Selection and disassembly of screw of injection molding machine


How to decide the screw of injection molding machine In […]

How to decide the screw of injection molding machine
In order to avoid material storage, there is no check ring, and the head taper is 20 ° - 30 °. It is more suitable for soft glue. If the product demands higher requirements, the non metering section and separated screw can be used. This screw is more suitable for hard PVC. In addition, in order to cooperate with temperature control, cooling water or oil holes are added inside the screw in the feeding section, cold water or oil tank are added to the cylinder, and the temperature control accuracy is close to 2 ℃.
How to decide the screw of injection molding machine: parameters
L / D refers to the length diameter ratio of the screw, l is the effective length of the threaded part of the rod. Under the condition of a certain diameter, the larger the length diameter ratio is, the longer the thread length is, which directly affects the thermal process of the material in the rod and the ability of connecting pipe energy; if the L / D is too small, it directly affects the melting effect and melt character of the material; if the L / D is too large, the transmission torque increases and the energy consumption increases.
L1 refers to the length of the feeding section and L1 should guarantee that there is sufficient conveying space for the materials, because too short L1 will lead to premature melting of the materials, so it is difficult to guarantee the conveying conditions of firm pressure, and it is also difficult to guarantee the plasticizing character and plasticizing ability of the screw in the following sections.
H1 refers to the depth of screw groove in the feeding section. If the depth of H1 is deep, it will contain more materials, improve the feeding capacity and plasticizing capacity, but it will affect the plasticizing effect of materials and the shear strength of the screw root. Similarly, it is common H1 ≈ (0.12-0.16) d
L3 refers to the length of melting section. The length of L3 is conducive to the fluctuation of melt in the screw groove, with firm pressure impregnation, so that the material is repelled from the screw head with a uniform amount of material, similarly ordinary L3 = (4-5)
How to decide the screw barrel of injection molding machine: PMMA (plexiglass material)
A. L / D selects the mutation type with the length diameter ratio of 20-22, depending on the accuracy of the product forming, it demands the same ordinary Li = 400%, L2 = 40%.
B. Compression ratio: 2.3-2.6.
C. In view of its hydrophilicity, the front end of the product adopts the mixing ring structure.
D. The other parameters are also ordinary, which can be planned according to the process screw, and the gap between them is too large.

How to dismantle the screw of injection molding machine
The appearance of the screw used in the injection molding machine and the extruder is very similar. They are all cylindrical thin and long threaded rods with thread grooves. According to the thread type, there are two types: the mutation type of equal distance and unequal depth and the mutation type of thread depth changing from deep to shallow. Special tools shall be used for screw device of injection molding machine, and heavy hammer shall not be used for knocking. The specific device steps are as follows.
① Device nozzle and connection between nozzle and barrel.
② Separate the rear key connection from the drive shaft.
③ Connect the flange of the device and move the screw forward.
④ When the head is exposed from the barrel, immediately install the connecting thread (steady: the thread here is also ordinary, mostly left-handed).
⑤ Check ring and sealing ring on the screw rod of the device.
⑥ The nozzle, check ring and sealing ring on the device shall be cleaned immediately with copper brush and shovel tools when they are hot. In addition, the cat material that is difficult to clean shall be heated in the oven at the lowest temperature that can soften the material, and then the residual material shall be eliminated.
⑦ Assemble all parts together, and apply molybdenum disulfide heat-resistant grease to all threaded connection parts, so as to facilitate the next device.
⑧ After cleaning the outside of the temporarily inconvenient photographing rod, it shall be coated with protective oil, wrapped and hung at the safety place in the side view.