Blow molding machine principle and testing items

The principle and inspection items of the blowing machine are as follows: 1. The blank supply system The blank supply system is a system that makes the PET bottles arrange and move from disorder to order. The preforms are dropped from the hopper under the action of the elevator. Due to the shape of the preform itself, the tail of the preform faces up, the head faces down, and slides forward under the action of its own gravity, and some preforms that fail to fall into the guide rail are under the action of the preform kicking device. Return to the hopper via the recovery conveyor. In this way, the remaining preforms in the guide rail are arranged in an orderly manner and enter the heating system under the action of their own gravity. 2. Heating system The function of the heating system: to heat the preform to obtain plasticity that is convenient for pressure processing. The heating system consists of lamps, reflectors, blower devices, cooling devices, etc. The far-infrared lamp in the oven radiates and heats the preform. Due to the existence of the reflective sheet, both sides of the preform are heated at the same time, and the preform moves forward and rotates at the same time, which makes the heating more uniform. A blower in the oven thermally circulates the system to make the temperature inside the oven uniform. The function of the cooling device is to cool the bottle mouth and make the bottle mouth dimensionally stable. In order to obtain a good product, the heating process is very important. It is necessary to ensure that the heating temperature is suitable and the preform is heated evenly. If the temperature is too high, the bottle may appear coking, white fog, too thin or even rupture; if the temperature is too low, it may cause local accumulation, whitening or even rupture of the bottle. If the temperature is not uniform, it may cause the bottle to deform or even break. 3. Bottle blowing system The blowing system is mainly composed of stretching device, pre-blowing device, bottle blowing device and exhaust device. The preform is mechanically stretched under the action of the stretching bar, and pre-blowing is performed while stretching, so that the bottle has an initial shape, and then the bottle is blown, and then the bottle is exhausted and taken out. The main function of pre-blowing is to make the material evenly distributed, which is convenient for blowing. 4. Auxiliary equipment The auxiliary equipment of the blow molding machine includes mold temperature machine and bottle mouth detection equipment. The mold temperature machine is used to deliver water at a certain temperature to the mold. It is heated by a heat exchanger and then delivered to the mold by a pump. There are two main functions of the mold temperature machine: (1) It is used to maintain the constant temperature of the mold and maintain the stability of the product (2) It is used to cool the bottle. After reaching the bottle mouth, it is reflected on the chip, the light is converted into voltage by the chip, and the voltage is converted into the corresponding brightness value after being processed by the CPU, thereby forming an image. If the bottle mouth is defective, the brightness value at the defect and the brightness value of other surrounding points exceed the set value. By comparison, it can be determined that this point is a defect. When the defect point exceeds the set value, the bottle is determined to be bad. bottle, the bottle will be ejected. 5. Control system The control system is mainly composed of PLC, contactor relay system, industrial computer and application software. The industrial computer controls the PLC, and then the PLC controls the contactor relay system, and then the contactor relay system drives the corresponding executive elements. 2. Description of the blowing process The working principle of the blowing machine and the bottle inspection items Preform → heating → transfer plate into the mold → stretch pre-blowing → blowing → exhaust → finished bottle Provide ②Heating: The preform is heated through the lamp tube, divided into 14 heating zones. 9 lamps in each heating zone (the number of lamps used is set according to the height of the preform). The first seven heating zones belong to penetration furnaces, and the last seven are distribution furnaces. ③ The turntable is fed into the mold: the mold temperature is generally about 65 °C, and the mold temperature is heated to about 65 °C by the water temperature machine and sent to the mold to heat the mold. ④Stretching and pre-blowing: The two steps of stretching and pre-blowing are carried out at the same time. The stretching is mainly carried out by the stretching rod, and the preform is pulled to a certain extent. Pre-blowing is to pre-blow the preform through a low pressure of 8-13bar. ⑤Blowing: blowing into bottles through high pressure of 36-40bar. ⑥ Exhaust: Exhaust the high pressure gas in the mold. ⑦Finished bottle: 3. The main test items of the bottle are weight, cold capacity, top pressure, bottle outer diameter (shoulder diameter, bottle body diameter, heel diameter, bottom ring diameter), bottle height, bottle mouth specification, thickness (upper diameter) Shoulder thickness, mid-shoulder thickness, sidewall thickness, heel thickness, thickness near bottom center), drop performance and appearance. Appearance: Mainly include flat end face of bottle mouth, complete thread, flash, intact support ring, coking, mold sticking, scratches, air bubbles, water marks, white fog, color, uncleanness, good molding without rigid material, Sink, turn out, crack, core shift, etc.
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