What is the role of mold venting?
There are two main functions of the mold venting slot: First, to remove the air from the mold cavity when injecting molten material; Second, to remove all kinds of gases generated by the material during the heating process.
The more thin-walled products, the farther away from the gate, and the more important the opening of the venting exhaust slot. In addition, for small or precision parts, also pay attention to the opening of the mold venting exhaust slot because it can prevent the product surface burns and injection volume is not enough, but also can eliminate various defects of the product, reduce mold pollution, etc.
There are many ways to exhaust the mold cavity, but each method must ensure that: the mold venting exhaust slot is in the exhaust simultaneously. The design size should be able to prevent material overflow into the mold venting slot and; secondly, to prevent blockage.
The opening position of the exhaust port should not face the operator to prevent the molten material from accidentally ejecting and injuring people. In addition, it can also use the ejector rod and the ejector hole with the gap, the top block and off the template, and the core with the gap to exhaust mold air.
The role of the mold venting exhaust slot
The role of the venting exhaust tank has two main points
Excluding the air in the mold cavity when injecting molten materials
Exclude the material in the healing process of various gases
The more thin-walled products, the move away from the part of the gate, the opening of the exhaust slot is particularly important.
In addition, for small parts or precision parts, it is also important to pay attention to the opening of the venting exhaust slot, because it can avoid surface burns and insufficient injection volume of products, but also eliminate various defects of products, reduce mold pollution, etc.
How is the venting of the mold cavity considered adequate? Generally speaking, if the melt is injected at the highest injection rate and no scorch is left on the product, the exhaust of the mold cavity can be considered adequate.
Mold venting solutions
There are many ways to vent the mold cavity, but each mold venting solution must ensure that the mold vent exhaust tank should be designed to prevent the material from overflowing into the tank while exhausting; secondly, it should prevent blockage.
Therefore, measured from the inner surface of the mold cavity to the outer edge of the mold cavity body, the length of 6-12mm above the mold vent exhaust slot part, the slot height should be put about 0.25-0.4mm.
In addition, it is harmful to have too many mold venting exhaust slots. Because if the clamping pressure acting on the parting surface of the mold cavity without the venting groove is very large, it is easy to cause cold flow or cracking of the mold cavity material, which is very dangerous.
In addition to mold venting the cavity on the parting surface, mold venting can also be achieved by setting up mold venting slots at the end of the material flow in the casting system and by leaving a gap around the ejector rod, because the depth, width, and location of the venting slots are chosen.
If the depth, width, and location of the mold venting groove are not appropriate, the resulting flying burr will affect the beauty and accuracy of the product. Therefore, the size of the above clearance is limited to prevent the emergence of flying edges around the ejector rod.
Special attention should be paid here to the fact that even the smallest flutter may be undesirable when mold venting a part such as a gear, which is best vented by
Complete removal of gas from the runner.
Shot blasting of the mating surface of the parting surface with a silicon carbide abrasive with a particle size of 200#.
In addition, the mold venting groove at the end of the pouring system flow, mainly at the end of the manifold, should be equal in width to the width of the manifold and vary in height depending on the material.
Mold venting design
For the complex geometry of the product mold, the opening of the mold vent exhaust slot is best to be determined after several mold trials. The biggest disadvantage of the overall structure of the mold structure design is that the mold venting is not good.
There are several mold venting solutions for the overall cavity core.
Use the mold venting slot or insert the mounting part of the cavity.
Using the side insert joints
Partially made into a spiral shape
Installing a slatted core with slots in the longitudinal position, opening process holes
When the mold venting is extremely difficult, the use of inlay structure, etc.; If some of the dead ends of the mold are not easy to open the mold venting exhaust slot, the first should not affect the appearance and accuracy of the product, the mold should be properly changed to inlay processing so that not only conducive to the processing of mold venting exhaust slot, and sometimes can improve the initial processing difficulties and ease of maintenance.
Properly opening the mold venting exhaust slot can greatly reduce the injection pressure, injection time, holding time, and clamping pressure, so that the molding of plastic parts from difficult to easy, to improve production efficiency, reduce production costs and reduce energy consumption of the machine.
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