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[Plastic extrusion supplier]Casting system of plastic extrusion molding

May. 24, 2019

Injection mold casting system shared by plastic extrusion supplier.

The gating system refers to the part of the runner before the plastic enters the mold cavity from the nozzle, including the main flow path, the cold material hole, the shunt path and the gate, etc.

The pouring system, also known as the runner system, is a group of feeding channels that lead the plastic melt from the nozzle of the injection machine to the mold cavity. It is directly related to the molding quality and production efficiency of plastic products.

The main flow path

It is a section of the channel connecting the injection molding machine nozzle to the diverter or cavity in the mold. The top of the main flow channel is concave to connect with the nozzle. The diameter of the inlet of the main flow channel should be slightly larger than the diameter of the nozzle (0.8mm) to avoid the overflow, and to prevent the interception caused by inaccurate connection between the two. The inlet diameter is determined according to the size of the product, generally 4-8mm. Mainstream way to expand inside diameter are 3 ° to 5 ° Angle, so that the flow channel in January release.

The cold material hole

It is a hole located at the end of the main flow path to trap the cold material generated between the two injections at the nozzle end to prevent obstruction of the runner or gate. If the cold material once mixed into the cavity, it is easy to produce internal stress in the products. The diameter of cold hole is about 8-10mm and the depth is 6mm. In order to facilitate demoulding, its bottom is often carried by the demoulding bar. The top of the ejector rod should be designed as a zigzag hook shape or a depression groove, so that the ejector rod can pull out the main flow path and keep the body.

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The shunt path

It is the channel connecting the main channel and each cavity in the multi-groove mold. In order to make the molten material fill each cavity at the same speed, the distributary channels should be arranged symmetrically and equidistant on the mold. The shape and size of the shunt section have an influence on the flow of plastic melt, the demoulding of products and the difficulty of mold manufacturing. If the flow of the same amount of material, the circular section of the channel resistance is minimal. However, because the cylindrical runner is smaller than the surface, it is not good for the cooling of the shunts and the shunts must be opened on the two half die, which is not only labor and difficult to align. Therefore, trapezoidal or semicircular cross-sections of the runner are often used and are arranged on half of the mold with a stripper bar. The surface of the runner must be polished to reduce flow resistance and provide faster filling speed. The size of the runner depends on the type of plastic, the size and thickness of the product. For most thermoplastics, the shunt section width is no more than 8mm, up to 10-12mm for the largest and 2-3mm for the smallest. Under the premise of satisfying the need, the cross-sectional area should be reduced as far as possible to increase the shunts and prolong the cooling time.

That's all for the sharing,and we supply custom plastic extrusion  for sale, if you have any demand for our products,just feel free to contact us.

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