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.

Parison Curl

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.