Blow molding mold, also known as hollow blow molding, is a rapidly developing plastic processing method. Blow molding technology was first used to produce low-density polyethylene bottles during World War II. In the late 1950s, with the birth of high-density polyethylene and the development of blow molding machines, blow molding technology was widely used. The temperature of the mold is usually controlled by adjusting the temperature of the heat transfer medium and adding insulation boards and heating rods. The heat transfer medium is usually water, oil, etc., and its channel is often referred to as a cooling water channel. What are the ways to control the temperature of the blow molding mold components and improve the quality of the products?
Lower the mold temperature
Generally, machine water (about 20°C) is used to pass through the front mold and frozen water (about 4°C) is used to pass through the rear mold. When the channel of the heat transfer medium, i.e., the cooling water channel, cannot pass through certain parts, materials with high heat transfer efficiency, such as beryllium copper, should be used to transfer heat to the heat transfer medium, or "heat pipes" should be used for local cooling.
Raise the mold temperature
Generally, hot water or hot oil (heated by a hot water machine) is used to pass through the cooling water channel. When the temperature of the blow molding mold parts is required to be high, to prevent heat conduction from causing heat loss, insulation boards should be added to the mold surface panel.
The importance of blow molding equipment in industrial production is self-evident. A large number of plastic products are manufactured by blow molding. The more common blow molding methods include extrusion molding, and problems with poor product quality inevitably occur during the production process.
Blow expansion pressure
Blow expansion pressure can make the semi-molten tube blank blow and adhere to the mold cavity wall to form the required shape. It can also cool the blow molded product. Generally, overlarge or too small blow expansion pressures for large-volume products are not conducive to production, and choosing a suitable pressure makes the external pattern of the product clearer.
Blow expansion rate
In order to obtain blow molded products quickly and shorten the blowing time, a large amount of air should be injected in a short time to ensure that the mold cavity of the blow molding mold expands uniformly and rapidly and to shorten the cooling time in the mold cavity.
Blow molding mold temperature
Mold temperature has a great influence on the appearance of blow molded products. Generally, the mold temperature should be cooled as evenly as possible, and the mold temperature is related to the type of plastic, the thickness, and size of the product. When the mold temperature of different types of blow molding molds is too high, the cooling time will be prolonged, the production cycle will be increased, and the production efficiency will be reduced. If the cooling is not enough, it will also cause the product to deform, increase the shrinkage rate, and decrease the surface gloss. Generally, for plastics with higher molecular chain rigidity, the mold temperature should be higher; for plastics with larger molecular chain flexibility, the mold temperature should be lower.