According to the top blow molding manufacturers, equipment failures happen. Fortunately, there are viable reasons and remedies for each failure. Although there are more than three possible issues, those listed below represent some of the most common.
This problem develops during the extrusion process of the parison because the melt temperature is too cold. Also referred to as “doughnutting,” this happens for one of three reasons.
- The temperature of either the die or the mandrel is too cold at the time you start the blow molding machine. Once the temperature rises, the issue stops. For this, make sure you always give the machine ample time to warm up. Also, make sure the heater is working correctly.
- There is a misalignment of the die or mandrel. If the machine is warm but the parison still curls, make sure there is proper alignment of both the die and mandrel. If the edge of the mandrel recesses within the die, it causes the parison to make contact. With that, the parison becomes hung up on one side, causing it to curl.
- If the die has degraded resin or a foreign matter inside, it causes an uneven buildup. As a result, the parison becomes distorted during the extrusion process. The remedy is to keep the die clean.
As stated by a reputable blow molding manufacturer, if a pinch-off becomes worn, it results in flash. That makes it difficult to trim the plastic bottle or container.
- For this type of failure, you can make a tool from a single piece of machined aluminum to use on the mold. As a result, the blunt edges of the pinch-off sharpen, ensuring a clean and precise process.
This problem occurs for several reasons. As an example, resin with excessive swell, misaligned mold assembly, and excessive pre-blow air pressure are all culprits. To correct the problem, you would need to check all three of these to identify the cause of the excessive flash, followed by making the appropriate correction. For instance, if too much pre-blow air pressure is the problem, reduce it slightly. If that does not do anything, then adjust the nudge and bolts a small fraction on the mold assembly.
A Respected Blow Molding Manufacturer
The best way to avoid failure of a blow molding machine is to purchase machinery from a trusted and reliable source. At PET All Manufacturing, we offer our customers state-of-the-art machines. We also provide whatever support the customer needs. For your manufacturing process, please visit our website or call to learn about our full product line.