Molding Conditions of Injection Molding Machine (Part 1)

 1. Molding conditions of injection molding machine


In order to operate the injection molding machine for actual injection molding processing, it is necessary to use molding materials and molds, and complete the processing of the molded product in a state that matches the specifications of the molded product. Simply injecting molten plastic into the mold and taking it out after solidification will cause severe dimensional deviation, glossy appearance or uneven transfer of the molded product, and it is impossible to obtain a molded product with uniform quality.


In order to obtain the desired quality of injection molded products, it is necessary to adjust various parameters called "molding conditions" on the injection molding machine, and adjust the conditions while controlling the size and appearance quality to meet the specification requirements.


In other words, whether the molding conditions are adjusted well or not will affect the quality of the injection molding products produced from the mold. If the adjustment range of the condition adjustment parameter is large, the variation range of the quality specification will also increase accordingly, making the adjustment work easier. Generally speaking, when "the quality of the mold is good", it often means that the adjustment range of this condition is very large. Looking at it from another angle, it can also be said that it is very important to ensure that the molding conditions can be adjusted in a wide range in advance when designing the mold. For example, adopt a design that can sufficiently ensure the flow rate of the cooling pipeline, and carefully set the exhaust hole to ensure that even if it is filled at a high speed, it is not easy to cause trapped air to burn, etc.


Representative molding condition parameters are shown below.


(1) Resin temperature


The resin temperature can be adjusted by the temperature setting of the injection barrel. The correct setting range of the resin temperature is determined according to the grade of the resin, referring to the recommended temperature range provided by each resin manufacturer.


When it is desired to measure the actual resin temperature, a thermocouple thermometer can be used to measure by inserting the thermocouple into the injected resin.


(2) mold temperature


Mold temperature is an important parameter that affects the shrinkage of molded products and the transfer of mold cavity surfaces. Generally speaking, in the temperature range of about 15-90°C, a water-cooled thermostat is used to adjust the mold temperature. If the temperature exceeds 90°C, use a pressurized water type, oil temperature controller, or use a cartridge heater for temperature control.


Although the temperature of the mold is controlled, what really matters is the surface temperature of the cavity. In order to control accurately, the usual method is to use a contact surface thermometer to adjust the mold temperature according to the measured temperature value.


If a non-contact infrared temperature sensor is installed in the cavity, the effect will be better because it can accurately measure the mold temperature in real time, but this requires relevant equipment and professional knowledge.

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