The preform is filled into the mold of the mold by inje […]
The preform is filled into the mold of the mold by injection molding at a specific temperature and pressure, formed under the working conditions of the injection molding machine, and is formed into a semi-finished product of the intermediate preform mould by injection molding, and then processed into a terminal product through blow molding.
The preforms of the preforms are generally more numerous, and the product requirements are relatively high, otherwise the wall thickness of the bottle that is blown out is not uniform.
Before choosing a preform mold, you must first understand how big your injection molding machine is, how much weight the bottle can be used, and how many milliliters and how many grams you need to blow out.
Since PET has a stable time after melting point and a high melting point, it is necessary to use an injection system with more temperature control sections and less self-friction heat during plasticization, and the actual weight of the product (aqueous mouth material) cannot be less than the machine injection. 2/3 of the amount. Based on these requirements, Ramada has developed a small and medium-sized series of PET plasticizing systems in recent years. The clamping force is selected to be greater than 6300t/m2.
Mold and gate design
The PET preform is generally formed by a hot runner mold. It is preferable to have a heat shield between the mold and the injection molding machine template. The thickness of the preform is about 12 mm, and the heat shield must withstand high pressure. Exhaust gas must be sufficient to avoid local overheating or chipping, but the depth of the exhaust port should not exceed 0.03mm, otherwise it will easily produce flash.
It can be measured by air-to-air method. Between 270 and 295 ° C, the enhanced grade GF-PET can be set to 290-315 ° C and the like.
Generally, the injection speed is fast, which prevents premature coagulation during injection. But too fast, the high shear rate makes the material brittle. The shot is usually completed in 4 seconds.
The lower the better, to avoid wear. Generally no more than 100bar. Usually no need to use.
Do not use excessive residence times to prevent molecular weight degradation. Try to avoid temperatures above 300 °C. If the shutdown is less than 15 minutes. Only need to be air-blasted; if it is more than 15 minutes, clean it with viscosity PE and reduce the temperature of the barrel to PE temperature until it is turned on again.