Injection Blow Molding Basics

Injection blow molding is a manufacturing process that combines the accuracy of injection molding with the minimal waste and rapid processing of blow molding. Injection blow molding can be used with plastics and is generally used to make hollow shapes such as bottles. The manufacturing process is more expensive than other blow molding techniques, so larger containers are generally fabricated using extrusion blow molding. The final products of injection blow molding have no seams, and can be glass clear.

Injection Blow Molding Process

The injection blow molding process has three phases: Injection of the material into the preform mold; blowing of the preform, or parison, into the product mold; and ejection of the product from the machine. A commonly used machine configuration is a three-stage blow molding machine, which rotates through 120 inches for each phase of the process. In the injection phase, molten plastic or glass is injected into the preform mold over a core pin, which forms the interior of the parison and finishes the interior of the neck. At this point, the neck of the container is fully formed. The parison is removed from the mold and inserted into the blow mold. The parison is inflated inside the blow mold by pressurized air. After a cooling period, the product is ejected from the machine, tested for leaks, and moved to another station for labeling or finishing.

Designing for the Injection Blow Molding Process

Designing products to be fabricated using injection blow molding includes selecting a thermoplastic resin for the product application, designing the mold geometry to take into account material shrinkage during cooling, calculating the right amount of material to be injected and choosing the right pressure to inflate the parison in the mold. Tolerances in the core rod and preform mold design are critical so that the core rod sits exactly in the center of the mold and the resulting parison has constant wall thickness prior to blowing.

Products Fabricated Using the Injection Blow Molding Process

Injection blow molding is used to create hollow products such as bottles, and is generally only used for small containers such as medicine bottles or single-serve beverage containers. The injection phase of the process can create a neck with very fine tolerances, with designs such as screw threads or threads for childproof caps. Unlike standard injection molding, undercuts can be incorporated into an injection blow molded design for some products, such as mascara bottles.

What Is the Blow Molding Process?

Blow molding is used to produce plastic bottles.

Blow molding is a method for making a variety of hollow plastic products. Molten plastic is extruded, in a tube shape, from a die, then a mold closes around it. The plastic is then inflated.

History

Blow molding first appeared late in the 1800s, but modern polyethylene bottle production did not commence until the early 1940s.

Types

The blow molding process can take four forms: reheat and blow molding, injection blow molding, stretch blow molding and extrusion blow molding. The machinery can vary significantly, though the major difference tends to be the point of plastic inflation.

Uses

The various processes are used to create a range of products, including bleach and milk bottles. Stretch blow molding is used in the production of PET (Polyethylene terephthalate) bottles, which are widely employed for carbonated beverages.

Plastics

The plastics used in the various blow molding processes can include HDPE (high density polyethylene), LDPE (low density polyethylene), PP (polypropylene), and PVC (polyvinyl chloride).

Disadvantages of Blow Molding

Blow molding is the process in which hollow, plastic containers are made. Air is blown into molds to form items such as thermoplastic bottles, tubing and milk jugs. While blow molding allows companies to manufacture high volumes of plastic containers, which are significantly cheaper than glass, there are a few disadvantages to the process. Some disadvantages include environmental hazards and a significant dependence on petroleum.

Environmental Disadvantages

Plastic products made by the process of blow molding aren't biodegradable, which presents an obvious environmental hazard, especially when empty containers find their way to landfills. When disposed of in landfills, plastic products are buried and remain in the earth forever. Their oil-based material then becomes part of the soil and runs the risk of threatening plant life, animals and groundwater.

Dependence on Petroleum

Aside from the gasoline industry, plastic manufacturers depend on millions of gallons of petroleum in their quest to produce blow-molded products. Because oil is the most important agent in thermoplastics and blow molding is becoming more streamlined and automated, the process plays an ongoing threat on a diminishing world oil supply.

