A good forming condition is judged by the following criteria: whether the production process is stable or not and whether there is maximum efficiency. In the process of forming, many times there will be produced for some time, the product will be burnt, lack of glue and other harmful appear, to exclude these problems and achieve production stability, forming parameters in the material temperature, mold temperature and the interaction between the cycle must be mastered.
The material is driven by the rotation of the screw at the lower material port and is pressed into the barrel. While entering the barrel, it is heated, melted, and pressed from the end of the barrel to the front end, and this process turns the material into a high-temperature, high-pressure fluid. Then by the thrust of the screw, the molten material is injected into the mold, and in the mold, the final product comes out by cooling and shaping.
What are the main factors that will be influenced in this process? Pressure, speed, time, and temperature are the main factors, mainly talking temperature. In material from solid to fluid and then to solid, the temperature change is enormous, generally from the material drying temperature (80° to 140°) to the forming temperature (200 to 400). Then to the demolding temperature (mold temperature and material decision), in this process, the barrel temperature, mold temperature, and cycle are involved together to come up with qualified products.
Each material has a range of temperature requirements, and within that range, how much do we use as the best? Temperature is energy, the material from solid to fluid, from low temperature to high temperature, absorbs heat, fluid to solid, from high temperature to low temperature, and exothermic.
Because forming is a regular cycle of the process, according to the law of conservation of energy, the heat between the two cycles must be balanced, that is, in the average production of how much heat is absorbed (barrel heating), in addition to the consumption (cooling) of heat, how much heat should be released, to achieve conservation of energy.
Whether it is heat absorption, heat consumption, or heat release, it takes time and also needs the efficiency per unit of time, which is the problem of the cycle and the efficiency of heat transfer, so, starting from the cycle and heat transfer, can solve a lot of problems.
Temperature Heating and cooling are required time. If the temperature is not balanced, the temperature (including material temperature/mold temperature) in each cycle of the residual will be left to the next cycle, cumulative, the back of the product temperature will be high up, bad appear. Low temperature will be added in each next cycle for the last less temperature, and cumulatively, the temperature will be lower and lower, and the defect will appear. So what is the way to control the temperature to reach a balance?
The production temperature depends on 3 factors:
1. The original heat source.
3. Cooling speed.
The heat source is the material temperature we set (mold temperature is the cooling medium), and the high or low setting directly affects the amount of heat transferred.
Time is mainly the cycle time. Each cycle can reach a balance between the cycle is very important to the fast and slow.
The cooling rate depends on the size of the temperature difference. That is the temperature difference between the material and the mold. The lower the temperature difference, the slower the cooling rate, and the larger the temperature difference, the faster the cooling. The use of different temperatures in the mold is to change the cooling rate of the material in the mold so that the appearance and size can meet our requirements. The different cooling rate of the material inside the mold has different performance on the stress, shrinkage, and stretching of the mold, which is reflected by cracks, whitening, deformation, shrinkage, etc.
The setting of mold temperature is related to the material and mold. Different materials and molds have different suitable mold temperatures, set according to the actual situation. If the mold does not dissipate heat sufficiently, the mold temperature will rise slowly, changing the cooling speed, cooling efficiency decreases, and the cycle lengthens.
Mold temperature, material temperature, cycle, and the interaction of these 3 aspects, the balance, will be able to achieve one of our requirements: production stability and efficiency maximization. How these 3 aspects interact and control each other requires experience and technology. The basic is that the cycle is fixed according to the bad condition to decide the mold temperature and material temperature.
For example, the lack of rubber may be the material temperature is not enough, the injection speed is not stable, and it may be too high material temperature, resulting in material fluidity, injection reflux caused by. Some products become poor in size production. Also, the temperature is not well balanced.
Of course, to have a perfect condition takes more than these 3 points. There are many. This is just a general requirement and the basic requirements for the tuning machine to understand.