What is Polyethylene

Polyethylene is a type of polymer that is classified as a thermoplastic, meaning that it can be melted to a liquid and remolded as it returns to a solid state. As the name implies, polyethylene is chemically synthesized from molecules that contain long chains of ethylene, a monomer that provides the ability to double bond with other carbon-based monomers to form polymers. Polyethylene is known by other, non-official names, such as polythene in the United Kingdom. In addition, it is sometimes spelled as polyethylyne, or abbreviated to simply PE.

The first laboratory creation of polyethylene occurred in 1898 by accident at the hands of Hans von Pechmann while applying heat to another compound the German chemist previously discovered — diazomethane. Ironically, the synthesis of polyethylene via extreme heat and pressure in an industrial setting was again made by accident, but 35 years later. A few years later, another chemist employed by the same England-based chemical company devised a method to consistently produce polyethylene under the same conditions. As a result, polyethylene became the primary source of low-density polyethylene (LDPE) production in 1939.

While polyethylene is essential to the economic health of the plastics industry, most consumers readily recognize the role it plays in everyday life. In fact, this substance is found in many ordinary household items, such as food wrap, shampoo bottles, milk containers, toys, and the common plastic bag used to tote groceries home from the store. However, polyethylene is also present in numerous other products that contain plastic components. For instance, it is used to manufacture artificial knee and hip replacement parts, bulletproof vests, and even glassy flooring for ice skating rinks.

Polyethylene may fall under one of several types. The distinction between them is determined by its molecular weight and branching, which is affected by its crystallization. LDPE is an example of branched polyethylene since its carbon molecules are attached to long chains of polyethylene instead of hydrogen. Otherwise, a linear structure of carbon to hydrogen occurs, which is known as high-density polyethylene (HDPE). However, further variances in structure and molecular weight produce other forms, such as ultra high molecular weight polyethylene (UHMWPE), medium-density polyethylene (MDPE), or very low-density polyethylene (VLDPE).

While polyethylene may help to make numerous useful and durable products possible, its environmental impact is cause for concern. For one thing, it does not readily biodegrade and can reside in a landfill for hundreds of years. However, diligent recycling may significantly reduce this problem. In addition, scientists are exploring the possibility of employing Sphingomonas, an aerobic bacteria shown to shorten biodegrading of some forms of polyethylene to just a few months. Environmental preservation efforts have also led to the development of bioplastics, with the aim of synthesizing polyethylene from ethanol obtained from sugarcane.

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What is Nylons

The term “nylons” refers to the group of plastics known as polyamides. Nylon is used in the production of film and fiber, but is also available as a moulding compound.

There are many types of nylon available (e.g. nylon 6, nylon 66, nylon 6/6-6, nylon 6/9, nylon 6/10, nylon 6/12, nylon 11, nylon 12). The material is available as a homopolymer, co-polymer or reinforced. Nylons may also be blended with other engineering plastics to improve certain aspects of performance. Nylon is well suited for processing via injection moulding, rotational moulding, casting or extrusion into film or fiber.

Chemical Composition

Its properties are determined by the R and R’ groups in the monomers. In nylon 6,6, R’ = 6C and R = 4C alkanes, but one also has to include the two carboxyl carbons in the diacid to get the number it donates to the chain.

A.K.A.

Polyamides, PA

Properties

The majority of nylons tend to be semi-crystalline and are generally very tough materials with good thermal and chemical resistance. The different types give a wide range of properties with specific gravity, melting point and moisture content tending to reduce as the nylon number increases. Nylons can be used in high temperature environments. Heat stabilized systems allow sustained performance at temperatures up to 185oC.

Physical Properties: Value:
Tensile Strength: 90 – 185 N/mm2
Notched Impact Strength: 5.0 – 13.0 Kj/m2
Thermal Coefficient of Expansion: 80 x 10-6
Max. Continued Use Temperature: 150 – 185 oC (302 – 365 oF)
Melting Point: 190 – 350 oC (374 – 662 oF)
Glass Transition Temp. (Nylon 66): 45 oC (113 oF)
Density: 1.13 – 1.35 g/cm3
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What Is Prototype Tooling

Prototype tooling is a way of creating a prototype from a design or three-dimensional (3D) model; in many regards, it is the same as regular tooling. Traditional tooling techniques usually are used with prototype tooling, but 3D printing also can be used to form the prototype for some needs. While this is similar to regular tooling, there are differences in how the prototype is put together and its overall functionality. The tooling company is producing a small number of copies, so the per-copy rate is much higher than with regular tooling.

Tooling is a method of working with materials in which the materials are cut and shaped to make a specific form. For example, to make a screw, a chunk of metal is made into a cylinder and then a spiral is cut into the bottom half of the metal. In most regards, this is what prototype tooling is; the materials needed for the prototype are cut and shaped to make a prototype copy. Aside from functionality issues, another major difference between prototype and regular tooling is the output amount, because only a limited number of copies are made for the prototype.

