Design and Manufacture of Pet and Polyethylene Molds
Blow molding is a special manufacturing process that creates hollow plastic parts that can be joined together. These parts are also used to make glass bottles or other hollow shapes.
Plastic preforms are used to make PET bottles, but to make metal cans, metal sheets are made by stretching and cutting with press and hammer machines.
In the design of PET bottles, it is necessary to be very careful about the shape of the preform, the size of the opening and its weight, the air exit holes, the mechanism of the mold and finish, and the exit angles of the part.
For molding with the help of wind, the desired device should be selected according to the type of material and technique, usually the granules are injected into the mold and are stuck to the walls by the wind and the material is produced in a hollow form and removed from the mold.
Blow molds are mainly divided into two categories: aluminum molds (usually for the use of PET and polycarbonate or PC bottles) and steel molds (usually for the use of LDPE and HDPE polyethylene bottles).
The price of blow molds is calculated and announced according to the material used, the volume of the container, the complexity of the design, and the number of cavits.
Many devices with high diversity are used in the production of blow molds, the most widely used of which are the pet devices, which include ovens and blowers, in which the preform is placed, and after preheating, it is inflated and takes its final shape. Also, polyethylene blow devices that are continuously lowered in the form of a gut and take the final shape of the container with the wind.
The answer to the question of what is PET requires knowing its abbreviation, PET with the abbreviation PET is a type of plastic material that is used more in the food and hygiene industries. PET preform is used in aluminum air molds.
Work Samples of Manufacturing pet and polyethylene molds
Types of molding methods in the design and manufacture of pet and polyethylene molds
Extrusion mold
In the extrusion method, plastic is melted and extruded in a hollow tube. Then this parison is placed in a cool metal mold. Air is then blown into the parison, inflating it into a hollow bottle, container, or part thereof. After proper cooling of the plastic, the mold is opened and the final product is removed.
The technology of making pet mold
Technologies such as compression and injection at the same time, which are used for Pet molds and other plastics, allow the packaging of food and other products. But in general, one should be careful and control the process from moment to moment so that when the ingredients inside the mold are melted, the walls of the container are not voided or destroyed.
Injection mold
- In order to produce a product using an injection-type polyethylene inflatable mold, polymer materials are injected into the mold using different methods At this stage a preform in the form of a tube will be created in the middle of the mold so that it is possible to blow air in this part.
The most obvious advantage of producing products using injection molds is the reduction of waste. The products that are produced using these molds will have the lowest rate of pleats and extra parts, which makes the need for cutting after production to be greatly reduced or even eliminated.
Advantages
- Creates an injection mold opening for accuracy
Disadvantages
- Only suitable for small capacity bottles as it is difficult to control the center of the base during blowing.
- Because the material is not stretched in two axes, no strength is increased in the barrier.
- Categories cannot be combined.
Injection stretch blow molding
- One of the types of air injection molding is stretch molding. For this reason, it is included in the category of air molding, which was originally called injection molding or extrusion molding. Its production process includes conditioning or heating a preform to a certain temperature and placing it in a cold mold.
When the mold is closed, it is blown into the mold using a special lever and needle for air pressure. Then it stretches the piriform very quickly in both longitudinal and diagonal directions.
In this type of molding, four plastics are usually used. These four plastics include polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET) and polyacrylonitrile (PAN), which are most commonly used for stretch blow molding, soft drink bottles made of PET, which can be used in two It can be used in transparent or colored mode.
Advantages
- It causes a very high volume in production.
- There is little limitation in bottle design.
- Preforms can be sold to a third party as a complete product.
- Suitable for cylindrical, rectangular or oval bottles.
Disadvantages
- High capital cost.
- The floor space required is large, although compact systems are becoming available.