Knowledge about the injection process
一、Temperature control
1、Cylinder temperature: injection molding process demand control barrel temperature, mold temperature and nozzle temperature. The main impact of the first two temperature plastics and plastic flow, the latter mainly affects temperature plastic flow and cooling. Each has a different kind of plastic flow temperature, with a plastic, due to different sources or trademarks, its flow temperature and decomposition temperature is different, it is due to the average molecular weight and molecular weight distribution due to different types of plastic stand in plastics injection molding machine, the process is different, and thus select a cylinder temperature is not the same.
2、Nozzle temperature: nozzle temperature is generally slightly lower than the maximum temperature of a cylinder, which is to prevent the melt in the straight-through nozzle may occur "salivation appearance." Nozzle temperature is not too low, otherwise it will form the early melt and pour nozzle clogging, or due to early condensate material into the mold cavity and affect the function of the finished product.
3、Mold temperature: mold temperature great impact on the intrinsic features and apparent quality of the finished product. Mold temperature is decided whether the plastic crystalline, scale and structure of the finished product, functional requirements, and other technical conditions (melt temperature, injection rate and injection pressure molding cycle, etc.).
二、Pressure Control
Contain plastics injection molding process pressure and injection pressure of two pressure and a direct impact on product quality plastics and plastics.
1、Plasticizing pressure :( back pressure) using a screw type injection machine, the top of the melt in the screw when the screw is rotated backward the pressure on called plasticizing pressure, also known as the back pressure. The size of such pressure can be achieved through a relief valve in the hydraulic system to adjust. Injections, the size of the plasticizing pressure is with screw speed is unchanged, adding that progress will melt temperature plastics pressure, but will reduce the speed of plastics.
In addition, adding the plasticizing temperature of the melt pressure often make uniform and homogeneous mixing toner melt discharge gas. In normal operation, the pressure should be decided plastics guarantee excellent product quality under the premise as low as possible, the specific values are used in plastics with different varieties, but usually less than 20 kg / cm.
2、Injection pressure: in current production, almost all of the injection pressure to the plunger injection machine are plastic screw top or by the pressure (by conversion to the line pressure) of the subject. Injection pressure in injection molding role is to overcome the plastic flows from the barrel cavity flow resistance, given the rate of melt filling and compaction on the melt.
三、Molding cycle
Injection molding process required to complete a moment, said molding cycle, also known as the molding cycle. It contains the following sections practice: the molding cycle: molding cycle directly affects labor productivity and equipment utilization. Therefore, in the production process, should be under the premise of guaranteeing quality, shorten the molding cycle of each relevant time. Throughout the molding cycle, injection time and cooling time to the most important, the quality of the finished product that they have a decisive impact. Moment of injection mold filling time directly and inversely proportional to the rate of filling, filling the production time is usually about 3-5 seconds.The dwell time of injection time is the pressure of the cavity plastic moment in the entire greater proportion of injection time, usually about 20-120 seconds (special thick parts up to 5 to 10 minutes). Before the gate to melt frozen, how much pressure retention time, the accuracy of the finished scale impact, if in the future, was not affected. Dwell time is also the most favorable value, which is known to depend on the melt temperature, mold temperature and the size of the main channel and the gate. If the scale and technical conditions of the main channel and the gate is normal, that is usually drawn finished shrinkage scale fluctuations minimal pressure values prevail.Cooling time depends mainly on the thickness of the finished product, the plastic heat function and crystallization function, and mold temperature and the like. The end of the cooling time, in order to ensure that the finished product should not cause changes in release when the principle of the cooling time is typically between about 30 to 120 seconds, the cooling time is too long is not necessary, not only to reduce the production efficiency, complicated parts will stripping difficult to form, and even cause stress forcibly stripping stripping. Other molding cycle time of the production process is continuous and the degree of automation and continuous and automation related.