High-Density PolyEthyene (HDPE) Low-Density PolyEthyene (LDPE) PolyPropelen (PP) PolyVinyl Chloride (PVC) PolyStyrene (PS) PolyEthylene Terephthalate (PET)
Injection Molding Injection Blow Molding Extrusiion Blow Molding Injection Stretch Blow Molding
There are two primary types of plastics: thermosets and thermoplastics. The main difference between these two types of plastics is that thermosets permanently cure. This means that once the plastic is melted into a shape, it cannot be melted back down to molten plastic. Once the plastic takes a shape, it will retain that shape. If the plastic is melted, it simply burns. This is different from thermoplastics, which can be cured into a shape, then melted back down to molten plastic and reformed through further curing. ( - Thomas Publishing - )
The molding process is a technique through which a material, commonly plastic, but also metal, rubber, or powder mixtures, is shaped on the outline of a die or mold, often via a plastic molding machine. There are many different techniques for molding materials, just as there are many different applications for each molding process. ( - Thomas Publishing - )
Injection molding is a manufacturing process for producing parts by injecting molten material into a mold. Injection moulding can be performed with a host of materials mainly including metals (for which the process is called die-casting), glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed (using a helical screw), and injected into a mould cavity, where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineer, moulds are made by a mould-maker (or toolmaker) from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection moulding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. Advances in 3D printing technology, using photopolymers that do not melt during the injection moulding of some lower-temperature thermoplastics, can be used for some simple injection moulds. (- Wikipedia - )
In extrusion blow molding, plastic is melted and extruded into a hollow tube (a parison). This parison is then captured by closing it into a cooled metal mold. Air is then blown into the parison, inflating it into the shape of the hollow bottle, container, or part. After the plastic has cooled sufficiently, the mold is opened and the part is ejected. (- Wikipedia - )
The process of injection blow molding (IBM) is used for the production of hollow glass and plastic objects in large quantities. In the IBM process, the polymer is injection molded onto a core pin; then the core pin is rotated to a blow molding station to be inflated and cooled. This is the least-used of the three blow molding processes, and is typically used to make small medical and single serve bottles. The process is divided into three steps: injection, blowing and ejection. (- Wikipedia - )
Single-Stage ISBM In the single-stage process, both preform manufacture and bottle blowing is performed in the same machine. The older 4-station method of injection, reheat, stretch blow and ejection is more costly than the 3-station machine which eliminates the reheat stage and uses latent heat in the preform, thus saving costs of energy to reheat and 25% reduction in tooling. The process explained: Imagine the molecules are small round balls, when together they have large air gaps and small surface contact, by first stretching the molecules vertically then blowing to stretch horizontally the biaxial stretching makes the molecules a cross shape. These "crosses" fit together leaving little space as more surface area is contacted thus making the material less porous and increasing barrier strength against permeation. This process also increases the strength to be ideal for filling with carbonated drinks. Two-stage ISBM In the two-stage injection stretch blow molding process, the plastic is first molded into a "preform" using the injection molding process. These preforms are produced with the necks of the bottles, including threads (the "finish") on one end. These preforms are packaged, and fed later (after cooling) into a reheat stretch blow molding machine. In the ISBM process, the preforms are heated (typically using infrared heaters) above their glass transition temperature, then blown using high-pressure air into bottles using metal blow molds. The preform is always stretched with a core rod as part of the process. (- Wikipedia - )