While traditional tooling commonly is used for prototype tooling, 3D printers also can be used for some prototypes. Simple functionality may be replicated with this method, but advanced functionality is difficult. This is more like a mold that is replicated from a 3D model; this means 3D printing is a useful tooling technique when plastic is being used.

There are some differences between prototype tooling and regular tooling that may keep a prototype from being used safely and properly. If the prototype is supposed to be functional, with moving parts, then this usually will be downplayed to make the prototype easier and faster to tool. This means the functional parts may not be included, or they may be simplified so the functions can briefly be displayed to interested buyers. The parts usually are not fastened as securely, so the prototype may not be safe for extended use.

Regular tooling often is expensive, but because there are so many copies being made at once, the per-copy rate usually is relatively affordable. It is harder to use the tooling machines for a short run, especially if the prototype tooling is unlike any other part, so the per-copy rate often is much higher. This means the inventor may have to pay a lot of money to get the prototype properly tooled, even if the prototype is similar to existing products.

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What Is a Prototype Mold

A prototype mold is a term that most designers and manufacturers are familiar with due to the fact that it is connected to the process of bringing a concept to life. Usually, when industrial or product designers have a concept for a product, they will go through various stages in the quest to take the concept from a mere idea to a more realistic representation of the product in the form of something tangible that represents what the product will look like after it has been manufactured. While a prototype mold is used to create a representative object that fully mirrors the concept the designers have in mind, it is different from a production mold in the sense that the prototype mold is far less costly and less permanent than the production mold.

The prototype mold is created in such a fashion that allows for any further amendment to the product due to the fact that the prototype mold is only used when the product is still being fine-tuned. For example, a designer that has a concept for a type of desk lamp would first use the mold to see what the finished product will actually look like. It is during this phase that the designer can add any additional touches to the product in order to make it conform to the idea for the product. Assuming the results of the sample from the prototype mold are not satisfactory, the designer will make several changes to the mold in order to produce something that looks more like what the a designer has in mind. This is different from the production mold in the sense that the production mold is used for mass production and is more permanent than the prototype mold due to the fact that at this point the objective is not to fine tune the design, but rather to go into full production.

One of the reasons why a designer might choose to use a prototype mold before using the production mold is due to the complexity of the concept, something that might require a lot of attention to details in order to achieve the design. As such, the prototype designing phase will consist of several incremental steps until a satisfactory result has been achieved. Depending on how complexity of the design, some designers can create the mold themselves, or they can engage the services of prototype developers.

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What Is an Injection Molding Prototype

In the process of manufacturing, the term injection molding prototype can refer to two distinct things. An injection molding prototype can be a custom injection molding part. The term can also refer to the original part used to create an injection mold from which duplicate parts may be cast. In either case, a prototype is usually either a singular part or a part from an early series of developed products.

The first usage of the term refers to products of the injection molding process. These parts are usually one of a kind and created for a specific purpose. The injection molding prototypes produced in this manner do not require mass production, and the production numbers are limited.

While the first usage of injection molding prototype is fairly straightforward, the second requires a bit of explanation. The prototype used to create injection molds has been employed since the early history of injection molding. Similar to the lost wax method of casting, injection molding prototype casting utilizes the original prototype to shape and form the injection mold. Machines force molten plastics into a mold made in the exact negative of the original injection molding prototype. By creating molds in this way, an exact duplicate of the original part can be made.

This process is often accomplished by the same techniques used to create lost wax casting molds. The injection mold maker uses vulcanized rubber to make an exact negative mold of the injection molding prototype. The mold maker uses this negative to create injection molding dies for long production runs. The worker may also use the original mold for projects that do not require mass production.

The injection molding prototype may be made from wood, metal, ceramic, or other materials. The only standard for prototype product choice is that the material must be able to withstand the heat of the mold making process. This wide variance in materials makes it possible to create prototypes in a reasonably low-cost manner.

In some cases, the injection molding prototype of an exact part might be too detailed for proper casting of injection molded parts. In these circumstances, details such as threading or cut-aways may be omitted from the injection mold and later tooled into the individual work pieces. While the tooled components will not have the same strength as purely injection molded pieces, this step can eliminate trouble areas in the casting process.

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What Are the Different Plastic Injection Molding Jobs

Plastic injection molding jobs are typically located in the manufacturing industry. The process required to qualify for this type of job includes post-secondary training or significant workplace experience. Plastic injection molding is a term used to describe the process for creating formed plastic products. Plastic products are very flexible and are used to meet a range of different needs — from consumable to hard products.

