Rotary wheel blow molding systems
Encyclopedia
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.
s. 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. 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:
containers from paperboard
cans to plastic bottle
s, and the conversion of laundry detergent
from powder to liquid form. Additional high volume applications have included single-serve juice
s and drinkable yogurt
, condiment
s, and household cleaning supplies.
Blow molding
Blow molding is a manufacturing process by which hollow plastic parts are formed. In general, there are three main types of blow molding: extrusion blow molding, injection blow molding, and stretch blow molding. The blow molding process begins with melting down the plastic and forming it into a...
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.
Description
Rotary blow molding “wheels” are targeted to the high output production of containerContainer
Container may refer to:* Items used to contain, store, and transport products, such as:** Carton** Bottle** Can , several meanings* Shipping containers include** Crate** Wooden box...
s. 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. Wheel machines are favored for their processing ease, due to having only single (or in some cases, two) parisons, and mechanical repeatability.
The mold close and open actuation is typically carried out through a toggle mechanism
Linkage (mechanical)
A mechanical linkage is an assembly of bodies connected together to manage forces and movement. The movement of a body, or link, is studied using geometry so the link is considered to be rigid. The connections between links are modeled as providing ideal movement, pure rotation or sliding for...
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.
Advantages & disadvantages
Other advantages of wheel equipment include:
- Continuous extrusion
- Multi-layer coextrusion, with one to seven layers of plastic in the finished part
- In some applications, In Mold Labeling (IML) can be integrated with little or no cycle time penalty
- Parison programming capability, for optimization of wall thickness
- Reduced cycle time on light weight containers, compared to shuttle machinery. Conversely, wheel equipment may suffer cycle time penalties on thick containers
- Easily implemented view stripe capability
- Ability to achieve very high outputs from a single machine - lowest "cost per bottle" when compared to other blow molding equipment
- Higher production efficiencies than most other extrusion blow molding equipment types
Disadvantages:
- Inability to produce bottles with calibrated neck finishes
- Downstream trimming required
- Machines typically dedicated to a narrow range of sizes. Product change can be difficult, especially when downstream trimming changeovers are required.
- High initial capital investment
Applications
The growth of wheel machinery in the United States was spurred by the conversion of motor oilMotor oil
Motor oil or engine oil is an oil used for lubrication of various internal combustion engines. The main function is to lubricate moving parts; it also cleans, inhibits corrosion, improves sealing, and cools the engine by carrying heat away from moving parts.Motor oils are derived from...
containers from paperboard
Paperboard
Paperboard is a thick paper based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker than paper. According to ISO standards, paperboard is a paper with a basis weight above 224 g/m2, but there are exceptions. Paperboard can be single...
cans to plastic bottle
Bottle
A bottle is a rigid container with a neck that is narrower than the body and a "mouth". By contrast, a jar has a relatively large mouth or opening. Bottles are often made of glass, clay, plastic, aluminum or other impervious materials, and typically used to store liquids such as water, milk, soft...
s, and the conversion of laundry detergent
Laundry detergent
Laundry detergent, or washing powder, is a substance that is a type of detergent that is added for cleaning laundry. In common usage, "detergent" refers to mixtures of chemical compounds including alkylbenzenesulfonates, which are similar to soap but are less affected by "hard water." In most...
from powder to liquid form. Additional high volume applications have included single-serve juice
Juice
Juice is the liquid that is naturally contained in fruit or vegetable tissue.Juice is prepared by mechanically squeezing or macerating fruit or vegetable flesh without the application of heat or solvents. For example, orange juice is the liquid extract of the fruit of the orange tree...
s and drinkable yogurt
Yoghurt
Yoghurt, yogurt or yogourt is a dairy product produced by bacterial fermentation of milk. The bacteria used to make yoghurt are known as "yoghurt cultures"...
, condiment
Condiment
A condiment is an edible substance, such as sauce or seasoning, added to food to impart a particular flavor, enhance its flavor, or in some cultures, to complement the dish. Many condiments are available packaged in single-serving sachets , like mustard or ketchup, particularly when supplied with...
s, and household cleaning supplies.
Books, general references
- Soroka, W, "Fundamentals of Packaging Technology", IoPP, 2002, ISBN 1-930268-25-4
- Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6