Plastic Blow Molding
Plastic blow molding is a manufacturing process used to create a vast array of hollow plastic parts and products.
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Advantages of Plastic Blow Molding
No matter which technique a manufacturer uses, plastic blow molding is a highly advantageous process for a number of reasons. First, it offers high-volume productivity at fairly low costs. Second, it yields high turnaround times. Typically, the process can be completed in a matter of seconds, and the resulting products require minimal secondary processing. Also, the use of plastic itself, as opposed other materials, affords manufacturers an incredible amount of versatility; plastic is durable and has a uniform, consistent structure down to a molecular level, yet it is very malleable. To find out more about plastic blow molding, contact a knowledgeable manufacturer today.
Design of Plastic Blow Molding
Blow molding gets its name from its use of a form of plastic called a parison. The parison is actually plastic that has been melted down and preformed into a tube-like shape with a hole at one end. Through this hole, after it is clamped to a mold, compressed air (conveyed by a blow pin) is blown in to expand it. When expanding, the parison behaves like a balloon, expanding uniformly with the assistance of a constant and controlled air flow. This behavior leads to walls and structures that, once set, are thin, strong and durable. Blow-molded pieces additionally tend to be smooth, airtight; they do not require joining. Examples of items created by blow molders include toys, beverage bottles, hose, buckets, storage and transportation cases, garbage and recycling cans and countless other luxury and everyday use products of industries across the board.
Types of Plastic Blow Molding
The plastic blow molding is completed when the created cavity is cooled and removed from mold as a hardened plastic product. This point may be reached using three different processes: extrusion blow molding (EBM), injection blow molding (IBM) and injection stretch blow molding.
- Extrusion Blow Molding
- The process described in the paragraph above details one of these, extrusion blow molding. As perhaps the most common style of plastic blow molding, its description is often used interchangeably with it. It has a distinguishing feature, however, which is that it uses a metal mold. EBM is divided into two categories: continuous and intermittent. Some of the products created through either type of EBM include watering cans, plastic drums, shampoo bottles and milk bottles. Also, a major advantage of this process is its ability to create handleware.
- Injection Blow Molding
- Next, injection blow molding is a process that incorporates elements of standard injection molding in order to produce parts and products in large quantities. IBM involves three steps: injection, blowing and ejection. The process begins when a molten polymer is fed into a hot runner manifold and injected via nozzles into a heated cavity and onto a core pin. The polymer surrounding the pin takes on the shape of the cavity, forming an exterior, while the core pin ensures that it remains hollow. This pin then rotates its way to a blow molding station, where the mold is clamped around a core rod, inflated inside a preform and cooled. Once hardened, the finished product is moved into the ejection position and stripped off the core rod. IBM is the least frequently used plastic blow molding process. Generally, it is only used to create small capacity bottles and jars.
- Injection Stretch Blow Molding
- Finally, injection stretch blow molding, or stretch blow molding, is a process much like IBM. The main difference between the two is that stretch molding involves the use of bottle-shaped preforms, which are later reheated then stretched into their intended shape and size using pressurized air and core rods. Stretch blow molding is known for producing very high volumes of oval, rectangular or cylindrical bottles.