Rotary wheel blow molding systems are used for the high-output production of a wide variety of plastic extrusion blow molded articles. Containers may be produced from small, single serve bottles to large containers up to 20-30 liters in volume - but wheel machines are often sized for the volume and dimensional demands of a specific container, and are typically dedicated to a narrow range of bottle sizes once built. Multiple parison machines, with high numbers of molds are capable of producing over one million bottles per day in some configurations.
Rotary blow molding "wheels" are targeted to the high output production of containers. They are used to produce containers from one to seven layers. View stripe and In Mold Labeling (IML) options are available in some configurations. Rotary wheels, which may contain from six to thirty molds, feature continuously extruded parisons. Revolving sets of blow molds capture the parison or parisons as they pass over the extrusion head. The revolving sets of molds are located on clamp "stations".
Rotary wheels come in different variations, including both continuous motion and indexing wheels, and vertical or horizontal variations. [1] [2] Wheel machines are favored for their processing ease, due to having only single (or in some cases, two) parisons, and mechanical repeatability.
In some machinery configurations, the molds take on the shape of a "pie" sector. Thus, if two or more parisons are used, each blow molded "log" has a unique length, requiring special downstream handling and trimming requirements. In other machine configurations, the molds utilize "book style" opening mechanisms, allowing multiple parisons of equal length. However, machines of this style typically have lower clamp force, limiting the available applications.
The mold close and open actuation is typically carried out through a toggle mechanism linkage that is activated during the rotational process by stationary cams. This mechanical repeatability is considered an advantage by most processors.
The method of wheel rotation is typically conducted through an electric motor with a "pinion" gear or small gear to or in mesh with a rotating "bull" gear or large gear. All utilities for blowing containers and for mold cooling are carried through the main shaft or the axle from which the wheel rotates about. These utilities include compressed air and water. Sequencing functions necessary to inflate the parison, hold the container prior to discharge and discharge are completed by mechanical actuation to pneumatic valves – resulting in a high degree of repeatability.
Very tight weight and dimensional tolerances can be obtained on wheel equipment, as the parison is captured on both ends. It is pinched in the preceding mold on the leading end, and positioned by the stationary flowhead die on the other end. In shuttle machinery and reciprocating screw machinery multiple parisons are extruded and are free hanging. Because there is always some variation in the parison length on these machines, bottle weight and tolerance consistencies are not as tight as on rotary wheel machinery.
Other advantages of wheel equipment include:
Disadvantages:
The growth of wheel machinery in the United States was spurred by the conversion of motor oil containers from paperboard cans to plastic bottles, and the conversion of laundry detergent from powder to liquid form. Additional high volume applications have included single-serve juices and drinkable yogurt, condiments, and household cleaning supplies.
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A rotary encoder, also called a shaft encoder, is an electro-mechanical device that converts the angular position or motion of a shaft or axle to analog or digital output signals.
Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex cross-sections; and to work materials that are brittle, because the material encounters only compressive and shear stresses. It also creates excellent surface finish and gives considerable freedom of form in the design process.
Thermoforming is a manufacturing process where a plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mold, and trimmed to create a usable product. The sheet, or "film" when referring to thinner gauges and certain material types, is heated in an oven to a high-enough temperature that permits it to be stretched into or onto a mold and cooled to a finished shape. Its simplified version is vacuum forming.
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Punching is a forming process that uses a punch press to force a tool, called a punch, through the workpiece to create a hole via shearing. Punching is applicable to a wide variety of materials that come in sheet form, including sheet metal, paper, vulcanized fibre and some forms of plastic sheet. The punch often passes through the work into a die. A scrap slug from the hole is deposited into the die in the process. Depending on the material being punched this slug may be recycled and reused or discarded.
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In-mould labelling is the use of paper or plastic labels during the manufacturing of containers by blow molding, injection molding, or thermoforming processes. The label serves as the integral part of the final product, which is then delivered as pre-decorated item. Combining the decoration process with the moulding process cuts the total cost, but can increase the manufacturing time. The technology was first developed by Owens-Illinois in cooperation with Procter & Gamble to supply pre-labelled bottles that could be filled on the product filling line. This was first applied to Head & Shoulders shampoo bottles.
Plastics extrusion is a high-volume manufacturing process in which raw plastic is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weatherstripping, fencing, deck railings, window frames, plastic films and sheeting, thermoplastic coatings, and wire insulation.
Injection molding of liquid silicone rubber (LSR) is a process to produce pliable, durable parts in high volume.
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A rotary union is a union that allows for rotation of the united parts. It is thus a device that provides a seal between a stationary supply passage and a rotating part to permit the flow of a fluid into and/or out of the rotating part. Fluids typically used with rotary joints and rotating unions include various heat transfer media and fluid power media such as steam, water, thermal oil, hydraulic fluid, and coolants. A rotary union is sometimes referred to as a rotating union, rotary valve, swivel union,rotorseal, rotary couplings, rotary joint, rotating joints, hydraulic coupling, pneumatic rotary union, through bore rotary union, air rotary union, electrical rotary union, or vacuum rotary union
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Covema srl was a historic Italian company specializing in the design of plastic processing machinery, based in Milan, via Fontana 1. Founded in 1953 by the Terragni brothers, it also included the companies Corima spa, GBF spa, GBF iberica, RIAP srl, FIRS spa, Covepla Spain, Italproducts srl, Omam spa, TPA srl, AGRIPAK srl, Floraplant srl, Interfinance SA, Technical Die spa, Covema SAE. The technology that Covema has developed since the 1950s is merged into Agripak srl based in Milano and managed by the sons of Marco Terragni: Fabio Terragni (president), Patrizia Terragni and Massimo Terragni.
