The tail and branch head
fishtail type head of simple structure, easy fabrication, can be used in a variety of plastic extrusion molding, such as polyolefin plastics, PVC and polyformaldehyde, etc. But in this way the production of plate and sheet of generally less than 500 mm in length, thickness of less than 3 mm, therefore not suitable for extrusion wide sheet. Fish tail type head tail expansion Angle usually take 80 & deg; The left and right sides. Branch pipe type nose cavity for the tube, a longitudinal incision and mouth area.
if plastic low viscosity, good fluidity, high molding temperature, the width of small plastic, can adopt a branch pipe forming, if plastic viscosity is high, the sheet is wide, you must want to use two branch pipe forming. Screw head is also called the screw head distribution type, similar to branch pipe type head, is the main difference between the screw inserting a screw root distribution in the nose. Screw driven by motor rotation, can undertake the infinite speed, so the material will not stagnation in the tube.
the pipe head exactly parallel to the tubular cavity with the mouth, can store a certain amount of material, and make the material flow into the die cavity stability and wide plastic extrusion evenly. The tube head is characteristic of the nose is small in size, light weight, simple cavity structure, temperature control and easy manufacturing process more easily. Branch pipe type head can molding plate and sheet width and larger width can be adjusted, in polyethylene, polypropylene, polyester, etc plate and sheet are using this head extrusion molding.
the nose of the type of branch pipe is characterized by simple structure, can adjust width, can produce wide products. Suitable for polyethylene and polypropylene plastics extrusion molding. Head straight pipe type of defect is material stay in the tube for a long time, easy to decompose discoloration, temperature control difficult. Intermediate feed type bending pipe cavity to streamline the nose, no dead Angle, suitable for the thermal stability of plastic molding, but the nose manufacturing difficulty, width cannot be adjusted.
the nose cavity is similar to the tail shape, molten material from the central head into the cavity, to both sides, in the place out of the mouth has a certain width and thickness of plate and sheet. Due to the material in the inlet pressure and flow rate is greater than on both sides of the nose, and because both sides than the middle heat faster, so the material viscosity increases, cause central discharging, on both sides of the discharging, extrusion plate and sheet thickness is not uniform. To avoid this problem, to obtain the thickness uniformity of plastic injection molding processing, usually in the nose cavity choke or choke rod is installed inside, to increase the flow resistance of the material in the middle of the nose cavity, adjust the size of the mold cavity material flow resistance, flow velocity on the length of the material in the mouth mould are equal, the pressure evenly.
double branch pipe with a choke rod head wide plastic parts for processing high melt viscosity. Choke rod is used to regulate traffic, limiting cavity in the middle of the plastic melt flow rate, wide plate and sheet thickness uniformity, forming width is 1000 - 2000mm。 The disadvantage is that the plastic melt in the nose pipe die cavity to stay for a long time, easy overheating decomposition, so is suitable for heat-sensitive plastic, but it sometimes can be shorten branch pipe diameter and die flow length to improve them.
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