What Is a Parting Line

A parting line is the place on a product or component where two or more molds met during the casting process. A number of considerations go into the placement of the parting line, with the goal of maintaining the overall integrity of the piece. Typically, as part of the finishing process, machinery will grind and smooth the parting line so it is no longer visible, if any extra material leaked into the space when the object was cast.

In a simple mold, there will be two halves that press together to create a cavity to fill with plastic, metal, or other materials. As an operator pours material into the mold, air can escape around the parting line, preventing bubble formation. When the material sets and people pull the molds apart, the finished object will drop out. It can be treated with finishing processes like sanding, painting, and so forth. Other molds may be more complex, with multiple components to address special shapes and design considerations.

When people design a mold for mass production, they want to place the parting line with care. Even operating under the assumption that it will not be visible after finishing, they need to think about the best position in terms of pulling the mold apart without damaging the product, and providing support while the molded material sets. If the parting line is too close to a fragile component, for instance, that part may deform during molding or break off when the operator removes the mold. Likewise, bad placement may prevent air bubbles from escaping, causing problems with the finished product.

If molds do not meet exactly, material will leach into the space between them, creating a situation called molding flash. The operator can plane, sand, scrape, or cut off this excess material and then smooth the underlying surface to make it match the rest of the object. This problem is more common with inexpensive molds, and in some cases, manufacturers will not bother to address it; cheap plastic toys, for example, may have a visible line around the middle, showing where the molds came apart.

In specifications for products made with molding, the technical drawings will include illustrations of the molds and a discussion about the location of the parting line. The mold maker will confirm that the designs are appropriate for the application and may make suggestions for changes to address concerns. For example, there could be worries that it will be difficult to file away any molding flash because the parting line is tucked into a corner of the mold, and thus will leave the product with a rough, unfinished appearance.

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What is High-Density Polyethylene

High-density polyethylene (HDPE) is a type of plastic made from petroleum. Since this material can be remolded by subsequent melting and shaping, it is classified as a polyethylene thermoplastic. It can also be joined in segments when welded or machined. However, it does not accept adhesives very well. Also known as polyethylene high-density (PEHD), products made of high-density polyethylene are marked by the imprint of the number “2” surrounded by the Möbius strip recognized as the universal recycling symbol.

As the name implies, high-density polyethylene is denser than most other polymer plastics, namely low-density polyethylene. This is due to its crystallization structure occurring in a linear fashion rather than branching out to form long chains of polyethylene. Instead, the lack of branching results in its carbon molecules bonding with more hydrogen molecules. This allows the final product to possess greater tensile strength, even though it is lighter than water. It also makes high-density polyethylene highly resistant to acids and solvents.

The production of high-density polyethylene does not happen by accident or natural event, however. In fact, the lack of branching during the polymerization process is deliberately induced by the addition of a type of reagent known as a Ziegler-Natta catalyst. Usually, these catalysts are derived from titanium compounds.

Since high-density polyethylene is so durable and chemically non-reactive, it has numerous applications in various industries. It is used in many different types of packaging containers, such as milk and laundry detergent bottles, as well as plastic grocery bags. It is also found in storage systems designed to store chemicals and fuels. In fact, high-density polyethylene is used to produce materials to act as chemical barriers, such as liners that are placed under landfills to help prevent soil and groundwater contamination. One of the most common uses of this material is in the manufacturing of wood plastic composites to make furniture, flooring, fencing, and landscaping materials.

In terms of environmental impact, products made of high-density polyethylene do not readily biodegrade in landfills. Such products can be recycled, though, albeit at the risk of losing some of its original tensile strength. Since this material is constructed of hydrogen and carbon, being subjected to high heat merely results in the release of water and carbon dioxide. However, additives, such as fire retardants, UV-stabilizers, and dyes, can produce other toxins. In addition, some environmental groups express concern over the potential hazard from the leeching of phthalates used in producing some children’s toys made from high-density polyethylene, such as teething rings.

