BLOW & ROTATIONAL MOLDING: Meaning, Advantages & Disadvantages

Blow & Rotational molding process

Hello Readers, welcome to your own website to understand each and every topic related to the manufacturing process where we transform complex content into simpler ones. In this article, we are focused to cover blow and rotational molding, advantages, disadvantages and applications.

BLOW MOLDING:

Blow molding is a modified extrusion and injection molding cycle.

In extrusion blow molding, a cylinder or preform (typically arranged with the goal that it is vertical) is first expelled.

Extrusion blow molding process
Extrusion blow molding process for making plastic beverage bottles

It is then braced into a mold with cavity a lot bigger than the cylinder measurement and blown outward to fill the mold with cavity.

Depending on the material, the blow proportion may be as high as 7:1. Blowing casually finish with a hot air blast at a pressure factor going from 350 to 700 kPa (50 to 100 psi).

Drums with a volume as large as 2000 liters (530 gallons) can be made by this process.

Typical die materials are steel, aluminum, and beryllium copper.

In certain tasks, the extrusion is continuous and the molds move with the
tubing.

The molds stop around the tubing, sealing off one end, breaking the long
tube into singular areas, and moving side as air is injected into the tubular
piece.

The part is then cooled and ejected from the mold.

Corrugated plastic pipe and tubing are made by constant blow molding in which the pipe or tubing is expelled horizontally and blown into moving molds.

In injection blow molding, a short tubular piece (parison) is injection molded into cool dies (Parisons may be made and stored for later use).

Injection blow molding process
Injection blow molding process

The dies then open, and the parison is moved to a blow molding die by an indexing mechanism.

Hot air is infused into the parison, extending it to the walls of the mold cavity.

Most of products made are plastic drink bottles (typically made of polyethylene or polyetheretherketone, PEEK) and little, empty containers.

Injection blow molding process
Injection blow molding for making plastic bottles

A connected cycle is stretch blow molding, in which the parison is extended and elongated at same time, exposing the polymer to biaxial stretching and subsequently improving its properties.

Multilayer blow molding includes the utilization of coextruded tubes or parisons and in this way allows the production of a multilayer structure.

A average illustration of such a product is plastic packaging for food and drinks, having such characteristics as smell and permeation obstruction, taste and aroma security, scuff obstruction, the capacity of being printed, and the capacity to be load with hot fluids.

Different uses of this process are for containers in the cosmetics and the pharmaceutical ventures.

Blow molding is utilized mostly to make bottles and other lightweight, hollow plastic parts.

Two techniques are utilized: injection blow molding and extrusion blow molding.

Injection blow molding is utilized primarily for little containers.

The parison (molten-plastic pipe) or tube is created with the help of injection of plasticized material around a hollow mandrel.

While the material is yet liquid and still on the mandrel, it is moved into the blowing mold where air is utilized to expand it.

Precise threads may be formed at the neck.

Air enters through the mandrel and blow up the cylinder until the plastic contacts the cold wall, where it solidifies.

ADVANTAGES OF BLOW WELDING:

It can be able to produce variable product.

It is of low cost.

It give permit to multiple production methods.

It helps to promot productivity.

It offers benefits in automation.

DISADVANTAGES OF BLOW MOLDING:

Mostly depends on petroleum.

Aslo it’s most impact is on environment.

It require many methods.

It comes with limited uses.

APPLICATIONS OF BLOW MOLDING:

Injection blow moulding is utilizes for the production of hollow objects in big quantities.

The important applications are bottles, jars and other containers.

The Injection blow moulding process produces bottles of superior visual and dimensional quality rather than extrusion blow moulding

ROTATIONAL MOLDING:

Most thermoplastics and some thermosets can be shaped into huge, empty parts by rotational molding.

Rotational molding process
Rotational molding process

In this long process, a thin-walled metal mold is form in two pieces (split female mold) and is intended to be rotated about two perpendicular axes.

For each part cycle, a pre measured amount of powdered plastic material is set inside the warm mold.

The powder is received from a polymerization process that precipitates a powder from a fluid.

Then the mold is heated (generally in a large oven) and is moving continuously about the two principal axes.

This activity tumbles the powder against the mold, where the heat fuses the powder without melting it.

The rotational molding machine are exceptionally robotizes, with parts moved by an indexing mechanism same to that.

A enormous assortment of parts are made by rotational molding, such as storage tanks of various sizes, trash cans, boat hulls, buckets, housings, large hollow toys, carrying cases, and footballs.

Different metallic or plastic addition or components also may be molded necessarily into the parts made by this process.

In addition to powders, fluid polymers (plastisols) might be utilized in rotational molding PVC plastisols being the most widely recognize material.

In this methods (called slush molding or slush casting), the mold is heated up and moving with same time.

Because of the tumbling action, the polymer is forced against the inside walls of the mold.

The part is cooled while it is already moving and removed by opening the mold.

PROCESS CAPABILITIES:

Rotational molding can create parts with perplexing, empty shapes with wall thicknesses as small as rotational molding (rotomolding or rotocasting) process.

By using rotational molding process the trash cans, buckets, and plastic footballs are made.

ADVANTAGES OF ROTATIONAL MOLDING:

It is an low cost tooling process.

It produces consistent wall thickness.

Double wall construction.

It has high stability.

DISADVANTAGES OF ROTATIONAL MOLDING:

It require a high cycle time.

In this there are limited material options.

There is high cost of raw material.

In this there is low repeatability.

High labour costs.

APPLICATIONS OF ROTATIONAL MOLDING:

Tanks produced using rotational molding (which can be used for storing water, chemicals, sewage, fuel, and other liquids) can hold up to 50,000 liters.

Some types of plastic tanks produced with this process include fuel and oil tanks, septic tanks, water treatment tanks, and shipping tanks.

3 thoughts on “BLOW & ROTATIONAL MOLDING: Meaning, Advantages & Disadvantages”

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