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Making Plastic Mold-Plastic Injection Moulding

Ever wondered how plastic is moulded into the exceptionally useful things that we employ in our daily life? Is it as simple as melting plastic and lathering the sides of a mould with it and cooling it, much like chocolate? The answer, actually, is no. Moulding plastic is a little more complex than that. Plastic is made using a process often called plastic injection moulding.

What is this type of moulding

Plastic injection moulding is the method of manufacturing parts made of thermoplastic and thermosetting plastic by melting and forcing into moulds where they cool to form the desired object.
How does plastic injection moulding work?

The process of plastic injection moulding usually begins with an industrial designer or engineer who designs a product. This is followed up by the work of a toolmaker or mould maker who makes the mould to fit the design created. These moulds are metallic and usually made using either steel or aluminum. Using machines, they are made to acquire the exact shape desired by the design. Once this is done, the process of actually making the plastic follows. This involves thermoplastic and thermosetting plastic being fed into a heated barrel and mixed. This melted material is then forced into the cavity of a mould and there it cools and hardens to form the desired part.

Some characteristics of the process:

1. I uses melted and mixed thermoplastic or thermoset plastic as the base
2. It uses a plunger which acts like a screw or a ram to force the melted material in the mould
3. It makes a shape that is open-ended and has taken the shape of the cavity of the mould
4. It shows a parting line and gate marks on the finished products and the ejector pin marks can also usually be made out

Some history

Alexander Parkes invented plastic in 1851 in Britain. This was worked on and bettered by John Hyatt, an American inventor in 1868. He also patented, in 1872, the first injection moulding machine. In the 1940s, the need for mass production of plastic products increased and saw the invention of the first screw injection machine by inventor James Hendry of America. This increased not only the speed of production but also the amount of precise control that could be exercised on the finish of the product.

Since then, this type of moulding has been used widely in the production of everything right from milk cartons to entire car panels and automotive parts. Since it is not a very costly material, it is best suited for mass produced goods.

Advantages of this type of moulding:

1. The rate of production are very high and therefore mass production is much benefitted
2. Since tolerance levels are high, they can be repeated
3. The labour cost is very low
4. The losses in scrap are very minimal
5. The products require very minimal finishing
6. A wide range of materials can be used

Disadvantages using this type of moulding:

1. Although labor expense and scrap loses are minimal, the cost of equipment and therefore investment is high
2. The running costs have the potential to be high
3. There is also need to design the correct parts

With the development of the market, the diversification of molding methods and new plastic materials would be developed in the future. In order to meet the needs of the market, whether plastic mold species, structure, performance or processing are bound to faster development. What’s more such a development must keep pace with the times.

Basic instruction in how to quote plastic injection molded parts

plastic injection mold
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Plastic Injection Moulding – Explained

You will be well aware what moulding is. Moulding can be precisely defined as giving a particular shape to something in a molten or plastic state. Plastics are widely used today instead of conventional glass, wood and other materials because of its high durability. These plastics are molded into desired shapes using various techniques. The plastic injection moulding is one of the cost effective moulding techniques available today.

Little history about Plastic injection moulding

The injection moulding process is not a new concept. It came into existence by 1872. By the introduction of plastic injection moulding, the plastic industry saw multi-billion dollar earnings, with 32 % of all plastics, by weight processed by injection moulding. This has made the plastic injection moulding the best moulding method ever available.

The Principle of Plastic Injection Moulding

Thermoplastics and thermosetting plastics are the two materials that is involved in the plastic injection moulding process. Some of the polymers used in injection moulding are Epoxy and Phenolic that comes under thermosetting plastics, whereas the nylon and polyethylene comes under the thermoplastics. In this process the liquefied plastic is fed into a heated barrel where the plastic granules are mixed and forced to form a mold cavity. Once this is done, the molded cavity is cooled and then hardened.

The plastic moulding machine consists of the reciprocate screws to mix the plastic granules, while the moveable pattern molds the plastic into desired shape which takes place in the clamping part of the machine. The engineer designs the mould, and then a mold is manufactured by the mold maker either in aluminum or iron to make a desired part in a precision machine. Injection moulding is widely used for manufacturing variety of components from small parts to the entire components for vehicles.

Application

Plastic injection moulding is used to produce many parts like bottle caps, containers, plastic combs, home appliances and most other plastic products that we use today. Injection moulding is the only technique for producing many idle products in large volume and the most common method in part manufacturing. Low labor costs, materials can be used in wide range, scrap losses are minimal and high tolerances are repeatable are some of the advantages of the injection moulding techniques.

Usage of Polymers

According to BBC, in 1995 approximately 18,000 different materials were used in this process and the number was increasing at an average rate of 750 per year. Materials are chosen by the product designers, from alloys or from the previously developed blend material that has exactly the vast properties.

For injection moulding, the materials selected are based on their strength and function required for the final part. Also, the material used has different parameters for moulding and that has to be taken in account.

The injection moulding process can be of different types, namely Co-injection moulding, Fusible core injection moulding, Gas-assisted injection moulding, In-mold decoration and in mold lamination, Microinjection moulding, Multiple live-feed injection moulding and with some other types.

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Information About Plastic Injection Molding

Plastic is the most versatile material that is used in most applications today. The wide range used of this material has made a great impact in most industrial world. One of the processes in creating plastic product today is called plastic injection molding. This is a process of manufacturing plastic by using thermosetting plastic and thermoplastic substance.

