Blowing Machine Working Principle

A blow molding machine is a device used in plastic production that uses thermoforming technology to blow pre-heated plastic preforms into bottles. The bottle blowing machine includes an embryo supply system, heating system, bottle blowing system, auxiliary equipment, and control system.

1. Embryo Supply System

The embryo supply system is a system that uses PET bottles to arrange and move from disorder to order. The embryos fall from the hopper into the guide rail under the action of the elevator. Due to the shape of the embryos themselves, the tail of the embryos is upward and the head is downward, and they slide forward under the action of their own gravity. Some of the embryos that fail to fall into the guide rail return to the hopper through the recovery conveyor belt under the action of the embryo kicking device. In this way, the preforms in the guide rails are arranged in order and enter the heating system under the action of their own gravity.

2. Heating System

Function of the heating system: to heat the preforms to make them plastic enough to be pressed. The heating system consists of lamps, reflectors, blowers, cooling devices, etc. The far-infrared lamps in the oven radiate heat to the preforms. Due to the presence of the reflectors, both sides of the preforms are heated at the same time. The preforms move forward and rotate at the same time, making the heating more uniform. The blower in the oven circulates the system to make the temperature in the oven uniform.The function of the cooling device is to cool the bottle mouth and make the size of the bottle mouth stable. In order to obtain a good product, the heating process is very important. It is necessary to ensure that the heating temperature is appropriate and the preform is heated evenly. If the temperature is too high, the bottle may become coked, white fogged, too thin or even cracked; if the temperature is too low, it may cause local accumulation of material in the bottle, whitening or even cracking. If the temperature is uneven, the bottle may be deformed or even cracked.

3. Bottle Blowing System

The bottle blowing system is mainly composed of a stretching device, a pre-blowing device, a bottle blowing device, and an exhaust device. The preform is mechanically stretched by the stretching rod, and air is pre-blown at the same time to give the bottle an initial shape before blowing. Finally, the bottle is exhausted and taken out. The function of pre-blowing is to make the material evenly distributed and facilitate bottle blowing. The shape of the pre-blowing bottle directly determines the difficulty of the blow molding process and the performance of the bottle. The normal shape of the pre-blowing bottle is spindle-shaped.

4. Auxiliary Equipment

The auxiliary equipment of the high-speed blow molding machine series includes mold temperature controller and bottle mouth detection device

The mold temperature controller is used to deliver water of a certain temperature to the mold. The water is heated by a heat exchanger and then delivered to the mold by a pump. The mold temperature controller has two main functions:

1)  Used to maintain constant temperature of mold and maintain product stability

2)  To cool bottles

Brief working principle of the bottle mouth detection device: The light emitted by the light source in the digital camera hits the bottle mouth and then reflects onto the chip. The light is converted into voltage by the chip, and the voltage is converted into corresponding brightness value after being processed by the CPU, thus forming an image.If there is a defect at the mouth of the bottle, the brightness value at the defective part of the bottle exceeds the set value with the brightness values of other parts around it. By comparison, it can be confirmed that this point is a defect. When the defect point exceeds the set value, it is determined that this bottle is a bad bottle and 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 PL, and then the PLC controls the contactor relay system, and finally the contactor relay system drives the corresponding actuators.