Common quality analysis problems of plastic bottle caps

                      Common quality analysis problems of plastic bottle caps

   Plastic bottle caps in the process of injection molding, due to mold, materials and equipment and other reasons caused parts flying edge, lack of materials, and other phenomena, increase parts failure rate.Common quality problems are as follows.

4.1

Lack of material

   Generally in the plastic processing process, because the mold cavity filling is not satisfied, resulting in the shape of parts and design inconsistent phenomenon called lack of materials.

(1) equipment method

   There are many technical factors causing the material shortage of plastic parts, the most important of which is the three factors of low filling pressure, short injection time and low mold temperature.When filling pressure is low, the injection molding machine will lead to insufficient pressure in the mold cavity and the plastic will be difficult to fill the entire mold cavity, resulting in the parts missing materials.Short injection time can also lead to incomplete plastic cavity, resulting in parts missing materials;Low mold temperature will accelerate plastic solidification, reduce liquid mobility, and cause plastics to not fill the entire cavity, resulting in a lack of material.

(2) equipment reasons

   The equipment causing the material shortage of plastic parts is mainly caused by the nozzle part, which is usually blocked by the nozzle.Leakage of glue at the nozzle can also lead to material shortage.

(3) cause of mold

   Generally, the internal exhaust of the mold is not smooth, and the accumulated air in the mold cavity cannot be discharged, which will lead to insufficient plastic filling, resulting in a lack of materials. The measures taken are to reduce the filling speed of the plastics or increase the corresponding air vent on the mold.

   Due to the blockage of hot runner or imbalance of flow, the flow of plastic melt is not smooth, resulting in the lack of materials for parts. The general measures adopted are to improve the temperature of hot runner of the defective products and use delicate and clean raw materials.

4.2

flash

   The flanging usually occurs at the mold parting position, such as the mold parting surface, the joint position of the slider, the side clearance of the insert, and the pores of the push rod.When the overflow problem is not solved in time it will be expanded.The overflow from the side gap of the insert and the pore of the push rod will cause the plastic parts to get stuck on the mold and affect the mold parting.

(1) process method

   Generally due to the injection molding machine pressure or injection molding faster reasons.Due to the high pressure and high speed in the mold cavity, the tension of the mold increases, resulting in the phenomenon of overflow.The general solution is to extend the injection time and pressure maintenance time.

(2) equipment

   The machine itself does not fit properly.As a result, the mold cannot be pressed normally. Generally, when choosing the type of injection molding machine, the rated clamping force calibrated by the machine must be greater than the tension formed by the axial cross-sectional area of the injection molding part during the injection.When the mold closing device of the injection molding machine is not adjusted properly, the unbalance of the mold itself parallelism will also cause the phenomenon of flying.

(3) cause of mold

   Usually due to the unreasonable design of the mold, this problem is difficult to solve, need to redesign the mold.

4.3

shrink

  Plastic shrinkage is mainly due to the shrinkage of volume, wall thickness of the surface of raw materials are pulled in, after cooling on the surface of the finished product indentation.Shrinkage is the most bad phenomenon occurring on the surface of finished products.

(1) process method

   The injection molding machine has less injection speed and pressure keeping time, which makes the plastic parts lack fluidity. Firstly, the plastic parts entering the mold cavity are cooled faster, and there is no sufficient pressure keeping time to make up shrinkage. Generally, the solution is to adopt higher injection molding pressure.

(2) cause of mold

   The mold inside the plastic bottle cap does not discharge smoothly, also can cause the mold cavity inside redundant air cannot be excluded, the plastic that needs to retract is also less, the part shrinkage is bigger, general measure is to carry on the maintenance to the mold and increase the exhaust port.