Blow Mold Management: Daily Maintenance, Common Problems, and Solutions

Blow Mold Management: Daily Maintenance and Troubleshooting

During production, blow molding machine molds will inevitably suffer some wear. Therefore, daily maintenance of blow molding machine molds is required. Blow molds need proper maintenance to preserve the quality between the machinery and raw materials, which helps the normal progress of blow molding work.

I. Precautions for Daily Maintenance of Blow Molds

1. In the production of extrusion blow molding hollow products, frequent mold opening and closing actions make the guide pillars, guide sleeves, guide rods or guide rails in the mold very easy to wear. During each shift, it is necessary to frequently check whether the lubricating oil at this position is sufficient and clean, and remove dirt and replenish enough lubricating oil in time. Severely worn parts should be repaired and replaced in time, otherwise it will affect the accuracy of the mold closing position and also lead to unqualified blow molding products.
2. The blank clamping port often cuts off the excess material edges in blow molding products. Although the cutting edge is made of alloy tool steel, long-term work will also cause wear. When necessary, the mold maintenance worker will grind it.
3. The inner surface of the cavity, according to the appearance quality requirements of the product, some need sandblasting treatment; some need polishing and require high brightness to ensure the transparency of the product. After long-term work, volatile substances in the raw materials adhere to the surface, affecting product quality, so the cavity surface should be polished in time using polishing agent and cotton cloth until the surface is as bright as a mirror.
4. The shear block at the neck of the hollow container and the shear sleeve of the air inlet rod are the main devices to ensure the quality of the product neck. When wear occurs, it should be repaired in time, and the part should be replaced if necessary.
5. The stability of the temperature control of the forming mold and the rationality of the temperature control of each part have a great impact on the product quality. Regularly check whether the cooling circulation water hole is unblocked. If necessary, descaling agent can be used for cleaning, and then clean water can be used to wash away the dirt.
6. If the mold is not used for a long time, all parts of the mold should be cleaned, the dirt in the guide sleeve and circulation water hole should be blown out with compressed air, then a layer of protective agent should be applied, the two half molds should be closed, and stored in a dry and ventilated place. No heavy objects are allowed to be placed on the mold body to prevent deformation.
7. For blow molded transparent containers, the cavity of the blow mold that needs high polishing should be polished once every period of time during the production process. Use polishing agent and soft cotton paper to polish the mold cavity, rub hard to make a small amount of polishing agent penetrate into the surface, and then use clean cotton paper to polish until the mold cavity appears as a mirror.
8. When the cooling hole of the blow mold is blocked or corroded and affects the flow of cooling medium, it should be cleaned immediately. The guide pillar and guide sleeve of the blow mold should be lubricated regularly, and replaced at least once a year to ensure alignment and improve mold life.

II. Common Problems and Solutions

Problem 1: Wall Thickness Variation

The wall thickness of the bottle changes from thick to thin, for example, from the shoulder to the middle section, or from the bottom to the middle section.

Solutions:

1. Check whether the high-pressure filter on the side of the mold is unblocked to avoid affecting the supply of high-pressure gas.
2. Check the working condition of the air path valve to ensure accurate positioning during blowing.
3. Check the air flow control components of the blowing to ensure correct set values and smooth internal flow without blockage.
4. Ensure that the blowing can be completed in the shortest time, otherwise additional cooling will be brought to the PET material.
5. Ensure that all ventilation holes on the mold are not blocked.

Problem 2: Expansion in the Screw Area

Expansion of the screw area conducted to the anti-gas groove, more serious in hot weather due to high temperature during the bottle blowing process.

Solutions:

1. Adjust the position of the cooling plate so that it can provide stronger protection to the thread area of the preform.
2. External cooling can be used to control the temperature of the thread area and mandrel of the preform when it passes through the oven.
3. Excellent design of the cooling plate may be the best countermeasure.