The first plastic product called Parkensine was created by Alexander Parkes in 1851. This product is can be molded, heated and usually retains it shape when it is cooled, thus the downside of this is, it is extremely flammable, expensive and easy to crack. Another invention of plastic called celluloid was developed by john Wesley Hyatt. This product was an improved version of Parkes’s invention. It is through John Wesley Hyatt and his brother wherein the first molding injection machine was developed. This machine is a simpler version of today’s injection molding machine.

Plastic injection molding is commonly used for creating various parts of cars, from tiniest elements to the whole body components. This process involves feeding of material into barrel that is heated, afterwards, the material was mixed then placed into a cavity where it is allowed to harden and cooled. The product was design mostly by an engineer or an industrial engineer. After the molded product was harden and cooled, a machine called precision-machined, with the supervision of a mold-maker, is used to form the specific feature of a part of a specified product.

Aside from creating various components of a car, injection molding is also used for almost plastic goods such as bottle caps, wire pools, packaging, pocket combs and some gadget components. This process is widely used way in developing parts. It is used to produce vast amount of parts.

The common advantages of this process are low labor cost, scrap losses are minimized, vast rate of production, finishing of parts is minimized and wide range of materials are can be utilized.

Find More Plastic Injection Articles

At Metro Mold & Design, we have an impressive range of capabilities in custom plastic injection molding. We have two fully equipped molding facilities with state of the art machines that reliably produce custom plastic injection molding of small to large molded parts. For high volume injection molding opportunities we can also automate production for maximum efficiency that never compromises accuracy.
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What is Plastic Injection Molding?

Plastic Injection Molding is a fast growing process that has gained a lot of momentum in a very short span of time. There are various advantages of using plastic injection molding process. The major advantage is that it is very reliable and cost-effective. Also, this process produces smooth and finished products that require no further finishing. The equipments involved in plastic injection molding are very sophisticated and costly. They are known as injection molding machines. The machinery used are also heavy and some even weigh up to tons of kilogram. But only when these kinds of machines are used the final product turns out to be a quality product. This is so because the plastics are fed into these machines and they are heated until they become fluid. This signifies that the machines should bear up high temperature and thus comes the requirement of sophisticated equipments.

The plastic when poured, takes the shape of the cavity or the mold used and get solidified or settled in it. After some time molded material is ejected out from the cavity. The same cavity can be used to make any number of molds. The mold can be of any preferred shape. The mold has two components namely the injection mold and the ejector mold. The melted plastic resin is transferred into the mold and the ejector mold helps in ejecting the plastic part after it is solidified in the mold without any damage using ejecting pins.

The next procedure is the use of hydraulic or mechanical pressure. Air gets trapped inside the mold and this is done to release the air. This is known as the dwelling process. The air cavities are pushed to one corner of the mold when pressure is applied. Then the fluid is allowed to solidify and the mold is cooled. Finally the solidified plastic part is taken out from the mold either manually or automatically.

The plastic parts experience a change in their physical as well as chemical properties once the cooling process takes place. The most eminent design contemplation of the plastic injection molding process is the width of the mold. Usually a mold with a uniform wall thickness is favored. This helps in reducing the change in mechanical properties of the plastic part.

More Plastic Injection Articles

Injection Molding Robot

Plastic Injection Molding: Mold products by absorbing Plasticizing, Injection, Chilling, Ejection

Employing various techniques like thermoplastic and thermoset Injection Molding, blow molding, gyratory molding, compression molding, thermoforming, structural foam molding, etc

We offer comprehensive support from initial concept to final prototyping through production and finishing so that you get the best product and value for your money. Injection molding is widely used for manufacturing a variety of parts, ranging from the smallest accessory to entire body panels for industries like automotive, aerospace and agriculture. Plastic Injection Molding mainly involves following four steps:

Plasticizing: During this process we convert the polymer material from its hard granular form to the liquid form at correct melting point. The pellets or plastic powder is melted with in the machine. Powdered or palletized materials used in Plastic Injection Molding machines mainly are, Ethylene, Polycarbonate, Nylon, Polypropylene, Acrylonitrile-Butadiene-Styrene (ABS) and Polystyrene. Injection: It is an important step during overall Plastic Injection Molding process when heated fluid is forced in to the mold at very high pressure. It is fed in to the mold through a nozzle by a long screw plunger inside a heated barrel. Chilling: It involves cooling the melted fluid to allow it go gain rigid shape. Ejection: Here, we remove the cooled and molded object from the mold cavity.

Plastic Injection Molding is widely used to manufacture automotive parts like levers, gears and switches, and medical equipment components like blood analyzer, hear pump parts, orthopedic devices, etc. Plastic Injection Molding is the reason behind a variety of plastic products we use in modern world. Be it your lawn chairs or the PC monitor you have in front of you etc. Plastic Injection is very important process in the manufacturing industry to cast and mold plastic in different shapes and sizes. Almost 32% of all plastics by weight is processed by injection molding. Through Plastic Injection Molding we pass melted plastic in to a mold cavity of inverse shape and allow it to cool resulting in the desired plastic form. We can produce geometrically complex plastic products through Plastic Injection Molding

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http://www.patrickplastics.com/injection-molding.htm