What Is Injection Molding
Injection moulding is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Injection moulding can be performed with a host of materials mainly including metals (for which the process is called die-casting), glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed (using a helical screw), and injected into a mould cavity, where it cools and hardens to the configuration of the cavity.[1]: 240 After a product is designed, usually by an industrial designer or an engineer, moulds are made by a mould-maker (or toolmaker) from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection moulding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. Advances in 3D printing technology, using photopolymers that do not melt during the injection moulding of some lower-temperature thermoplastics, can be used for some simple injection moulds.
Advantages of Injection Molding
Ability to Produce Detailed/Complex Geometries
With the right tool design and a scientific molding approach to process optimization, injection molding can help manufacturers produce highly complex, detailed plastic parts in large volumes with virtually no deviation.
Efficiency
An experienced custom injection molding partner provides manufacturers with a decided advantage in terms of efficiency. The molder's teams — from engineering through production — likely have decades of expertise to draw upon when determining how to optimize part design and manufacturing. Implementing best practices generally streamlines time and cost commitments.
Strength & Versatility
Of all the benefits of injection molding, the steady increase in the strength and versatility of plastics may be most appreciated. Today's lightweight thermoplastics can withstand even the harshest environments on par with — or better than — metal parts. Additionally, plastics are versatile. There are more than 25,000 engineered materials to choose from for complex injection molding applications. High-performance blends and hybrids can also be formulated to meet very specific part requirements and characteristics, such as high tensile strength.
Ability to Simultaneously Use Multiple Types of Plastic
Complex part designs commonly require components made of different materials. While seemingly a matter of simple choices, safely combining plastics can be extremely complicated. The plastics expertise of the molder's project engineers guides compatibility, and helps prevent defects, injury risk, and warranty claims.
Cost Savings
There are several ways that injection molding can help OEMs experience lower costs, from plastic part consolidation to overmolding. However, the #1 way to manage costs is through collaboration between OEM and injection molding engineering teams well before production is set. Focusing on Design for Manufacturability (DfM) and other detailed processes during the design phase significantly reduces the number of problems sometimes encountered with moldability — minimizing the need for expensive tooling changes, downtime, and other production delays.
Precision
For complex part designs requiring tight tolerances, injection molders can achieve designs accurate to within +/- .001 inches. These measurements aren't only possible; they're repeatable across production runs and equipment.
Shorten Product Development Time
Different skill sets held by injection molding engineers can help OEMs achieve a shorter product development timeline. Doing so means faster production cycles and getting defect-free parts to market quickly — a decided competitive advantage for manufacturers.
Multiple Finishes
A smooth surface is the desired final look for most injection molded parts. However, it's not the appropriate finish for every application. Depending on the physical and chemical properties of the plastics used, injection molding allows for surface finishes that don't require secondary operations — from matte finishes and unique textures to engraving and more.
High-Output Production & Consistency
High-output production of complex plastic parts — especially those with tight tolerances — requires a consistent, repeatable process. Injection molding is an ideal solution since parts are produced using the same tooling, combined with the molder's continuous improvement practices that incorporate current leading-edge technologies.
Color Control
From clear to any color an OEM needs, injection molders can make it happen by aligning plastics, additives, and biocompatibility to achieve desired coloration. Should multiple colors be needed in one product, a molder with proven overmolding and multi-material injection molding experience is the best bet for quality solutions.
Flexibility
Injection molding is all about flexibility, whether attributed to some plastics' properties or the ability for OEMs to customize solutions that meet specific project requirements. Injection molding gives OEMs freedom in design choices — especially when compared to metal.
Reduced Waste
We're proud of our ongoing green initiatives that positively impact the environment. However, our commitment to the planet isn't limited to corporate social responsibility. We understand the ecological and economic benefits of injection molding sustainable practices — such as using plastic regrind, which minimizes waste and directly benefits OEMs.
Lower Labor Costs
Much of the injection molding process is automated by machines and robots, and controlled by a sole operator or technician. This streamlines labor costs and also greatly reduces the risk of rework caused by part defects or human error — both of which save OEMs money.
