Analysis of the design and process of the cap mold

The lack of material is generally in the plastic processing process, because the mold cavity filling is not full, resulting in the shape and design of the part does not match the phenomenon is called lack of material.

(1) Equipment method

There are many process factors leading to the shortage of plastic parts. The most important reasons are the small filling pressure, short injection time and low mold temperature. When the filling pressure is small, the injection molding machine will cause insufficient pressure in the cavity during injection molding. It is difficult for the plastic to fill the entire cavity, which leads to the shortage of parts. The short injection time will also cause the plastic to not completely fill the cavity, resulting in missing parts. The low temperature of the mold will accelerate the solidification of the plastic, and the fluidity of the liquid will decrease, which will also cause the plastic to not fill the entire cavity, resulting in a shortage of material.

(2) Equipment reasons

The reason for the equipment that causes the plastic parts to be lack of material is mainly the nozzle part, which is generally blocked by the nozzle. The general method is to clean the nozzle to solve the problem; the leakage of the nozzle can also lead to lack of material, and such a fault generally needs to be replaced.

(3) Mold reasons

Generally, due to the unobstructed internal exhaust of the mold, the air accumulated in the cavity cannot be discharged, which may result in insufficient filling of the plastic, resulting in lack of material. The measures taken are to reduce the filling speed of the plastic or to increase the corresponding row on the mold. Stomata.

Due to the blockage of the hot runner or the unbalanced flow, the flow of the plastic melt is not smooth, resulting in the shortage of parts. The general measures are to increase the temperature of the hot runner in the corresponding product and use delicate and clean materials.

The flash edge generally occurs at the parting position of the mold, such as the parting surface of the mold, the matching position of the slider, the backlash of the insert, and the pore of the push rod. When the flash problem is not solved in time, the flash edge will expand. The flashing of the insert backlash and the push rod aperture causes the plastic part to get stuck on the mold, affecting the parting.

(1) Process method

Generally caused by the injection pressure of the injection molding machine is too large or the speed of injection molding is faster. The phenomenon of flashing occurs due to the increase in the tension of the mold due to the high pressure and high speed in the mold cavity. The general solution is to extend the injection time and holding time.

(2) Equipment aspects

The machine itself has insufficient clamping force. The mold can not be properly pressed. Generally, when selecting the model of the injection molding machine, the rated clamping force of the machine must be greater than the tension formed by the axial cross-sectional area of ​​the injection molded part during injection, otherwise the mold release will be caused. Form a flash. When the mold clamping device of the injection molding machine is not properly adjusted, it will cause the mold clamping imbalance. The parallelism of the mold itself will not cause the flash phenomenon.

(3) Mold reasons

Generally, this problem is difficult to solve due to the unreasonable design of the mold, and the mold needs to be redesigned.

shrink

The shrinkage of the plastic is mainly due to the fact that the surface material at the wall thickness is pulled in due to the volume shrinkage, and a dent mark appears on the surface of the finished product after cooling. Shrinkage is the most common problem occurring on the finished surface, and most of the drywall thickness occurs.

(1) Process method

The injection molding machine has less speed and pressure holding time, which makes the plastic parts less fluid. The plastic parts that enter the mold cavity first cool faster, and there is not enough pressure holding time to carry out the feeding. The general solution is to adopt Higher injection pressure.

(2) Mold reasons

The exhaust inside the mold of the plastic bottle cap is not smooth, and the excess air in the cavity cannot be eliminated. The plastic that needs to be shrunk is also less, and the shrinkage of the part is large. The general measure is to maintain and increase the row of the mold. Air port.