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What Is Low-Density Polyethylene

Low-density polyethylene (LDPE) is a type of thermoplastic, a synthetic polymer that softens to a liquid when heated and freezes when cooled. It is made from petroleum. LDPE has a wide variety of applications because of its toughness and low reactivity at room temperature.

As a primary component of plastic bags, food and drink containers, trays and computer equipment such as disk drives, low-density polyethylene is an important plastic. It is resilient, easy to weld and shape and flexible to the point of being almost unbreakable. This makes it a popular choice for parts that need to be flexible in order to function correctly.

The resilience of low-density polyethylene is because of its chemical structure. Like other polymers, LDPE consists of repeating units of carbon and hydrogen atoms that form bonded chains. LDPE exhibits branching on about 2 percent of its carbon atoms, meaning that in some places, a hydrogen atom is replaced by another carbon-hydrogen chain. This makes LDPE’s tensile strength and intermolecular forces weaker, resulting in lower density and greater flexibility.

Linear low-density polyethylene (LLDPE) is a variety of low-density polyethylene that is widely used in commercial and industrial applications. It is composed of shorter branching structures than LDPE, which gives it a lower viscosity and the ability to elongate when stretched. LLDPE is used in plastic wrap and plastic bags where a thinner, stretchier material than LDPE is required.

LDPE is widely used in laboratory equipment. Its flexibility and translucence make it useful for wash bottles and tubing, and its chemical resistance allows it to be used in conjunction with chemicals that might corrode other materials. For example, LDPE has good resistance to acids, bases, alcohols, aldehydes and vegetable oils.

Laboratory equipment manufacturers state that LDPE can be used in temperatures as high as 176 degrees Fahrenheit (about 80 degrees Celsius) and as low as minus-58 degrees Fahrenheit (about minus-50 Celsius). It is recommended that special care be observed in maintaining LDPE equipment, because the material can be weakened by oxidizing agents and might soften and swell over time.

LDPE was initially developed as a variation on high-density polyethylene (HDPE). HDPE exhibits less branching in its hydrocarbon chains and is therefore a harder material than LDPE. It is used in some of the same products as LDPE, such as plastic bags, but it also can be found in more rigid materials such as milk jugs and bottle caps.

The global market for LDPE and LLDPE has grown rapidly since its inception during the mid-20th century. Although polymer science has continued to develop new materials to meet the challenges of packaging and manufacturing, LDPE has remained a popular material because of its versatility and durability. LDPE can also be recycled, which gives the material staying power in an increasingly environmentally conscious society.

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What Is Warpage

Warpage is a form of distortion that can occur in some materials, such as wood or plastic. This usually results from uneven stresses that can be internal or external to the material being warped. Common causes of warpage include uneven physical pressure or extreme temperature conditions placed on a given material. Sometimes, especially in woodworking practices, warpage specifically refers to a distortion from flatness; this is a problem when one needs a straight, flat board. In its most general sense, however, the term refers to any distortion from the intended shape and design of an object.

In man-made materials, warpage is often caused by residual stress in the composition of a material. Sometimes, flaws in production such as uneven cooling after manufacture or uneven distribution of molecules throughout a material cause internal stress that can lead to warpage or, in some extreme cases, cracking and further damage. Expansion and contraction of molecules occurs naturally with temperature change; problems with this occur when the expansions and contractions are not, for whatever reason, uniformly arranged throughout the material.

For many different manufacturing and shipping companies, it is very important to prevent warpage, as it can render products useless. As a very simple example, a warped board is often useless when a straight and flat board is needed; wood warping costs the logging industry millions in US dollars (USD) each year. Sometimes, warp on a product can even lead to eventual cracking and further damage to the material. Because of this, companies generally work to keep their products at relatively constant temperatures, as extremes of heat and cold can very easily cause an object to warp. They also make sure to keep products arranged in such a way that prevents excessive pressure from being placed on them.

A warpage can occur in many different ways and is described in terms of the way in which something warps. In a bow warp, for example, material becomes bent along the length of its face, giving it the curve of a bow. In a cup warp, the edges of the face of the material curve upward and are higher than the middle. A twist warp results in the two ends of the material being tilted at different angles to each other. A kink refers to a small area of warpage in which only a small part of the material is affected; this is often caused by a knot in a piece of wood or some similar imperfection.

