Common Problems In Blow Molding Machine And Their Solution

15-12-2021

Most companies depend so much on the blow molding machine for the manufacturing of packaging material for their items. As this is typically genuine, so many companies too confront a lot of issue, a few of which may got to do with the quality of bottles they are having from their bottle blowing machine.

This article helps to identify two of such common problems as well as ways in which these problems can be tended to without too much stress.

bottle blow molding machine

1. Drop-impact failure

Routinely, a PET bottle expected to  contain water at almost 4°C ought withstand a fall from a height of around 4-5 feet in line with the condition inside a household fridge. Compared to polyofins, which may be destroyed,  indeed PET bottles does not undergo any breakage around the thinnest corner except in the condition of cloudiness or pearlescence.

In such situation,  the PET bottle may have a small scratch but will not break because it is well-oriented even around the slender spot. So, it then follows that where this knowledge is lost, the bottle failure can not be escaped.

This is usually found in some custom-made bottles where there is ordinarily a small scratch proportion, and it is common among bottles created through a single-stage molding.

In a two-stage molding, which is mostly acceptable, the performance of the bottle will be  enhanced as a result of a cooler preform temperature that will exert more knowledge on the PET material utilized  for the manufacturing of the bottle.

On the other hand, hold-time or cooling should be figured in, in a single-stage production process, as this will upgrade the cycle time of the material. Interestingly, the cooling or hold time has a positive effect in the sense that it enables the preform material to shrink far away from the center in the process of cooling and this makes the process acceptable by many.

However, this makes crystalline zones more brittles and susceptible to failure when the preform material is overheated to the point where haze sets in.

 

2. Pearlescence and haze

Pearlescence and haze are two opposing issues that will both be exceptionally cumbersome to differentiate, and they both contribute to the whitening of PET bottles amid blowing while utilizing a bottle blowing machine. Because of  some unwanted stress placed on PET material amid the process of blowing, pearlescence is ordinarily referred to as stress-whitening.

The PET bottles microstructure can effortlessly break up, particularly when they are overstretched, which will form a little white circles around the wall of the bottle. This is  precisely where the name pearls exist from.

Overstretching of a PET bottle is more often caused by both the thickness of the material utilized and the temperature of the bottle blowing machine. This implies that a PET preform with a slender wall revealed to a low temperature a little above the glass-transition point is likely to do well compared to a thicker bottle revealed to a low temperature, because it will surely undergo pearlescence.

Pearlescence on PET bottles are more often experienced around the inside of the bottle, in most cases, since this portion are opened to a higher stretching force. In understanding this, it will be easier to solve this kind of issue without encountering any down time in your production process.

bottle blow molding machine

In a condition whereby, the affected area is a bit thin, then it implies that such area ought to be cooled whereas the following area beneath it heated for the intention of channeling more material towards the whitish region of the PET bottle. For a circumstances whereby  the white area is thick, it at that point implies that the by and large temperature should be expanded for the reason of permitting the bottle to stretch without hassles.

From another point of view, either at the stage of blowing or amid the injection stage, haze is shaped on a PET bottle, particularly, when either of these stages are carried out over a temperature of 240oF (115oC), and after that permitted to cool for just a brief period of time. At such a high temperature, it becomes exceptionally easy for PET molecules to form crystals because they have high level of freedom, which is a result of a lower energy state at the moment.

When carrying out a two-stage blowing, it is suggested and vital that the temperature be brought down or should permit more ventilation into the chamber so as to bring down the temperature of the preform material below 240oF (115oC).

Subsequently, haze is more often experienced around the exterior of the preform material, and being exposed to adequate ventilation will be sufficient to cool the exterior portion than the interior. For a single-stage process, hold time or cooling should be raised to take care of haze on the bottle.

 

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