At present, most blow molding machines are still two-step blow molding machines, that is, plastic raw materials are made into preforms before the blowing is completed. Today, the same ordinary and ordinary environmentally friendly plastics made of polyester materials are used.
1. Bottle blowing affair
The blowing process of the bottle blowing machine is divided into two parts
1, warm up
Using the process infrared high temperature lamp to irradiate the preform (preform), heating and softening the damaged (preform) part of the preform (preform). In order to maintain the shape of the bottle mouth, the preform (blank) mouth does not need to be heated, so a certain cooling device is required to complete the cooling control.
2, blow molding
At this stage, the preheated preform (preform) is discarded into the blow mold, and high-pressure inflation is completed internally. Blow the preform (blank) into the desired bottle.
The automatic bottle blowing machine completes the two clamping of the bottle blowing through the clamping of the process manipulator, eliminating the need to manually put the preheated preform into the middle blow mold. The delivery speed is greatly accelerated.
2. The process flow of the bottle blowing machine
The blow molding process of the bottle blowing machine is a two-way stretching process. The polyester chain is bi-directionally stretched and oriented, which improves the mechanical properties of the bottle wall, improves the tensile, tensile and impact strength, and has good air tightness. Although stretching helps to increase the strength, it should not be overstretched. The ratio of stretch to expansion should be controlled: the radial direction should not exceed 3.5 to 4.2, and the axial direction should not exceed 2.8 to 3.1. The wall thickness of the preform should not exceed 4.5 mm.
bottle blowing ends between the glass transition temperature and the crystallization temperature, which is also controlled between 90-120 degrees. In this interval, the polyester is in a highly elastic state and becomes a transparent bottle after rapid blow molding, cooling and solidification. In the one-step method, the temperature is determined by the cooling time in the injection molding process (such as the Aoki bottle blowing machine), thereby connecting the injection and blowing stations.
In the blow molding process, there are: stretching-one blow-two blows. These three actions take a short time, but they must be very good together. In particular, the first two steps determine the overall distribution of the material and the quality of the blown bottle. Therefore, it is necessary to recover well: stretching start opportunity, stretching rate, pre-blowing start and end opportunities, pre-blowing pressure, pre-blowing flow rate, etc. If possible, control the temperature distribution of the entire preform and the temperature gradient between the inner and outer walls of the preform.
In the rapid blow molding and cooling process, the bottle wall will produce induced stress. For carbonated beverage bottles, it can resist internal pressure and is beneficial, but for hot-filled bottles, it guarantees complete release above the glass transition temperature.
Three, plasticizing system debugging
1) The heater of the plasticizing system is evenly tightened, and the heater is closely and evenly attached to the heated surface. For the mica heater, tap lightly with a rubber hammer when tightening to ensure a tight fit, which is beneficial to uniform heating and prolongs the service life of the heater.
2) The thermocouple probe has enough spring preload to ensure accurate temperature measurement.
3) The compression bolts of the cylinder die head should not be completely tightened, but should be lightly tightened to leave room for expansion and contraction of the cylinder. The axis of the barrel should remain straight and not bend.
4) Be sure to turn on the barrel cooling water and mold cooling water before heating to prevent blockage and blockage of the barrel feed section, and prevent the gearbox and the cylinder seal on the mold from aging and leaking too fast.
5) A magnetic rack needs to be placed in the hopper to prevent iron filings and debris from entering the screw, causing damage to the screw and mold components or blockage of the mold flow channel.
6) When the cooler is started, it is usually recommended to reduce the extrusion speed and gradually increase the speed after the tube is normally extruded from the die.
7) Before the tube blank is normally extruded from the die, personnel should not stand in front of or under the die; during the first three injections of the gas cylinder machine, personnel should stay away from the bottom of the mold, and the manual injection pressure should not be too high (generally not More than 5mA).
8) The automatic injection pressure of the gas cylinder machine should not be too high. The actual time for automatic shooting usually exceeds 5 seconds. Too fast speed can easily lead to inaccurate wall thickness tracking and melt fracture.
9) For machines equipped with a wall thickness control system, the wall thickness controller should be started and operated manually, and then the extrusion should be started to prevent the mold opening from being completely closed and damaging the parts.More about: chain Water Bottle Blowing Machine 7500BPH