Scientific Versus Traditional Moulding
Traditionally, the injection portion of the moulding process was done at one constant pressure to fill and pack the cavity. This method, however, allowed for a large variation in dimensions from cycle-to-cycle. More commonly used now is scientific or decoupled moulding, a method pioneered by RJG Inc. In this the injection of the plastic is “decoupled” into stages to allow better control of part dimensions and more cycle-to-cycle consistency. First the cavity is filled to approximately 98% full using velocity control. Although the pressure should be sufficient to allow for the desired speed, pressure limitations during this stage are undesirable. Once the cavity is 98% full, the machine switches from velocity control to pressure control, where the cavity is “packed out” at a constant pressure, where sufficient velocity to reach desired pressures is required. This lets workers control part dimensions to within thousandths of an inch or better.
Advantages And Disadvantages Of Nylon
The advantages of nylon PAs include their toughness and high heat resistance. They also have high abrasion resistance, good fatigue resistance, and noise dampening properties. With its low coefficient of friction, injected molded nylon is suitable for high friction and wear applications.
Although nylon does not offer inherent flame resistance and can burn quickly, flame retardant versions are available. Similarly, although nylon can be degraded by sunlight, a UV stabilizer can be added to improve performance. In addition, the material offers poor resistance to strong acids and bases.
Pmma Applications Grades And Brands
Acrylics are used in windows, greenhouses, solar panels, bathroom enclosures, and other transparent components for architectural and lighting applications.
You can see the ejector pin marks on this acrylic hinge if you look closely.
General-purpose acrylic, the least expensive type of PMMA, is used in commodity products rather than engineering applications. Sign-grade acrylic is up to 10 times stronger than general-purpose acrylic and provides excellent light transmission for outdoor signage. Marine-grade acrylic resists damage from continuous exposure to water and is often used by boat builders. Common brand names for acrylic plastics include Trinseo PLEXIGAS®, which is available with high heat resistance, and DuPont LUCITE®, which has excellent optical clarity and transparency.
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Nylon Applications Grades And Brands
Nylon is often used in strong mechanical parts such as bearings, bushings, gears, and slides. Its also a good choice for casings and snap-fit closures, threaded inserts, kinetic pats, jigs and fixtures. Additional applications range from toothbrushes and wheels to medical implants and electrical connectors.
Although nylon is the name of a specific type of polyamide that was developed by DuPont, this nylon polyamide is also available from other companies. Today, nylon comes in four main grades: nylon 66, 11, 12, and 46. Each has slightly different mechanical properties.
- Nylon 66 has a higher melting point and greater resistance to acids for use in chemical processing applications.
- Nylon 11 had increased resistance to dimensional changes because of its greater moisture resistance. Its used in outdoor applications.
- Nylon 12 has the lowest melting point and relatively good resistance to water absorption.
- Nylon 46 has a higher operating temperature than the other grades of nylon. Applications include engines and transmissions
Nylon grades can be filled with glass for greater mechanical strength.
What Industries Trust Ptfe
PTFE is most commonly known for its nonstick characteristics and its prevalence as a coating in food preparation products like pots, pans, and more. Outside of the kitchen, PTFE plays a significant role in a host of industries. Lets take a look at some of those industries and the key benefits at work:
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Advantages And Disadvantages Of Polyoxymethylene
Injection molded POM combines excellent rigidity with thermal stability and a low coefficient of friction. It also has low water absorption and good chemical resistance. Two main types of POM plastics are available: homopolymers and copolymers. This gives engineers and designers a choice of acetal materials with different properties.
In its pure form, POM has low impact strength and a very high rate of thermal expansion. Mold shrinkage is relatively high and acetals do not resist UV light. POM plastics that are homopolymers provide higher hardness and tensile strength. However, all POM plastics cannot be fire-rated to a standard such as UL 94.
