Blow Molding Machines
Blow molding is the process of producing hollow-bodied plastic products. It accounts for a substantial share of industrial manufacturing.
Plastic resin is fed into an extruder that creates a tube shape of melted plastic called parison. A parison is then captured by a split mold and pressurized air is blown into it, which inflates the preform into a desired product shape.
Process
Blow molding is a manufacturing process that creates hollow plastic objects such as bottles and containers. It’s based on the principle of glassblowing. Plastic is heated to form a parison, which is a test tube-like piece with a hole in the neck area that allows compressed air to pass through. The parison is clamped into a two-part mold and air is blown to force it into the shape of the mold. The molded product is then allowed to cool and ejected from the mold. The extrusion blow molding (EBM) process is the most commonly used.
The first step in the blow molding process is feeding or charging the plastic resin. It can be done using an injection pump and a silo or a vacuum conveying system. Plastic pellets are drawn from large bags or containers and placed in a hopper. Then a compressor pumps in air to pneumatically convey the plastic pellets into the plastifier or extruder hopper.
Injection stretch blow molding (ISB) is the least used of the three blow molding processes. It involves injecting a polymer onto a core pin that rotates at a blow molding station where it is inflated and cooled. This allows the plastic to conform to a mold and it’s a good choice for producing HDPE, LDPE and PP bottles with tight neck tolerances. However, it’s less flexible in wall thickness compared to injection molding and requires more precision which leads to waste.
Materials
The blow molding process can use a variety of materials, depending on the application. It is commonly used to manufacture plastic bottles and jars for food, beverage, personal care, and cosmetics. It can also be used to make drums and tubs for household products and manufacturing equipment. It is widely employed in the automotive industry for items like vehicle fluid storing bins, cooling systems, and fuel tanks. It is also commonly used in the medical industry for spray water bottles and storage containers for medications and sanitizers.
Blow molds can be made from various materials, including acrylonitrile butadiene styrene (ABS) and polyvinyl chloride (PVC). ABS is a hard plastic that resists impact well. It can be colored to create distinct shapes and has good chemical resistance. Its surface is usually treated with a coating to electric fan supplier protect it from stains and scuffing. It can be recycled as code 7.
PVC is a clear plastic that is soft and resistant to oils. It can be extruded in either rigid or soft forms and has excellent barrier properties to gases. It has low permeability to water and is not reactive to acids. It has gained notoriety in recent years for containing cadmium and lead as stabilizers, and releasing hydrochloric acid during processing and electric fan company vinyl chloride monomers after molding. It can be recycled as code 7. It is often coated with ionomers to provide added performance properties.
Equipment
The process of blow molding a plastic object involves forcing air into a heated hollow plastic tube called a parison. This inflated plastic conforms to the mold and cools. Once cooled, the mold opens and ejects the molded plastic workpiece. Blow molding is used to produce many of the bottles and containers we use on a daily basis for soda, water, cleaning products, etc.
There are several different types of blow molding machines used to manufacture the blown plastic objects. For example, Graham Engineering Corporation offers Rotary Wheel Blow Molding Systems known for their high production capabilities and energy efficiency. Wilmington Machinery, meanwhile, provides Extrusion Blow Molding Machines that feature a compact footprint and precise parison control.
Some blow molding machines, like continuous or intermittent extrusion, utilize an accumulator that gathers melted plastic resin from the extruder until enough has accumulated to push it into the mold cavity. Other types of machines, like the intermittent-discharge accumulator type, utilize a linear piston to push melted plastic through a die to create the shaped parison.
The earliest blow molding techniques were similar to glassblowing and involved a craftsman heating and inflating glass to shape it. Two inventors, Enoch Ferngren and William Kopitke developed a blow molding machine in 1938 which made mass manufacturing possible and allowed the number of plastic bottles to increase.
Safety
Blow molding machines are used to make a variety of plastic products, including bottles and containers. A crucial step in this process is the mold trial, which must be accurate and complete in order to produce high-quality, uniform plastic products that meet specific quality standards. In order to ensure successful mold trials, manufacturers should take several precautions during the blow molding process.
Identifying the right raw materials is vital, and it is also important to check that the blow molding machine settings are configured correctly for the type of product being produced. In addition, the mold must be properly prepared and kept clean.
Another essential safety measure is to reduce noise levels around the blow molding machines by isolating them or enclosing them within noise barriers. In addition, the area around the machines should be free of trip and slip hazards. It is also important to lock out power supplies before performing maintenance, cleaning or repairs on them.
A final safety measure is to make sure that all warning plates on a blow molding machine are intact and not missing. If they are, these should be replaced or complemented accordingly. Additionally, all personnel should always wear personal protective equipment when working with blow molding machinery. Finally, employees should never disconnect or by-pass any of the machine’s safety devices.
