The following are the three most common types of problems for the blow molding machine:

(1) The bottle wall is too thin. The main reason is that the preform temperature is too high and the preform stretch ratio is too large.

(2) The upper part of bottle is thin, while the bottom of bottle is thick. The reason is that the stretching speed is too slow, the blowing pressure is too high, the secondary blowing time is not suitable, the temperature of the upper part of preform is low during stretch blow molding, while the temperature of the lower part is high.

(3) The upper part of  bottle is thick, while the bottom of the bottle is thin. This is caused by too fast stretching, low first blow pressure, improper control of secondary blow time, improper control of the upper and lower parts temperatures during stretch blow molding.

Since the quality of the preform determines the quality of the finished product, so the preform must be tested. German Krones company has developed an on-line preform inspection device that can detect the concentricity, internal diameter and wall thickness distribution of the preform, and can detect 72,000 preforms per hour. The device can be installed behind an automatic palletizing station. There are many factors influencing the control of wall thickness of bottles, mainly related to the distribution of wall thickness of preforms, the performance of blowing equipment, and the quality of blowing molds, among which the wall thickness distribution of preforms is the most important. The wall thickness distribution is related to the quality of the raw material, the performance of the injection equipment, and the quality of the preform mold.
In particular, the quality of the "one-step" preform mold directly affects the wall thickness distribution of bottles.
First of all, the raw material must meet the requirements of the injection & bottle level, otherwise even the best equipment can not form a uniform thickness of the preform. Secondly, it is necessary to control factors such as injection pressure, injection molding temperature, mold core rigidity, mold accuracy, mold assembly accuracy, and parallelism between the injection mold platens. After obtaining a high-quality preform, the heating of the preform is the key to ensure uniform wall thickness. 
"Two-step" equipment is relatively easier to control the preform temperature than "one-step" four-station equipment. This is because the "two-step" preform in the heating process, combines with rotation and revolution, and the heating time is longer, so easy to make the preform temperature uniform. The “one-step” four-station preform is no rotation during the heating process, so it has higher requirements for the wall thickness distribution of the preform, and the requirements for the heating system and control performance are more restricted.

In actual production, operators often cause uneven wall thickness distribution of bottles due to improper settings in the final blowing process.

The bottle production efficiency is a very important technical indicator of the blowing equipment. What are the factors affecting the efficiency of the blowing machine?

There are several factors that affect the efficiency of a blow molding machine:

(1) Blow molding machine stretch and blow molding system;

(2) The quality of the preform, including the design of the preform, the dimensional accuracy, and the uniformity of the wall thickness;

(3) The preform heating system of the blow molding machine;

One of the main factors influencing the blowing efficiency is the solenoid valve. The accuracy, reaction time, and life of the solenoid valve of the blowing machine are very important for increasing the output. Link-Tech Machinery uses a solenoid valve specially designed by NORGREN company. Because the piston part of the valve is completely hard-sealed, its reaction time accuracy is up to one thousandth of a second and its life is up to 50 million times, thus ensuring the high blowing equipment effectiveness.

In addition, other factors that affect the efficiency of the blowing machining and assembly precision of the machine. Only the part coupled with strict precision of assembly can be able to create a stable high-speed blow molding machine.