Molds: Make ’em Rugged
Speed is one of the key attributes of successful thin-wall molding. Faster filling and higher pressures are required to drive molten thermoplastic material into thinner cavities at a sufficient rate to prevent freeze off. If a standard part is filled in 2 sec, then a reduction in thickness of 25% potentially can require a drop in fill time of 50% to just 1 sec.
One benefit of thin-wall molding is that as wall sections drop, there is less material to cool. Cycle times can drop by 50% with aggressive wall-thickness reduction. Careful management of the melt-delivery system can keep runners and sprues from diminishing that cycle-time advantage. Hot runners and heated sprue bushings are often used in thin-wall molding to help minimize cycle time.
Mold material should be reviewed too. P20 steel is used extensively in conventional applications, but due to the higher pressures of thin-wall molding, molds must be built more robustly. H-13 and other tough steels add an extra degree of safety for thin-wall tools.
However, robust tools cost moneypossibly even 30% to 40% more than a standard mold. Yet the cost is often offset by increased productivity. In fact, the thin-wall approach is frequently used to save money on tooling. A 100% increase in productivity can mean that fewer molds need to be built, thereby saving money over the life of a program.
Here are some more tips on tool design for thin walls:
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What Are The Ingredients In Eyelash Adhesive
The main ingredient in all lash adhesives is cyanoacrylate, a fast-drying, glue-like chemical bonding agent. This compound is made from cyanide and acrylate, which both sound like things you definitely shouldnt put near your eye, but stay with me here. Cyanide is a carbon atom that is triple-bonded to a nitrogen atom.
Defects Typically Related To Material Use Or Storage
Injection molding defects can often originate from the material itself or how the manufacturer stores and handles the material prior to the production process. These defects can range from minor aesthetic issues to compromised strength of the finished component. Serious safety concerns may also result, depending on the intended application of the product affected.
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Is Ptfe Can Be Injection Molding
Our company often receives the customer phone to ask the PTFE Resin and PTFE Powdercan injection molding? Today Shandong Hengyi New Material Technology Co., Ltd gives you the problem of whether polytetrafluoroethylene can be injection molding. Polytetrafluoroethylene can not be injection molding, Shandong Hengyi New Material, can provide injection molding grade Polytetrafluoroethylene is used to solve the product demand. The injection polytetrafluoroethylene is called fusing polytetrafluoroethylene , its performance is the same as polytetrafluoroethylene , and the fusing polytetrafluoroethylene can be molded in injection.
Polytetrafluoroethylene can not be produced by injection molding. Polytetrafluoroethylene has a high melting viscosity and is sensitive to shear in high temperature amorphous state and easy to produce melt rupture. Therefore, polytetrafluoroethylene can not be used by molten extrusion, injection molding and other conventional thermoplastic molding processes. Polytetrafluoroethylene can only be cold. The manufacturing process of press forming is moulded, plunger or screw extruding, but fluxing polytetrafluoroethylene can be molded by injection.
Shandong Hengyi New Material Technology Co., Ltd sells the main properties of injection molded polytetrafluoroethylene :
4.The vermicular and compressive strength of PFA can be better than polytetrafluoroethylene, with high tensile strength, good elongation at 100-300%. and excellent radiation resistance.
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Pc Applications Grades And Brands
Polycarbonate is used for machinery guards, clear or tinted windows, diffusers and light pipes for light emitting diodes , and in clear tubing. This material can also be used to produce clear molds for urethane and silicone casting.
Polycarbonate can be filled with glass and compounded with ABS for increased impact resistance. Some grades contain a relatively small percentage of stainless steel fiber. Popular brand names include SABIC Lexan®, which is available in flame-resistant versions, and Covestro Makrolon®, which has glass-like transparency.
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Injection Molding Defects Caused By Poor Mold Design Or Maintenance
Defects can be introduced into molded products by issues with the mold tooling itself. Certain defects are likely to occur when the mold is poorly maintained or designed. Especially in the latter case, these defects can be difficult or costly to address in future production runs when its necessary to completely overhaul the mold.
