There are two main functions of the exhaust tank: firstly, the air in the cavity is excluded from the injection of molten material. The second is to exclude the various gases produced during the heating process. The more thin wall products, the farther away from the gate, the opening of the exhaust groove is particularly important. In addition, for small pieces or precision parts, but also should attach great importance to the opening of the exhaust slot, because in addition to it can avoid products surface burns and injection quantity is insufficient, also can eliminate the various defects of the products, reduce the pollution of the mould, etc.

    So how does the exhaust of the cavity be sufficient? Generally speaking, if the injection rate is injected at the highest injection rate, it can be considered that the exhaust in the cavity is sufficient.

Exhaust way

    "There are many methods of cavity exhaust, but every method must be guaranteed: the exhaust groove is in the exhaust, and its dimensions should be designed to prevent the material from spilling into the slot; The second is to prevent clogging. Therefore, from the surface of the cavity to the cavity of the cavity in the direction of the cavity, the length of the exhaust groove above the length of 6-12mm shall be about 0.25 to 0.4mm. In addition, the number of exhaust slots is harmful. Because it is very dangerous to cause cold flow or split of the cavity material if the pressure of the locking mode of the exhaust slot in the cavity is very high. "In addition to outside the parting surface of cavity exhaust, also can be in the end of the pouring system of material flow set exhaust slot location, and leave gaps around the ejector rod achieve the purpose of exhaust, because of the depth, width and exhaust slot location choice, if not appropriate, the flash burr, will affect beautiful and precision of the products. Therefore, the size of the above clearance is limited to prevent the flying side of the ejector rod. "It should be noted here that, in the exhaust of a piece of gear such as gears, it may not be possible to have even the smallest of the flying edges. This type of assembly is best to exhaust in the following manner:. (1) thoroughly scavenging the gas in the channel;

      (2) spray pellet treatment with the surface of the parting surface with the silicon carbide abrasive of 200 #. In addition, the exhaust groove at the end of the pouring system is mainly used to refer to the exhaust groove at the end of the diverter channel. Its width should be equal to the width of the shunt channel and the height is different from the material.

     molds

     Design method

     "According to the experience of years of injection mould design and product testing, this paper briefly introduces the design of several exhaust slots. For the product mold of complex geometry, the opening of the exhaust groove is best determined after several trial modules. And the overall structure of mould structure design, its biggest disadvantage is the exhaust. For the overall mode core, there are several exhaust methods:. (1) using the slot or installation part of the cavity; (2) using the inlaid seams on the side;

   (3) local helical shape;

    (4) in the longitudinal position, top of the belt with grooves and open process holes;

    (5) when the exhaust is extremely difficult, the parquet structure is adopted; If some mould corner is not easy to open vent groove, should first under the condition of product appearance and its accuracy is not affected, the appropriate spell mould to set processing, in this way, not only is advantageous to the processing and exhaust slot, sometimes also can improve the existing processing difficulty and easy maintenance.

    molds

    Design dimensions of vent tank

    Design of exhaust groove during thermosetting plastic forming

    "The exhaust of thermosetting material is more important than thermoplastic material. First, the diversion channel in front of the gate should exhaust. The width of the exhaust groove should be equal to the width of the shunt channel and the height is 0.12mm. The cavity of the cavity should be exhaust, each vent should be separated by 25mm, width of 6.5 mm, height of 0.075-0.16mm, depending on the material's fluidity. Softer materials should be of lower value. The ejector rod should be enlarged as far as possible, and in most cases, three or four high 0.05mm planes should be ground out of the top of the rod, and the direction of the grinding should be in the direction of the length of the rod. Grinding wheel with fine grain size. The top of the rod end should be worn out 0.12mm chamfer, so that if the edge is formed, it will stick to the piece.

    conclusion

    "Open the exhaust slot appropriately, can greatly reduce the injection pressure, injection time, holding time and clamping pressure, molding plastic from difficult to easy, thus improve the production efficiency, reduce production cost, reduce the energy consumption of the machine..

It's not all necessary to vent through the vent, and the other ways of venting

In the mould, a reasonable exhaust structure should be provided to avoid the defective products caused by the exhaust. The common gas modes are as follows:

    1. Exhaust vent

For the moulds of large and medium sized plastic parts, there are many gases to be excluded. Usually, the exhaust groove should be opened on the concave side of the parting surface. The position of the exhaust groove is in the absence of the melt flow, and the exhaust groove size is the principle of the gas can be discharged without overflow. The width of the exhaust groove is generally 3-5mm, the depth is less than 0.05 mm, the length is 0.7-1.0mm, and the depth of the commonly used vent tank can be verified by the plastic mould technical manual >.

    2. Exhaust of the parting surface

For small molds, it can be used to exhaust the gap between the parting surface, but the parting surface should be located at the end of the melt flow.

    3. Slot and slot exhaust

For a combination of a concave or a cavity, it can be used to exhaust the slit.

    4. Clearance of putter

Use the putter to fit in the gap between the template or the type core, or deliberately add the putter to the template. 

    5. The powder does not burn with gold The powder unsintered alloy is sintered with spherical particle alloy, which is poor in strength, but loose in texture, allowing gas to pass through. It is necessary to place a piece of such alloy in the area where the exhaust is needed, but the bottom vent hole should not be too large to prevent the cavity pressure from extrusion.

   6. Exhaust shaft exhaust

On the outside of the plastic melt confluence, a hole is set up to allow the gas to be discharged into the air, and good exhaust effect can be obtained.

   7. Mandatory exhaust

In the area of the enclosed gas, the exhaust rod is set. This method has good exhaust effect but leaves the marks on the plastic parts. Therefore, the exhaust rod should be located in the hiding place of the plastic parts.