The process of plastic injection molding requires the use of large, complex machines. A chemical mixture is heated, turned, and then forced to fill a mold cavity. The mixture cools and hardens within the cavity, taking on the shape and form of the mold. This process is very flexible and can be used to make everything from plastic toys to car doors.

There are three different types of plastic injection molding jobs: production line technician, maintenance mechanic, and quality inspector. All these positions require staff who have a fundamental understanding of injection molding equipment, concepts, and procedures. The typical training program is one or two years in length and is available at the community college level.

A production line technician is responsible for the operation of the injection molding machine, monitoring the flow of liquid plastic and ensuring the smooth performance of all the machines and tools used. This position is usually an eight-hour shift, with most operations working on a continuous basis. The technician is expected to control the machine, perform minor maintenance, and make adjustments as necessary for continuing operation.

Of all the plastic injection molding jobs, maintenance mechanic has the most parallels with other manufacturing positions. In this role, the mechanic is responsible for complete tear down, installation, cleaning, and major repairs. Most facilities ensure there is at least one maintenance mechanic on duty at all times. The availability of this type of staff member is critical to ensuring production interruptions are minimized.

The role of quality inspector is to visually and scientifically test a random selection of products off the production line. These tests are conducted against a standard set of tests. All results are documented and any variations outside the accepted standards are highlighted and subject to further review. This type of job is best suited to someone who is detail oriented.

In general, plastic injection molding jobs are well compensated, but often require rotational shifts and working weekends. Talk with career center staff about the different possibilities and career advancement opportunities. Most firms require additional training to advance into management positions.

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What Is the Plastic Injection Molding Process

When thermoplastic and thermosetting plastic materials are produced, this process is referred to as the plastic injection molding process. In order to create these products, material must be heated, mixed, and placed inside of a mold. When the mold cools, the material is extruded resulting in specific objects.

While plastic may seem like a relatively new invention, the first plastic object was actually created in 1851. A British inventor by the name of Alexander Parkes created a material that was then called Parkesine. Even though Parkesine proved to be both durable and innovative, it was also highly flammable. Thus, Parkes’ invention did not enjoy a long lifespan. In 1868, an American inventor by the name of John Wesley Hyatt developed a similar product that he dubbed celluloid. After joining forces with his brother, Hyatt created the first injection molding contraption in 1872.

This injection machine revolutionized the way that objects were made. Items such as buttons, hair combs, and collar stays were a result of the Hyatt brothers’ injection molding machine. When the 1940s rolled around, the plastic injection molding process became an essential part of the manufacturing business.

Consumers were demanding inexpensive products. In turn, these products also had to be inexpensive to produce, causing plastic items to drastically grow in popularity. The plastic injection molding process changed as a whole when the first screw injection machine was created in 1946. James Watson Hendry’s screw injection machine allowed manufacturers to have more control over plastic injections. The screw injection machine proved to be such an advancement that many of the machines used today still function in the same manner. Once it was observed that the plastic injection molding process could be entirely precise, plastic replaced other materials such as steel and ceramic.

Today, nearly every plastic item — milk caps, car dashboards, combs, phones — is created through the plastic injection molding process. In many different ways, plastic has replaced most other materials. Due to its flexibility, versatility, and reliability, plastic objects are popular around the globe.

The plastic injection molding process makes it possible for manufacturers to create thousands of products at once. In addition, labor costs are relatively low within the plastic industry, and parts can be refined following the injection process. The main drawback to injection molding equipment is that this equipment is often expensive to maintain and purchase. Still, plastic proves to be one of the most widely produced materials in the world.

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What Is Custom Injection Molding

Custom injection molding is the fabrication of plastic components using customized design specifications. This service is offered by many manufacturers of plastics. The pricing varies, depending on the type of project involved, but generally custom injection molding is more expensive than using standardized components. People can present manufacturers with their specifications and the number of components they need to get a pricing estimate.

In injection molding, heated plastics are shot into a mold. As the plastic cools, it conforms to the shape of the mold and sets in place. The molds can be opened to release the components and they can be finished with trimming, sanding, and other measures if necessary. Injection molding is a very cost effective way for making plastic components, as molds can be easily swapped out as needed and people can produce plastics in different colors and with other characteristics by adjusting the mixture used in the injectors.

For custom injection molding, a mold is fabricated for a specific purpose, like encasing a given car part. The customer also specifies the characteristics of the plastic, including the level of hardness and flexibility, heat and cold tolerance, and color. A mockup will be made with the mold to make sure it works, and then the plastics company can start a production run, limiting the run to the number of components necessary. Usually, custom injection molding gets cheaper with large runs, as the cost for producing the mold and formulating the plastic is the same with one part or one million parts.

Once the custom injection molding is finished, the mold can be put in storage in case there’s a future need. It can also be returned to the client in some circumstances, and in others may be destroyed. People can discuss what they want to happen with the mold during the initial consultation with the manufacturer. One advantage to keeping molds on file at the manufacturer with notes about the formulation used is the ability to easily generate new parts for replacements and repairs.

