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The analysis and solution of the two-step blowing process principle

Update:29-05-2020

At present, high-end bottles on the market are generally blown by a two-step method. The two-step method is deliberately carried out in two steps, also known as injection and blow molding. The embryo is blown into a bottle.

Because preforms are used to process blown bottles, the quality of the preforms is very important.

Usually, several problems easily occur during the blowing process. Blow the bottle, gather the bottom material, the bottom is not correct, the bottle is thin, the bottle is whitish, etc. How to distinguish between the problem of blowing and the problem of preforms. Now we analyze from the different conditions on the blown bottle;

1. The reason for the bottle blowing:

1. The embryo tube is not heated enough and is not fully baked;

2. The stretching rod is not pulled into place (in the end);

3. The speed of the stretching rod is too slow;

4. The temperature protection is turned on but the upper and lower temperature limits are set too high.

Solution:

1. Increase the voltage when the output is unchanged. When the voltage is constant, the output is reduced, that is, the time of the second blowing is increased.

2. Exhaust after closing the mold, push the stretching rod to the bottom of the mold and touch the bottom of the mold by hand, and tighten the limit nut. (Only limited to mechanically limited cylinder adjustment).

3. Adjust the throttle valve on the stretching cylinder to the maximum.

4. Lower the lower limit temperature, the general PET preform is set to 85 ~ 95 degrees, and the upper limit can be set to 125 ~ 130 degrees.

Second, the bottom aggregate, that is, there is a thick material at the bottom together:

1. Generally, the delayed blowing time is too long, or one blowing time is too long;

2. The bottom of the preform is not baked soft, and the temperature difference with other locations is large.

Solution:

1. To reduce the time of delayed blowing, the general dosage is about 0.3 seconds, which can be increased or decreased according to the bottle condition.

2. Pinch the embryo tube by hand to see if the bottom is still very hard. If so, increase the voltage of the corresponding bottom tube.

3. The reason for the bottom error:

1. The speed of the stretching rod is too slow;

2. The delayed blowing time is not enough;

3. The preform is severely eccentric.

Solution:

1. Adjust the throttle valve on the stretching cylinder to the maximum;

2. Increase the delayed blowing time;

3. Measure the eccentricity of the embryonic tube. (When the eccentricity is large, the embryonic tube will become curved when heated to a certain extent);

4. Including temperature protection items.

Fourth, the reason for the bottle body bias:

1. If the water level at the bottom of the bottle is centered, the embryo tube may be more eccentric, or the cooling water of the injection mold

Road is related, uneven cooling.

2. There are some places where the embryo base does not rotate.

Solution:

1. Try another cavity embryo tube test, change injection mold or injection molding process.

2. See if there is any embryo seat that has not rotated. If found, adjust the rotation chain to all embryos in the heating zone

The seats are turning.

5. Reasons for the bottle whitening:

1. The voltage is too high, and the bottle is white or ceramic all around or partly.

2. The voltage is not enough, resulting in no baking, and the bottle is pearly white or partly. The voltage is too high to reduce

Voltage, if the voltage is too low, increase the voltage.

6. For the double-cavity machine, the time when the two stretching rods are pulled to the bottom should be adjusted to the same

This can be adjusted on the throttle. Under the condition that the quality of the preform is qualified and stable, the different conditions of the two bottles blown out can determine how to adjust.

1. The bottles in cavity A blow very well, and the bottles in cavity B are blown out, it is possible that the stretching rod in cavity B is slow, and the adjustable B

The throttle valve on the cavity stretch cylinder.

2. The bottles in cavity A are blown very well, and the bottom of the bottles in cavity B has a material accumulation, but the stretching rod of cavity B is too fast.

Reduce the throttle of the B-chamber stretch cylinder.

Seven, according to the different circumstances of the bottle to identify where the problem is caused, the broken bottle, eccentricity or other problems

Check some or all of the bottles with the same problem to see if they are the same blow cavity number, or not the same injection cavity number, whether it is in the same position of the injection cavity or the same position of the blow cavity, if it is in the injection cavity At the same position, for example, every time there is a problem with the No. 2 embryo tube, it means that the No. 2 cavity embryo tube has a problem. To find the difference. See if each defective product has common features. From these common points to find and distinguish what is the problem. Requisition and resolve.

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The analysis and solution of the two-step blowing process principle
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