Your Guide To Plastic Molding

Plastics are synthetically produced non-metallic compounds. It can be molded into various forms and hardened for commercial use. Plastic molding products can be seen everywhere. Examples are jars, protective caps, plastic tubes, grips, toys, bottles, cases, accessories, kitchen utensils and a lot more.

Even the keyboard and the mouse that you use are made through plastic molding. Even the plastic parts of the chair that you are sitting on are created this way.

The basic idea in plastic molding is inserting molten liquid plastic into a ready shaped mold, for example the mold of a bottle. It will be then allowed to cool, then the mold will be removed to reveal the plastic bottle.

Plastic molding can also custom-mold a wide variety of plastic products including: garden pots, cabinets, office trays and boxes, barriers, barricades and traffic signage and displays for product and marketing promotions.

If you are planning to go into plastic molding business, you should first know the different processes. Choose from a plastic molding process that fits your budget, your expertise, and your resources. Here are basic definitions of various methods of plastic molding.

The Plastic Molding Processes:

1. Injection Molding

In Injection Molding, melted plastic is forced into a mold cavity. Once cooled, the mold can be removed. This plastic molding process is commonly used in mass-production or prototyping of a product. Injection molding machines were made in the 1930’s. These can be used to mass produce toys, kitchen utensils, bottle caps, and cell phone stands to name a few.

2. Blow Molding

Blow molding is like injection molding except that hot liquid plastic pours out of a barrel vertically in a molten tube. The mold closes on it and forces it outward to conform to the inside shape of the mold. When it is cooled, the hollow part is formed. Examples of blow molding products are bottles, tubes and containers.

Equipments needed in setting-up a blow molding business are relatively higher than injection molding.

3. Compression Molding

In this type of plastic molding, a slug of hard plastic is pressed between two heated mold halves. Compression molding usually uses vertical presses instead of the horizontal presses used for injection and blow molding. The parts formed are then air-cooled. Prices of equipments used for compression molding are moderate.

4. Film Insert Molding

This plastic molding technique imbeds an image beneath the surface of a molded part. A material like film or fabric is inserted into a mold. Plastic is then injected.

5. Gas Assist Molding

Also called gas injection molding is used to create plastic parts with hollow interiors. Partial shot of plastic is then followed by high-pressure gas to fill the mold cavity with plastic.

6. Rotational Molding

Hollow molds packed with powdered plastic are secured to pipe-like spokes that extend from a central hub. The molds rotate on separate axes at once. The hub swings the whole mold to a closed furnace room causing the powder to melt and stick to the insides of the tools. As the molds turn slowly, the tools move into a cooling room. Here, sprayed water causes the plastic to harden into a hollow part. In this type of plastic molding, tooling costs are low and piece prices are high. Cycle time takes about 40-45 minutes.

7. Structural Foam Molding

Structural foam molding is a process of plastic molding usually used for parts that require thicker walls than standard injection molding. Inserting a small amount of nitrogen or chemical blow agent into the plastic material makes the walls thicker. Foaming happens as the melted plastic material enters the mold cavity. A thin plastic skin forms and solidifies in the mold wall. This type of plastic molding can be used with any thermoplastic that can be injection molded.

8. Thermoforming

In this plastic molding process, sheets of pre-extruded rigid plastics are horizontally heated and sucked down into hollow one-piece tools. When the hot plastic solidifies, its shape conforms to that of the mold.

Tooling costs are usually low and piece prices vary on the machinery.

Plastic molding is a very technical process. It needs experts in this type of manufacturing business for it to be competitive in the market. Therefore, a very scientific and systematic study should be first made before going into this endeavor.

For more great plastic molding info and advice check out: http://www.plastics-hq.com

Article Source: http://EzineArticles.com/?expert=John_Morris

Your Business: Hourly Rate Survey

Your Business: Hourly Rate Survey

By Matthew H. Naitove

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Hourly Rates Dipped Again at Midyear

Custom injection molders' machine-hour rates dipped 1.3% on average in the second quarter of the year, according to 122 plants responding to our latest semi-annual survey. Rates have been dropping since the end of 2000. About 12% of respondents said their rates were lower in the second quarter than in the quarter before. Only 5% raised rates, and 83% did not change them at all.

For more details Click Here.

The "Top Ten" Moulding Problems

Simple ways to identify and avoid them.