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What Is Thermoplastic

A thermoplastic (sometimes written as thermo plastic) is a type of plastic made from polymer resins that becomes a homogenized liquid when heated and hard when cooled. When frozen, however, a thermoplastic becomes glass-like and subject to fracture. These characteristics, which lend the material its name, are reversible. That is, it can be reheated, reshaped, and frozen repeatedly. This quality also makes thermoplastics recyclable.

There are dozens of kinds of thermoplastics, with each type varying in crystalline organization and density. Some types that are commonly produced today are polyurethane, polypropylene, polycarbonate, and acrylic. Celluloid, which is considered the first thermoplastic, made its appearance in the mid-1800s and reigned in the industry for approximately 100 years. During its peak production, it was used as a substitute for ivory. Today, it is used to make guitar picks.

Sometimes, thermoplastics are confused with thermosetting plastics. Although they may sound the same, they actually possess very different properties. While thermoplastics can be melted to a liquid and cooled to a solid, thermosetting plastics chemically deteriorate when subjected to heat. Ironically, however, thermosetting plastics tend to be more durable when allowed to cool than many thermoplastics.

Thermoplastics also differ from elastomers, even though some are considered both. While many thermoplastics can be stretched to a point, they generally tend to both resist, and stay in the shape they are stretched to. Elastomers, as the name suggests, bounce back. However, the addition of plasticizers to the melt can render a more pliable thermoplastic. In fact, this is usually the case when a thermoplastic is being used for plastic injection molding or extrusion.

The specific action of a plasticizer is to lower the material’s glass transition temperature (Tg), which is the point it becomes brittle when cooled and soft when heated. Tg varies with each type of thermoplastic and is dictated by its crystallization structure. However, Tg can also be adjusted by introducing a thermoplastic into a copolymer, such as polystyrene. Until the use of plasticizers, some molded thermoplastic parts were prone to crack in cold weather.

Thermoplastics have been around for a long time, but are a huge component of everyday life today. For example, acrylonitrile butadiene styrene (ABS) is a type of thermoplastic used to manufacture sports equipment, toys (i.e., LEGO® blocks), and various automobile parts. Polycarbonate is used to make compact discs (CDs), drinking bottles, food storage containers, and eyeglass lenses, among other things. Polyethylene is likely the most commonly encountered thermoplastic and is used to make shampoo bottles, plastic grocery bags, and even bullet proof vests.

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What Is Thermoplastic Injection Molding

Thermoplastic injection molding is a process used in manufacturing to create a variety of parts and components for industries ranging from aerospace to automotive to construction. Thermoplastics, such as phenolic and epoxy, are heated into a molten resin and then injected into a mold that’s usually made from aluminum, steel or a metal alloy. The molten plastic then gets compressed inside the mold and allowed to cool. Machines remove the plastic component or piece from the mold, and this hardened part can then be used to construct a larger product, such as a child’s toy or an automobile door.

The thermoplastic injection molding industry churns out literally thousands of products and supports hundreds of industries. As of the 1990s, nearly 20,000 different types of thermosetting and thermoplastic materials were used for injection molding. Industrialists commonly use dyes and other agents to alter the properties of the molten plastic resin, such as its color, hardness, and springiness. The molds used to shape the molten plastic generally must be precut in a separate process, using sophisticated tooling procedures to properly prepare them. A device called a sprue allows the molten resin to enter the mold and fill up the cavity. Molds also are typically designed to allow air bubbles to escape. Otherwise, during compression and heating, the air bubbles might deform the plastic and even create internal burning of the finished components.

Pre-hardened steel molds tend to be more expensive but may be longer lasting; thus, manufacturers often use these harder, higher-quality steel molds for high-volume thermoplastic injection molding jobs. For more boutique industrial work, manufacturers may use aluminum molds, which can be more cost effective for scaled-down operations. To tool molds for industrial plastic injection work, manufacturers typically employ one of two time-tested processes: electrical discharge or standard machining. With the electrical discharge process, a robot applies a voltage from a tool to alter the shape of the base metal. With standard machining, a more conventional process, a machine or tool physically warps the mold into its final shape.

