic change in cross-sectional area. The fillet should be used in corner because it could increase the strength and avoid the issue of filling not completely.
Smoothness of die casting products
The smoothness of die casting products depends on the surface of tooling. The tooling surface is smoother, the smoothness of die casting is better.
Parting line and ejector pin location
The parting line is the joint of cave and cavity side, and it should be as straight and flat as possible. The ejector pin is used to pull the product out of the mold, designers usually try to minimize the ejector pin marks.
The identify mark of product
The identify mark is used to show the company’s logo, product’s code, and cavity number. It could help people to inspect products more correctly and faster.
Slide of product
Slide usually is used to form some difficult features or form some features which directions are different with parting line. However, using slide will increase the cost of tooling. Designer usually try to avoid to use it unless necessary.
Die casting function merge
Designers could combine multiple functional parts on one die casting part to reduce the cost of handling, storage, and assembly.
multi-cavity mold
Multi-cavity mold may reduce the price of products, but the following conditions are required: @Additional cavity should not make mold to use larger die casting machine to produce products, because the larger die casting machine needs more energy to work. It is meaning the cost of startup will be increased. @Additional cavity could not decrease the yield rate of production.
If the product has several similar parts , the customer could consider using the same mold and using different secondary operation to processing them. It could reduce the cost of molds.
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Hot chamber die casting process
- The mold is closed and the piston is raised, then the molten metal will be pulled into the cylinder.
- The injection port will be closed, the plunger will pull the molten metal in the cavity. Then the molten metal will be solidified during this process.
- The mold is opened, product will remain on one side of mold
- The ejector pin will push the products, then mold is closed and the first process will start again.
Cold chamber die casting process
- The mold is closed and the molten metal will enter in the molten metal storage.
- The plunger will pull the molten metal into the cavity and the molten metal will transform the metal state to solid state.
- The mold will be opened and the product will be the side of ejection.
- The ejector pin will pull the product out of the cavity , then the die casting process will return to the first step.
After the mold design is completed, it is necessary to test whether the product produced by the mold match the requirement. It will undergo various strict test. Including the structure inspection, the inspection of material (SGS), dimensions inspection and environment resistance test.
Construction test
After the T1-1 sample was prepared, the staff will start to confirm whether the product match the required by the customer, whether there are blister or stain on the surface. If there are any defects were found, the mold will be modified immediately.
Material inspection
After the sample was prepared , it will be send to the quality assurance department. The metallographic grain will be observed with a microscope. When the molten metal was pulled in the cavity and cooled , two problems will be happened possibly , one is the changes of grainsize will affect the strength of the product. Another is the invisible defects will exist during the cooling process (ex. Porosity). If these two issues existed , the temperature gradient of cooling process is needs to be modified.
dimensions inspection
The dimensions inspection is very important in the mold test . because the die casting products usually are used to components of precision instruments ,the dimensions requirements will be accurate to third to fourth decimal places. Because the deviation is out of spec, it will cause the assembly to failed. Therefore, we will make all dimensions match the specification.