Lightweighting
Popularized in the automotive industry, lightweighting is the practice of substituting metal parts for parts made from high-performance plastics. The goal is to reduce overall product weight in order to achieve certain manufacturability and operational goals. In the auto industry, for example, lighter vehicles have improved mileage so they consume less fuel and generally emit fewer emissions. High-strength, lightweight thermoplastics can be used to replace metal components with virtually no difference in strength or dependability.
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The Top 6 Industrial Applications for Injection Molding
For most industries, it only makes sense to find the lowest cost yet most durable materials to produce the products they need. As a versatile manufacturing technique, injection molding plays a crucial role in developing and creating many modern products, from consumer toys to airplane components. This article will look at the top 6 industrial applications for injection molding and how manufacturers can improve existing systems
Food and Beverage
When it comes to injection molding, the food and beverage industry relies heavily on plastic materials to create product packaging and containers. Since this industry must adhere to strict sanitization and safety regulations, plastic injection molding is an obvious fit to ensure various specifications are achieved, including BPA-free, FDA-certified, non-toxic and GMA safe regulations. From components as small as bottle caps to the trays used in TV dinners, injection molding provides a one-stop-shop for all the food and beverage industry's packaging and container needs.
Electronics
Although many people see electronic components as a predominately metal piece of machinery that uses electricity to function, enhancing system longevity with corrosion-resistant plastic housings improves overall performance. As you may have guessed, manufacturing housings through the plastic injection molding processes is preferred. The computer mouse you may be using right now, to the television in your living room, likely have some components created using plastic injection molding.
Automotive Parts
Many of the parts found on modern automobiles require a broad range of intricately designed features to function correctly. For this reason, many of the leaders of the automotive industry have turned to plastic injection molding to develop, plan, and manufacture the parts they need. Typical injected molded elements include bumpers, dashboards, and smaller pieces, such as cup holders and mirror housings.
Household Products
With just a simple trip to your kitchen, there is a good chance that you will find an injection molded product or part. From Tupperware to building materials used in the construction, there is no denying that this industry would not be where it is today without injection molding. Like other industries, household products can be made more affordable by investing in large production runs for shipping to retail locations worldwide.
Agriculture
Historically, it was typical for the agriculture industry to invest in metal-made components simply because they provided a durable solution. Now, reinforced plastic options have gained favor due to new plastic material characteristics like UV-resistance, impact-resistance, humidity resistance, and much more. The ability to create durable agriculture products that stand up to the elements on a farm makes plastic injection molding an obvious fit for the agriculture industry, from feeding troughs to specialized harvesting components.
Medical & Pharmaceuticals
As many medical products must be shatter-proof, non-porous, and perfect in shape, plastic injection molding is critical for medical and pharmaceutical production. As a high volume producer, the medical industry can benefit from injection molding's decreased production times and affordable production materials while still achieving high-quality medical-grade products. Medical and pharmaceutical parts created with injection molding can range from pill bottles to x-ray components.
What are the Uses of Injection Molding
Plastic injection molding is used in all industries for applications from static-dissipating electronics housings to self-lubricating parts in the oil and gas industry. Some of the most common applications include
Consumer products
Commonly utilizing inexpensive, mechanically strong plastics like PVC, this industry uses injection molding for handheld items, storage containers, and Iot containers.
Aerospace companies use products like turbine housings and blades, pump gears, and valve seats, made from engineering plastics such as PEEK and PAI, both of which can handle wide ranges of temperatures seen by aircraft.
Electronics
In this field injection molded parts include many over molded components like wire cables and connectors. Materials used commonly include static dissipation plastics like ABS and ABS blends.
Medical manufacturers use injection molding for product parts found in medical tools, light or monitor support arms, infusion pumps, EKG machines, and tomographic imaging machines. Medical companies will utilize plastics that don't absorb moisture and that can be sterilized via steam, radiation, or gas. Some plastics needed will also have clarity requirements for transparent parts. Commonly used plastics include PEEK, polycarbonate, and polystyrene, though not Nylon, as it absorbs moisture.