Manufacturers can experiment with literally dozens if not hundreds of variations in the thermoplastic injection molding process to optimize their processes. Changes can be made to the pressure applied to the mold, the speed of the injection of the resin plastic or to the geometry and structure of the molds. Other alterations may include the cooling time of the plastic, the pressure in the cavity, the composition of the dye, and the variety of plastic resin additives.

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Plastic Tooling and Molds for Injection Molding

In the current competitive world the most seen and used product would be made from plastic. It can be said that the world is cornered for plastics and it has revolutionized the line of attack that companies reflect about the manufactured parts. The best part about the plastic injection molding is that it is easy on the pocket, speedy and consistent. Manufacturing demands are determined by this constructive use along with the durability for the prevalent needs for the plastic are so. Also, you can get it done in a short span of time as you need them and startlingly they are durable as well. Above all it could be said that it is a blend of engineering proficiency with widespread computerization that makes the process done.

Now let us see about the process followed for the plastic injection molding. It is a highly effective process which is quite simple comparatively to other mechanical processes. The plastic pellets are fed into the insertion compartment of the machine through a hopper. One important process which is to be necessitated while doing this process is that it should be verified whether the fed pellets are steady and even. In order to ensure that this step is done correctly the reciprocated screw is jacked and followed because is the one which tests whether the plastic granules are even. A block in the part can disrupt the entire process so it is necessary. After this process is checked completely, then the pellets are passed through a heating element to liquefy or melt the granules. This reaches into the mold cavity by a nozzle and from that, the plastic is injected into the plastic mold where portable plates pertain pressure to ensure that the plastic becomes firm.

It is an enormously resourceful method for manufacturing a wide series of easy or intricate plastic parts with a good finish. The beauty of this is almost any sort of 2D or 3D shape can be achieved depending upon the requirement. On the other hand, draft is mandatory in most cases as the form or shape must permit expulsion from the mold. Side holes and threaded holes are likely to evade though, they obscure the tooling.

Apart from that, there are custom plastic molds which are carried out according to the customer specifications and it differs from the applications. Therefore injection molding is considered as an effective means to make custom parts which is often driven by the molding application.

The fundamental scheme in plastic molding is the insertion of molten liquid plastic hooked on a prepared set of shaped mold and then they are allowed to cool. As a final step the mold is removed to disclose the final product. The plastic tooling costs are low and in contrast the piece prices are high which falls under the plastic molding category.

In addition to using thermoplastic injection molding presses, variety of auxiliary equipment can be used to lower the cost of molding. Robots and Sprue pickers can also be used to remove parts and runners from the mold.

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Plastic Injection Molding A New Industry

When it comes to excelling in the manufacturing industry, you need to be able to keep up with all of the current trends. When it comes to ideals, such as localism and working with companies in your own neck of the woods, you must understand that the rules of game are changing. We are talking here about the new global economy, which is changing the way manufacturing is performed. In the old days, it would have been less expensive to work with companies in your own country or even in your own region, but technology has changed this old bit of conventional wisdom. You can see these changes nowhere more clearly than in the plastic injection molding industry. Mold companies are now expanding their operations to include countries all over the globe.

If you are unfamiliar with the changes in the plastic injection molding industry, it might be because you are unfamiliar with the requirements of the industry. First, consider all of the functions that you would expect from the world-class mold companies. They are expected to perform injection tooling, injection molding, assembly, and finishing. Most companies can simply not afford to have an in-house operation. This would require a lot of real estate with many different facilities. From a purely economic standpoint, this is not a viable option in today’s economic landscape.

Instead, plastic injection molding is a several step process that reaches all across the world. For example, mold companies my start with injection tooling in America. They might then outsource their work to facilities in China for the molding and accessories. The process might come to a close with assembly taking place in Mexico or India. As you can see, this is an industry that spans the globe, creating a global market place where the best bids wind, regardless of location.

