How to deal with the insufficient filling of injection molded parts
Injection molding processing from plastic particles to molding injection molding products needs to go through a series of rigorous processes, and the lack of mastery of any process in the middle will lead to product quality problems, which are shared as follows.
1. Rheological mechanics of plastics: how plastics flow, orient and change viscosity
2. The purpose, operation and results of temperature, pressure, speed and cooling control
3. Multi-stage filling and multi-stage pressure holding control; Crystalline, amorphous, and molecular/fiber orientation effects on process and quality
4. How does the adjustment of the setting of the injection molding machine affect the process and quality
5. The influence of internal stress, cooling rate and plastic shrinkage on the quality of plastic parts
Improper feed adjustment, lack of material or too much.
Material shortages can be caused by improper feed measurement or improper operation of the feed control system, abnormal injection cycle due to limitations of the injection molding machine or mold or operating conditions, low preform back pressure or low particle density in the barrel. For particles with large particles and large porosity, plastics with large changes in crystallinity ratio, such as polyethylene, polypropylene, nylon, etc., and plastics with large viscosity, such as ABS, etc., should be adjusted when the material temperature is high, and the amount of material should be adjusted.
When there is too much material stored at the end of the cylinder, the screw will consume the injection pressure beyond the amount to compress and push the excess material stored in the cylinder during the injection process, thereby greatly reducing the effective injection pressure of the plastic entering the mold cavity and making the product difficult to fill.
The injection pressure is too low, the injection time is short, and the plunger or screw returns too early.
Molten plastics have high viscosity and poor fluidity at low temperatures, so high-pressure and high-speed injection should be used. For example, in the manufacture of ABS colored parts, the high temperature resistance of the colorant limits the heating temperature of the barrel, which should be compensated by a higher injection pressure and longer injection time than usual.
The temperature of the material is too low.
The temperature of the rear end of the cylinder is low, and the melt entering the mold cavity rises to the extent that it is difficult to flow due to the cooling effect of the mold, which hinders the filling of the remote mold; The low temperature and high viscosity plastic flow difficulty at the front of the barrel hinders the forward movement of the screw, resulting in a sufficient pressure indicated by the pressure gauge, but the melt enters the mold cavity at low pressure and low velocity