There is a very useful article at the Dupont site for the top 10 problems and ways to avoide them.

http://plastics.dupont.com/myplastics/Mediator?id=529&locale=en_US

Injection Mold cost Estimator Tool

Would you like to know how much the new mold will cost you?

Here is an excellent online estimation tool.

Visit http://www.ufeinc.com/mold/estimator.html

Just fill in the details of mold size, no.of cavity etc and you can have the mold cost estimation ready instantly.

Winley Polymers Pvt Ltd.

Injection molding part cost estimator.

Here is a online utility you can use if you want to find out Injection molding cost estimate.

Just visit http://www.ides.com/costmate and fill up the details in the form that appear.

Click on "calculate" & you are done.

Hope this helps..

Winley Polymers Pvt Ltd.

Injection Molding Glossary

Mold

A hollow form or matrix for shaping a fluid or plastic substance. Injection molds have many holes drilled in the block for temperature control by means of hot water, oil or heaters. Molten plastic flows into a mold through a sprue and fills cavities by way of runners and gates.

Plastic

A natural or synthetic substance which is pliable or moldable at some stage during its forming or manufacturing.

Runner

Channels in the injection mold that connect the sprue with the various cavaties which molten plastic flows through.

Sprue
The hole through which molten material is chanelled into a mold.
The waste material filling or protruding from this hole after hardening.
The usually plastic rod or framework that secures molded objects, such as model parts or game pieces, before their first use.

Winley Polymers Pvt Ltd.

What is PET?

PET, the abbreviation for Polyethylen-terephthalat, is fully recycable and may be used for manufacturing new products in many industrial areas such as packaging for detergents, cosmetics, high-quality carpets, foils, car spare parts, pillow fillings for allergic persons and fabrics. Its versatility in the many industries therefore makes it unreplacable.



Being a polymer, polyethylene terephthalate's molecules consist of long chains of repeating units only containing the carbon (C), oxygen (O) and hydrogen (H) organic elements.

PET was first developed for use in synthetic fibres by British Calico Printers in 1941. The patent rights were then sold to DuPont and ICI who in turn sold regional rights to many other companies.(1)

Although originally produced for fibres, PET began to be used for packaging films in the mid 1960s and then, in the early 1970s, the technique for blowing bi-axially oriented bottles was commercially developed.

Bottles now represent the most significant use of PET moulding resins.

Making a PET bottle starts from the raw material: ethylene and paraxylene. These two substances' derivatives (ethylene glycol and terephthalic acid) are made to react to obtain the PET resin. The resin, in the shape of small cylinders called pellets, is melt and injected into a mould to make a preform. The preform, a sort of test tube shorter than what the bottle will be but with thicker walls, is then blow-moulded. During the blow-moulding phase, high-pressure air is blown into the preform allowing it to take the exact shape of the mould it is set into. The final product is a transparent, strong and lightweight bottle.

It is the strength of the material that contibutes to make PET the success it is. Indeed, carbonated soft drinks can generate pressure inside the bottle reaching up to 6 bar. Such high pressure however, thanks to the alignment of macromolecules (cristallisation) occurring both during the resin spinning process and the blow-moulding process, is not capable of deforming the bottle nor can it make the bottle explode.

Throughout the years, the PET industry has increasingly taken on environmental concerns, significantly decreasing the quantity of raw material needed for the manufacture of bottles. Nowadays, a 1.5 liter PET container is manufactured with just 35 grams of raw material!

Another striking feature of PET on the environmental side is that it is fully recyclable. It was in 1977 that the first PET bottle was recycled and was turned into a bottle basecup. Soon however, the fiber industry discovered the "new" material source and started using it for making textiles, carpets and non-woven. Today, even though the "bottle to bottle" recycling process is growing, the fiber market is still the major outlet for recovered PET.

PET containers form part of everyone's daily life: they contain water and soft drinks but many other sorts of liquids as well, such as detergents or soap.

The main reasons lying behind the success of PET containers is that, thanks to the molecular structure of the material set into a web, it is unbreakable. What is more, PET packaging is lightweight, transparent and resealable.

Another advantage of the material lies in its physical properties that allow for great freedom in design.

(1) Neumann, E H. Thermoplastic polyesters in Encyclopedia of Packaging Technology, ed Bakker M. John Wiley, New York 1986