When you need to have plastic injection molding work done, make sure that you are looking at only mold companies that understand this new global model. This will mean that you are getting a quick turnaround and optimum cost effectiveness. When it comes to the needs of a competitive industry, this is exactly what you should expect. You will also find that these global companies have no problems dealing with your own global expansion. For example, if you need your parts delivered to your offices in China, a top of the line company will have no problem making this delivery happen in a timely manner.

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What is Cast Aluminum

Cast aluminum is a specific metal that has gone through one of the several processes known as casting. Essentially, cast aluminum is created when methods such as die casting, mold casting, or sand casting are used to temper the aluminum for use in creating components for many different types of products. Cast aluminum is used for a number of items around the house, as well as machinery and other products that are necessary to the manufacturing of a wide range of goods and services.

One of the more common applications of cast aluminum is in the creation of cookware. Just as cast iron is used for skillets, baking pans, and other kitchen essentials, cast iron can also be used for these items. Usually created using the die cast approach, the cookware can withstand the high temperatures required to cook food properly and will remain useful for a number of years with no more than minimal care.

Cast aluminum is also used to create outdoor furniture. While not quite as popular as cast iron furniture for the lawn, cast aluminum patio furniture is somewhat more lightweight and can be moved around the space with greater ease. Patio furniture made with cast aluminum includes such items as chairs, gliders, and tables.

In addition to cookware and cast aluminum furniture, the cast metal is also used to create a number of motor parts for land vehicles as well as boats and ships. Components such as connecting rods, pistons, housings, radiator tanks, and other essentials can be created using both die casting and mold casting methods. Even components such as compressors and various types of gears may be created using aluminum of this type.

One of the main advantages to using cast aluminum is that the metal is often cost efficient in comparison to other cast metals. Along with the lower cost, the metal also retains a high degree of durability. While it is not necessarily true that cast aluminum will last as long as cast iron in some applications, the aluminum products do tend to hold up well for a number of years. The combination of lower cost and reliable durability makes cast aluminum an excellent choice for a number of metal components and products in domestic and commercial applications.

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What are CNC Machines

Computer numerical control (CNC) machines are automated milling machines that make industrial components without human assistance. This is possible because CNC machines are fed a series of instructions that are delivered to an internal computer controller. These instructions are in the form of codes that belong to the numerical control programming language.

The code used to program CNC machines is generically called G-code. However, G-code instructions are only part of the programming language. Specifically, G-codes give CNC machines the coordinates from which to hold and engage the machining tool in order to cut and shape metal to certain specifications. The entire series of codes used to operate CNC machines also include M-codes and T-Codes, which manage the CNC machine and drill tool, respectively. Tooling speed and feed controls are dictated by S-Codes and F-Codes, while X, Y, and Z-codes determine absolute position.

A standardized set of control codes for CNC machines was developed in the early 1960s in the U.S. by a trade organization known as the Electronic Industries Alliance. Roughly 20 years later, the system was revised and dubbed RS274D. Although these codes are still used across the country to assist computer-aided manufacturing (CAM), variations and additions exist among operators and manufacturers of CNC machines. In fact, operators of specific CNC machines need to be educated about the differences between manufacturer’s models to avoid a conflict in programming compatibility.

CNC machines have evolved considerably since their initial introduction into the manufacturing industry. The earliest CNC machines received code instructions through hard-wired controllers, which meant that the programming format could not be altered. However, later models were programmed via mainframe cables and floppy disks, which permitted variations in programming. At present, most CNC machines are tied into a network of computers and receive operating and tooling instructions via a software file containing the “.NC” extension. Although, the file extension varies with each machine shop, depending on its ISO certification protocols.

Today, CNC machines have graduated to encompass entire “cells” of tooling machines that can operate independently of each other. They are driven by the direct upload of CAM software files, eliminating the need for design plans to be physically drawn up. Modern CNC machines are also capable of running overnight or for several days without human supervision. In fact, CNC machines are now so sophisticated that they can dial the chief operator’s cell phone to notify him or her when a tool part breaks, and still complete other parts of the program. These features make it possible to produce thousands of parts while the machine shop is closed or while the operator is performing other tasks.

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