Blow Molding Machines
Blow molding machines produce hollow-bodied plastic products used by millions of people every day. These include bottles for beverages, cleaning products, and food. They look like test tubes and are inflated by compressed air to create the final product shape.
The most common type of blow molding is extrusion blow molding (EBM). This process uses an extruder barrel and screw to melt and feed plastic material into a die.
Extrusion
Extrusion blow molding is one of the most popular types of plastic blow molding. It uses the same basic steps as injection blow molding, but creates a hollow plastic product. It is used to produce containers for food, drinks, and household products, like bottles and jars. This process starts with raw plastic pellets that are conveyed into the machine’s extruder through a silo or hopper. The pellets are heated using frictional heat and sheer force to transform them into molten plastic. The plastic is then shaped into a hollow tube of a desired shape called a parison.
The parison is then placed into a product mold and pressurized air is forced into the cylinder to form the final product shape. This process can be blow molding machine used to make a variety of shapes, including those with a handle structure. The extra plastic on the ends of the parison is trimmed away for recycling.
The cooled product then gets ejected from the mold after a set time, and the parison is reheated for the next cycle. The trimmed excess plastic is known as flash and can be recycled back into the raw material stream for the extruder.
Clamping
A key function of a blow molding machine is clamping. The clamp must be able to hold the mold halves together with a high force and accuracy. The force must be enough to keep the molded plastic in place and withstand the pressure introduced by inflation of the parison. It must also be able to trim off tails and flash from the formed plastic.
The clamp is mounted on a frame for limited vertical movement at the work stations and during movement between the work station. The clamp carries a pair of opposed platens for carrying the mold sections. The clamp body has a pair of levers pivotally coupled with the platens and connected to each other by a pull bar. The pivotal couplings on the levers are spaced so that displacement of one of the platens imparts equal and opposite displacement of the other platen.
The actuating assembly 100 may be a hydraulic, pneumatic or linear actuator. It drives the shift member 62′ and the two tension rods 38′ to move the mold halves 32′ and 34′ between open and closed positions.
Inflating
Blow molding is a versatile manufacturing process that produces a wide range of hollow plastic products. It uses a variety of materials, including polyethylene, acrylonitrile butadiene styrene (ABS), and styrene acrylonitrile (SAN). These materials are commonly used in beverage bottles, food packaging, and other household and industrial products.
The first step in the blow molding process is to melt the plastic resin into a molten state. Then, the machine shapes the heated plastic into a tube known as a parison. The parison is then clamped into a mold, which gives the final product its shape. Air is blown into the parison to “blow” it into the mold, like blowing up a balloon.
The mold must be precise to ensure that the plastic conforms to its intended shape. Once the plastic has taken on the mold’s shape, it must be cooled quickly to avoid deformation and loss of strength. The cooling system on a blow molding machine is responsible for this process, which can take as little as 1.5 seconds. In addition, the machine should be able to open and index the mold in less than 2.7 seconds.
Cooling
Blow molding is an ideal option for producing hollow-bodied workpieces. This process uses compressed air to blow molten plastic into a mold and create the desired shape. Then, the plastic cools and the product is ejected from the mold without damaging it. Depending on the material and size of the product, cooling takes seconds or minutes.
The first plastic blow molding processes used natural rubber, cellulose acetate, or a preform made ahead of time, known as injection molding. In the 1930s, inventors developed a mass manufacturing technique that replaced glass with plastic. blow molding machine factory Then, in 1939, low-density polyethylene was introduced, paving the way for a major breakthrough in the industry.
Wittmann Battenfeld’s IACS system promises to increase production up to 50% over conventional water-based cooling. This method exchanges cooled dry air in the internal part of the product during the cooling cycle, increasing product quality and shortening the production period. It also reduces the stress on the product surface and ensures homogeneous cooling. It can even be customized for custom products to guide airflow to thicker walls or areas of the mold that are less easily cooled.
Ejection
Millions of plastic bottles are produced using the extrusion blow molding process each day. These containers carry soda, water, cleaning products, and many other everyday items. The process uses low-pressure air to blow a tube of plastic known as a parison into a mold. It is then inflated until it reaches the desired shape of the final product. Once it is cooled, it can be removed from the machine.
The ejection phase on a blow molding machine occurs when the hot, inflated plastic is released from its mold. This process requires a properly functioning ejection system that can move the mold open and close quickly without damaging the plastic or the ejection pins.
Blow molded plastic products are used across all areas of industry and life. From shampoo bottles to tool boxes and from car ducting to manufacturing tubs, blow molding materials are essential in our daily lives.