Blended Plastic Injection Molding Materials
Although theyre the most common types, the materials listed above arent the only choices that you have. Depending on your specific requirements, you can also choose blended plastics that combine the best properties of two different polymers. Various blends are available, but the most common types are PC/ABS, PC/PBT, and PPE/PS.
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The Two Ways To Process Teflon For Seals
There are different grades of Fluoropolymers that can be used to manufacture seals. There are melt processable fluoropolymers, which are rarely used in the seal manufacturing process due to cost, and granular PTFE.
Melt processable fluoropolymers allow for injection molding, and exhibit many of the same characteristics as granular PTFE. But the first grade doesnt allow for the flexibility of molding and machining, which is why most of our seals are made from granular PTFE.
Use The Biggest Gates Possible
PEEK likes big gates. Gate size is dependent on the part volume, number of cavities and component geometry. PEEK is a semi-crystalline polymer and exhibits much higher shrinkage compared to an amorphous thermoplastic. Moreover, cooling from a much higher processing temperature to ambient causes more shrinkage compared to lower temperature processing polymers. Using the biggest gates possible will enable that you fully pack out your component. At Victrex, we have a general rule called the 2/3rds rule of the maximum section thickness of your component. Depending on the grade of PEEK that youll be molding this might be a minimum of 1mm for unfilled PEEK and 2mm for compounds. Gate designs such as tab, side or fan gates are most commonly used. Submarine or tunnel gates can be considered for very thin walls or small parts but tend to lead to freeze off during molding of bigger parts.
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Milling Granular Ptfe For Seals
All granular PTFE starts out as standard flow which means its the consistency of flour. While it can flow into a seal mold, it pours much like flour, which can be clumpy.
Standard flow can be blended with fillers to help improve some physical properties, such as wear, but can degrade tensile and friction. Tensile strength is usually not a problem, as most seals are in compression.
Fillers will increase friction slightly. When fillers are mixed, or blended, into the base resin, theyre milled to ensure uniform dispersion within the compound thats being created.
During this milling process, the mixture begins to get warm. Keeping the temperature low ensures that the fillers can be uniformly dispersed within the mixture.
If the temperature does rise to the point in which the compound will no longer flow in the mill, clumping can occur. Materials will generally have multiple passes through the mill, but too many passes will begin to degrade the physicals in the base resin.
Allowing the compound to rest after filling will allow the bulk temperature of the compound to return to room temperature. This helps the molder pack the material into the mold.
If the compound is too warm during the molding process, voids can form in the mold, which will result in cracking in the seal.
The Ten Most Common Plastic Injection Molding Materials
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07.29.2021 Material Guides
Time to read: 13 min
Plastic injection molding materials have names that sound like terms from chemistry class. Its hard enough that polyethylene rhymes with polypropylene, which has an abbreviation thats similar to polystyrene . Choosing the right injection molding material also means knowing your application requirements, which can change between prototyping and production.
Fortunately, you dont need a PhD in chemistry to make the right material choice. There are many factors to consider, of course, but it all starts with the basics: the names and abbreviations of leading materials, their advantages and disadvantages, typical applications, and common brands and grades.
There are ten commonly used plastic injection molding materials:
For each injection molded plastic, the following sections explain what you need to know.
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Manufacturing And Qc Blog
- Manufacturing and QC blog
- 11 Injection Molding Defects and How to Prevent Them
Theres a lot of room for expensive errors when it comes to injection molding. Quality issues in injection-molded products can range from minor surface defects to more serious problems that can affect the safety, performance and function of the product. They can be caused by problems related to the molding process, material use, tooling design or a combination of all three.
But as with any quality problems, knowing how molding defects arise is half the battle . As an importer or manufacturer of injection-molded products, some knowledge of common molding defects and how to avoid them can help you cut costs related to unsellable goods and product returns.
Lets look at the most common quality defects related to injection molding, what causes them and what you can do to prevent them.