Process and Material Limitations

Although blow molding has been automated and can produce mass quantities of products, the process is largely limited to hollow forms. These forms are delicate and contain various thicknesses which must be precise, which often results in wasted material in the process of arriving at containers with proper dimensions and specifications. In some cases, thermoplastic is stretched to save on material, which can lead to substandard containers.

      skype: lee.ivy66

      ivylee886@gmail.com

Free Technology Co., Ltd
http://www.freetech-mould.com

The Plastic Manufacturing Process

1.                            Plastic Injection Molding Process

Injection molding is one of the main methods by which parts are manufactured from plastic. The first step in the injection molding process is to feed plastic pellets into the hopper, which then feeds the pellets into the barrel. The barrel is heated and contains a reciprocating screw or a ram injector. A reciprocating screw is typically found in machines that produce smaller parts. The reciprocating screw crushes the pellets, making it easier for the plastic to be liquefied. Toward the front of the barrel, the reciprocating screw propels the liquefied plastic forward, thereby injecting the plastic through a nozzle and into the empty mold. Unlike the barrel, the mold is kept cool to harden the plastic into the correct shape. The mold plates are held closed by a large plate (referred to as a movable platen). The movable platen is attached to a hydraulic piston, which puts pressure on the mold. Clamping the mold shut prevents plastic from leaking out, which would create deformities in the finished pieces.

2.                            Plastic Extrusion Molding Process

Extrusion molding is another method of manufacturing plastic components. Extrusion molding is very similar to injection molding and is used to make pipes, tubes, straws, hoses and other hollow pieces. Plastic resin is fed into a barrel where it is liquefied. A rotating screw propels the liquefied plastic into a mold, which contains a tube-shaped orifice. The size and shape of the tube determines the size and shape of the plastic piece. The liquefied plastic then cools and is fed through an extruder, which flattens the plastic and forms the piece into its final shape.

Issues That Arise in the Plastic Manufacturing Process

A number of complications can arise during the plastic manufacturing process, including burned parts, deformities, surface imperfections and brittle parts. Parts become burned when the molds are not kept cool or if the melting temperature in the barrel is too high. Additionally, if the reciprocating screw becomes jammed or is not rotating fast enough, liquefied resin will remain in the barrel too long and become scorched. Surface imperfections and deformities occur when the surface temperature of the mold is uneven, if the molds are not clamped tightly enough or if the melting temperature is too high. Brittle pieces are formed when not enough liquefied resin is injected into the mold or if the plastic hardens before the mold can be filled. Regular testing and calibration of injection and extrusion molding machines is critical to ensure that the process runs smoothly.

http://www.freetech-mould.com/Successful%20Case.html

what's blow molding

Plastic blow molding technique is developing rapidly for plastic process . The thermoplastic resin obtained by extrusion or injection molding of plastic tubular parison hot ( heated or softened state ) , placed inside the mold cavity , then closed mold immediately, pour into air, blowing the plastic parison inflation and close to the inner wall of the mold cavity, cooled mold , that get all kinds of hollow plastic products.

 Technical Overview     Blow molding process during World War II began for the production of low-density polyethylene vial. In the late 1950s , with the development of high-density polyethylene birth and blow molding machines , blow molding technology has been widely used. Hollow container volume up to thousands of liters, and some have adopted computer-controlled production . For blow plastics are polyethylene, polyvinyl chloride, polypropylene, polyester, etc. , resulting into the empty containers are widely used in industrial packaging containers.

According to the production method of the parison , blow molding and extrusion blow molding can be divided into the injection blow molding, a newly developed multi-layer blow molding and stretch blow molding.

 

 Prospects    In recent years , with the development of a variety of functional beverages and wine packaging market , a variety of multi-layer co-injection - blow molding technology become a hot market .

Flexible step production technology

Injection stretch blow molding hollow articles having uniform thickness, good dimensional stability, light weight , high strength , etc., and therefore a very wide range of applications . As the injection stretch blow container craft production mostly PET, PP, PE, PVC and other materials as raw materials, and the use of these raw materials to produce bottles with light, portable, non-toxic , transparent, unbreakable , good barrier properties , etc., making it more and more as an alternative medicinal bottles were used in carbonated drinks, juice drinks , water , edible oil , alcohol , cosmetic products, pharmaceuticals and other industries packaging.

Injection stretch blow a two-stepprocessing method and one-step process . One step from raw material to complete the entire container molding process on a single device. Two-step process from the raw materials needed to complete the two devices to products molding process . Two-step method is mainly suitable for mass production , and flexibility, both equipped with a multiple injection blow molding machine can also be equipped with more than one injection blow molding machine . Of course, this should be based on production to match the main injection machine and blowing may be.