Energy and oil companies utilize high temperature resistant plastics with little to no moisture absorption. This includes PEEK, which is neutral with high temperature resistance, PTFE, which has high heat deflection properties. They also commonly use nylons, which are self-lubricating and can withstand a wide range of temperatures. These companies require products like insert molded valves, electrical connectors, seals, pipe protection and liners, and other parts.
Automotive
Since vehicles can end up in an array of climates and operating conditions, automotive companies will use materials with a wide range of chemical and temperature resistance. Parts, including door panels and engine components, will often be manufactured with glass-filled nylon, as the glass adds stiffness for products like bumpers. Other popular materials include PBT, PPE-PS, and polyether imide, which has high chemical resistance.
Injection molding is cost-competitive for manufacturing high volumes of identical plastic parts. Once the mold is created, and the machine is set up, parts can be produced quickly at low costs.
The recommended minimum production volume for injection molding is 500 units. At this point, economies of scale start to kick in, and the relatively high initial costs of tooling have a less prominent effect on the unit price.
The typical injection molding cycle lasts around 15 to 60 seconds, depending on the part's size and the mold's complexity. In comparison, CNC machining and 3D printing might require minutes to hours to produce the same geometry.
With injection molding, you get your parts to market faster and gain a competitive advantage with the ability to produce multiple objects simultaneously that are identical to one another within an hour.
What Materials Can You Use for Injection Molding
Over 25,000 engineered materials are compatible with injection molding, including thermoplastics, silicones, thermosets, and resins. This means there is a wide range of materials with diverse physical properties that you can select from and design your part. The possibilities are endless.
Parts produced with injection molding have excellent physical properties that can be tailored with additives, like glass fibers, or by mixing different pallets, like PC/ABS blends, to achieve a desired level of strength.
You want to ensure that you select the right materials for your design. Keep in mind the part's impact and tensile strengths, heat deflection, water absorption, and flexural modulus of elasticity.
How Does Injection Molding Work
Tooling fabrication
Once an injection molding design is finalized the first step in the manufacturing process is to mill the tooling, which is typically fabricated from steel or aluminum. In most cases, the metal block of material is placed in a CNC mill, which then carves out a negative of the final plastic part. Additional treatments like polishing or laser etching can then be applied to the tooling to achieve specific surface finishes.
Part production
The actual production of plastic parts begins by loading resin pellets into a barrel. The temperature of the barrel is raised until the resin pellets reach a molten state and are then compressed. Next, the molten plastic is injected into the metal tool through a runner system, which then feed into the mold cavity through gates. The part then cools down, solidifies, and is ejected from the tool with ejector pins.
Types of Injection Molding
The term injection molding encompasses a handful of processes that inject liquid resin into a tool to form plastic parts. Here are four common types
Insert Molding
Insert molding is process that begins with an insert component placed into the mold before resin enters. The material is then injected and flows around the insert, typically metal, to form the final part. This is frequently used for parts that require metal threads.
Overmolding
Overmolding is a process used to manufacturing plastic parts with two or more materials. You'll often find this on parts to improve grip by adding rubber to the handle.
Liquid silicone rubber molding
Liquid silicone rubber uses thermoset materials and a chemical reaction creates the plastic part.
Thermoplastic injection molding
Thermoplastic injection molding is the most common type of molding. It injects thermoplastic resin into the mold where the material cools to form the final part.
Basic Design Principles for Injection Molding
Tolerances
With our injection molding process, we can hold about ±0.003 in. machining accuracy. Shrink tolerance depends mainly on part design and resin choice. It varies from 0.002 in./in. for stable resins like ABS and polycarbonate to 0.025 in./in. for unstable resins like TPE.
Wall Thickness
Wall thickness is important because it can lead to defects such as sink and warp. It is best practice to maintain a uniform thickness throughout an injection-molded part. We recommend walls to be no less than 40 to 60 percent of adjacent wall thickness, and all should fit within recommended thickness ranges for the selected resin.
Core Geometry
Core out parts to eliminate thick walls. You get the same functionality in a good molded part. Unnecessary thickness can alter part dimensions, reduce strength, and necessitate post-process machining.