Injection Molding Of Fluoropolymers: What You Need To Know
Fluoropolymers are used in multiple industries, including aerospace, transportation, chemical and petrochemical processing, pharmaceutical, medical, telecommunications, and electronics where they are used for seals, gaskets, bushings, bearings, hoses, tubing, wiring, and even fiber optic cladding. There are multiple ways to manufacture parts and components made from fluoropolymers, and injection molding is one of them.
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Advantages And Disadvantages Of Polycarbonate
Polycarbonate is extremely durable and 250 times stronger than glass. With its predictable and uniform mold shrinkage, this injection molding material offers precise dimensional control. PC plastic is also lightweight and has excellent optical properties to support light transmission.
Because it contains BPA, injected molded polycarbonate is not recommended for food preparation or storage. It also requires high processing temperatures, which can make it more expensive to mold. Polycarbonate is not scratch resistant either.
Advantages And Disadvantages Of Acrylics
Acrylics have a high tensile strength to withstand loads, wont absorb odors, and can be held to tight tolerances during injection molding. The material also resists sunlight and weather, which makes it suitable for outdoor use. Because it doesnt degrade when in contact with water, PMMA wont release Bisphenol A , a chemical in many plastics that has adverse effects on human health.
Acrylics have a few important limitations. They cost more than glass and scratch more readily. Theyre also easily stained by greases and oils. In addition, PMMA has a service temperature that is too low for some industrial applications. Injected molded acrylic lacks strong solvent resistance and can be prone to stress cracking under especially heavy loads.
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Tpu Applications Grades And Brands
Injection molded TPUs are used in footwear, gaskets, caster wheels, and sporting goods. Applications also include cases or enclosures for electronics and medical devices. In medical applications, TPUs are sometimes used instead of polyvinyl chloride , a plastic that may cause skin irritation.
Thermoplastic polyurethanes come in commercial, medical, and industrial grades. There are three main classes of TPU materials: polyester, polyether and polycaprolactone. Trademarked products are available from manufacturers such as Lanxess, Lubrizol, Texin, and Ultralast.
Advantages And Disadvantages Of Polyethylene
HDPE, LDPE, and PET are all low-cost plastics that resist both moisture and chemicals. LDPE is softer and more flexible than HDPE, which is an opaque material. Like LDPE, PET can be as clear as glass. Engineers and designers like these materials because they provide a range of choices in optical clarity and other properties.
PE plastics are limited by poor UV resistance and cannot withstand high service temperatures. HDPE parts are difficult to mold with thicknesses of less than .020-in. With injection molded LDPE, close tolerances are hard to achieve. PET absorbs significant water and requires resin drying, which adds to production costs.
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Tpe Applications Grades And Brands
Injection molded TPEs are used in footwear, medical devices, auto parts, and pet products. Automotive applications include weather seals and shock dust boots. Medical applications include breathing tubes, valves, catheters, and ventilation masks.
ISO 18064 defines generic classes of commercial TPEs. There are many different manufacturers and brand names, including Teknor Apex Telcar®, Kraiburg HIPEX®, and Dynaflex from Avient . Healthcare grade TPEs are available.
Alternatives To Molding With Teflon Thermoplastics
Teflon thermoplastics are commonly used for injection molding, however there are several alternatives available that provide similar weldability, dialectic properties, weatherability and temperature resistance.
Springboard has been producing high quality, high precision injection molded parts from thermoplastic materials since 1995. With our extensive experience and expertise, we can deliver parts and components that match your designs exactly and meet the tight tolerances your industry or application requires.
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Pe Applications Grades And Brands
PE plastics are known for their use in milk bottles , plastic films , and water bottles however, these products are not injection molded. They are made using a different type of molding called blow molding. Examples of injection molded PE include childrens toys, toolboxes, electronic wire and cable insulators, and medical device components.
This tool box is an example of injection molded polyethylene.
PE plastics come in numbered grades where higher numbers generally indicate higher densities. For example, HDPE 500 has a higher density than HDPE 300. Both grades have a higher density than LDPE, which also uses a numbering system for grades. BASF and DuPont are two of the leading suppliers of PE for engineering rather than general-purpose applications.