As with other custom fabrication jobs, it is advisable to consult several manufacturers to get price estimates on custom injection molding. It can also be helpful to seek out manufacturers specializing in similar kinds of plastics products, as they can be less expensive and may produce pieces of higher quality because they are familiar with the work. Someone who wants custom toys, for example, might not go to a manufacturer who focuses on producing plastic parts for medical equipment.

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What Is Metal Injection Molding

Metal injection molding (MIM) is a process by which metal is powdered, mixed, and placed into a mold to create solid parts and pieces of equipment. The mixture of powdered metal and binding material, known as the feedstock, is limited in quantity, making metal injection molding ideal for small, detailed parts. Applications of this process include machinery parts, dental tools, and firearm equipment, and they all generally involve small and complex parts.

Powder metallurgy is the technique that determines which types of metal can be made into a powder for the metal injection molding process to occur. Different strategies for creating a metal powder are available, such as physical deposition, grinding, atomization, chemical reactions, or centrifugation. The type of powder strategy is heavily dependent upon on the type of metal to be powdered and its specific qualities.

Once the metal powder has been produced it is mixed with a binder, which is a material made up of various waxes and plastics. The resulting mixture, called the feedstock, is then ready to inject into the mold. Due to the similarities between the feedstock and the molten plastic used in regular injection molding, the same injection molding equipment can be used for metal injection molding. The feedstock is injected into the molding equipment in a small amount called a shot, which is then allowed to cool inside the mold.

After the cooling has been completed the binding material is partially removed from the part, usually with a solvent or chemical reaction, but occasionally the part is heated to melt off the binder. The part now contains a significant fraction of empty space that comprises about 2% to 4% of the total volume in a stage of the process known as the brown stage. Metal is then made stronger and denser through a sintering process. During sintering, the metal is heated to a temperature just shy of its melting point, until the surface of the metal particles fuse together while still maintaining the structural integrity of the part. The end result is a metal part that contains a solid density of up to 99%.

Once smaller modifications have been made, the part is completed and ready to be used. Since metal injection molding involves the use of molds, it is a more flexible technology and ideal for complex, intricately designed parts. Other metal technologies often require high costs to achieve the same resulting products, so metal injection molding is becoming an increasingly popular technique for manufacturing these parts.

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What Are the Different Types of Injection Molding Equipment

Injection molding equipment, also called injection presses, injects molten plastics into a mold and then cools the plastic and extracts the freshly made parts. The equipment itself is often identified as belonging to one or more different types. Types of injection molding equipment include vertical and horizontal presses, injection cylinder and injection screw presses, hydraulic and electric presses, and other presses rated by the amount of pressure they can apply to molds. There are also hot and cold runner molding systems used with injection molding equipment.

Sometimes injection molding equipment is identified as horizontal or vertical. This identifies the way that the injection press holds the mold in the machine. For a given application, this may be a critical factor for a manufacturer. If the parts being produced are large, gravity may be needed to help extract the part from the machine. If the parts are small, they may need to be extracted horizontally onto a table or another device to further the manufacture of the parts.

The way the molten plastic is injected into the mold can also identify the type of molding equipment. Some kinds use a cylinder that collects the molten plastic in a chamber, then drives a piston down on the chamber to create the pressure to inject the plastic into the mold. The other system involves a long, heated barrel that contains a screw. The plastic is fed into one end and driven down the barrel by the screw melting the plastic as it goes along. The pressure needed to inject the plastic into the mold is created not by a cylinder, but by pressure created by the screw.

Some injection molding equipment is identified by how the pressure needed to keep the different parts of the mold together is created. In hydraulic systems, a series of hydraulic cylinders moves the pieces of the mold and creates the pressure to hold them steady while the plastic is injected. In other types of injection molding equipment, the molds are moved and held together by a series of electric motors. Higher pressure mold systems tend to use hydraulic, and lower pressure systems tend to use electric; there is a wide area of overlap where either may be suitable for a given application, however.

The molds used in injection molding can be of two general types: hot runners or cold runners. Runners are the passages in the mold that the molten plastic travels to reach the various chambers that it needs to fill to create the part. If the molding equipment cools these runners, it is referred to as a cold runner system. If the runners are heated, the equipment is called a hot runner system.

When defining injection molding equipment by type in the plastics industry, the primary feature needed for a given application tends to determine how the machine is referred to. Those who use hot runner systems will often say they use a hot runner injection molding machine even though it’s also horizontal and electric. Those who make large plastic parts may refer to their machines as vertical even though they also have hot runner and hydraulic systems. As there are many types of injection molding equipment, each piece of equipment is actually one of many different types and can be unique, depending on the combination of systems it possesses.

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