Draft
Applying draft to molded parts is critical to ensure parts do not warp during the cool down process and it helps the part easily eject from the mold. Applying 1 to 2 degrees works well in most scenarios. If there are vertical faces, we advise incorporating .5 degrees of draft.
Side Actions
A portion of the mold that is pushed into place as the mold closes, using a cam-actuated slide. Typically, side-actions are used to resolve an undercut, or sometimes to allow an undrafted outside wall. As the mold opens, the side action pulls away from the part, allowing the part to be ejected. Also called a “cam.”
Undercuts
A portion of the part that shadows another portion of the part, creating an interlock between the part and one or both of the mold halves. An example is a hole perpendicular to the mold opening direction bored into the side of a part. An undercut prevents the part from being ejected, or the mold from opening, or both.
Bosses
A raised stud feature that is used to engage fasteners or support features of other parts passing through them. There can be a tendency to design thick bosses which will increase the likelihood of sink and voids in a part. Consider reinforcing bosses with ribs or gussets for extra strength
Gates
A gate is an opening in the injection mold tool that allows resin to enter and fill the cavity. There are three common types of injection molding gates.
Tab gates are the most common type of gate since it works well with additives and is the most cost effective option.
Hot Tip gate is best for parts that cosmetic appearance is a priority. These gates can also reduce wear on tooling and flash.
Pin, Post, or Tunnel gates are ideal for cosmetic parts that don't require a vestige. Sometimes not an option depending on material and geometry.
Ribs
A rib is a thin, wall-like feature parallel to the mold opening direction, its used to add strength and support to features like bosses and walls. To prevent sink, ribs should be no more than 60% of the wall's thickness.
Ejector Pins
Ejector pins are installed in the B-side of the mold and help to release the plastic part from the tool after the part has cooled sufficiently. Designing in sufficient draft can help reduce the need for ejector pins on a part.
Logos and Text
Sans serif fonts will be the easiest to mill into a mold with text. We recommend font larger than 20 pt. and no deeper than 0.010 in to 0.015 in.
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Our factory
Founded in 2019, Alec Model is located in Bao 'an District of Shenzhen, close to both Shenzhen Airport and Hong Kong Airport, covering an area of more than 2,600 square meters. There are 6 manufacturing zones including CNC machining zone, sheet metal making zone, manual work zone, polishing and finishing zone, quality management zone, engineering and project management zone, which can meet the production needs of various precision parts
FAQ
Q: What is the injection molding process?
Q: Why is injection molding so popular?
Q: How long does injection molding last?
Q: Why is injection molding so expensive?
Q: Can you do injection moulding at home?
Q: What industry uses injection molding?
Q: Is injection molding the same as roto molding?
Q: How long does it take to injection moulding?
Q: What are the 4 stages of injection molding?
Q: Does injection moulding use a lot of energy?
Q: What is the hardest plastic for injection molding?
Polycarbonate (PC): Polycarbonate is a transparent thermoplastic that offers some of the strongest, most shatter-resistant construction available for plastic injection molded products.
Q: What is the best metal for injection molding?
If your injection molding project requires tight tolerances and high volumes, S-7 is the pre-hardened tool steel of choice. There are few, if any, downsides to S-7, and the upsides are considerable: Stability during heat treating, and resistance to softening at high temperatures.
Q: What is the opposite of injection molding?
Q: Why is injection molding so popular?
Q: Can injection molding make hollow parts?
By its very nature, injection molding cannot be used to make hollow objects. One option to get around this limitation is to make your part in two different pieces and connect them later. This is a pretty popular option… keyboards, TV remotes, and my Otterbox case are all made this way.
Q: How thick can you injection mold?
Q: Who needs plastic injection molding?
Their resistance to the elements makes injection molding products ideal for agricultural tools like feeding troughs and stable ground grids. Their lightweight durability makes them a suitable choice for tractor components, cooking utensils, or brewing machinery.
Q: What is an example of injection molding in the real world?
Q: Is PVC used for injection molding?
Q: Is injection moulding easy?
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