Magnet Overmolding Advantages Applications and Process Considerations
2024-11-18
Magnet overmolding refers to encasing magnets in plastic through injection molding. In this process, a magnet is placed in a
Our Manufacturing Process
- Injection Molding
- Overmolding & Insert Molding
- Compression Molding
- Urethane Cast Molding
Injection Molding
What is injection molding? How does it work, and what are the basic elements of it?
In this section, you will have a clear understanding of these questions, learn common examples of injection molded parts, and get insights into the fundamental principles of injection molding.
Table of Contents
What Is Injection Molding
Injection molding is a manufacturing process that allows for identical items to be produced in large volumes with good tolerances. This method involves injecting molten material into a mold, where it cools and solidifies. The materials used in injection molding can range from metals and glasses to elastomers and even confections. The most common materials are thermoplastic and thermosetting polymers, which can be colored or mixed with additives.
Once a product is designed, typically by an industrial designer or an engineer, molds are created by a toolmaker from materials like steel or aluminum. These molds are precisely machined to form the desired part features. Injection molding is capable of producing a wide range of parts, from small components like buttons to entire car body panels. In fact, nearly every plastic part around you, whether in consumer goods or industrial appliances, is manufactured through injection molding.
Injection molding is particularly popular for on-demand manufacturing due to its low per-unit cost for high-volume production and the ability to create flexible customizable parts with repeatability. However, some projects may face restrictions, such as high initial investments and relatively longer turnaround times, typically at leatst four weeks.
Injection Molding History
Injection molding has evolved with time significantly. It all started in 1846 when the British inventor Charles Hancock first patented an injection molding machine. This was followed by American inventors John Wesley Hyatt and Isaiah patenting one of the first machines in 1875. Although the machines could only mold buttons, combs, and similar, it still marked the beginning of the injection molding manufacturing industry.
During World War II, the demand for cost-effective and large-scale produced products boosted the industry. In 1946, American inventor James Watson Hendry invented the first screw injection machine, which solved the issues with uneven heating of the plastic and enabled the production of colored parts. Even today, screw injection machines account for the vast majority of all injection machines.
In today’s society, injection molding is applied in numerous industries and developed to a $300 billion market size. Growing demand for plastic parts in various industries such as automotive, packaging, home appliances, electronics, and medical equipment has driven the injection molding industry.
Injection Molding Process
Once the mold is finished, the injection mold machines can repeat the injection cycle millions of times to produce identical products. The main process of injection molding is divided into the following 6 steps.
- Clamping: In the clamping stage, the two halves of the mold are securely closed, ensuring it remains tightly sealed during injection to prevent material leakage.
- Injection: During the injection phase, molten material is forced into the closed mold under high pressure, filling the cavities to create the product.
- Dwelling: Dwelling involves maintaining pressure on the mold to allow the material to cool and set within the mold, ensuring the part takes its final shape.
- Cooling: In the cooling stage, the mold with the injected material is left to cool, allowing the product to harden and become suitable for ejection.
- Mold Opening: After cooling, the mold is opened, separating its two halves, and revealing the formed product within.
- Removal of Products: The finished product is ejected from the mold using an ejector system, such as pins or a plate, and is then ready for inspection and further processing.
Injection Molding Machine
An injection molding machine, also known as an injection press, is the equipment used to manufacture plastic products in the injection molding process. It consists of two main components: the injection unit and the clamping unit. The main function of the clamping unit is to open and close the mold and eject the product. The function of the injection unit is to melt the plastic by heating it and then inject the melted plastic into the mold.
Presses are graded according to tonnage, which indicates the clamping force that can be applied to keep the mold closed during the injection molding process. Tonnage ranges from under 5 tons to over 9,000 tons, with higher tonnage machines rarely used in production operations.
Injection molding machines are classified by their drive system, with typical types including hydraulic, mechanical, electric and hybrid injection molding machines. Often a robotic arm is used to remove the molded part, but more commonly the part is dropped from the mold through a chute into a container.
Injection Mold
A mold or die is a tool for making plastic parts. It is a hollow metal block into which molten plastic is injected to form a certain fixed shape. The molten plastic flows into the mold through a gate and fills the mold cavity through runners and sprues. The mold then opens after the cooling process and the ejector rod of the injection molding machine pushes the ejector plate of the mold to further eject the molded part.
Due to the high cost of manufacturing, molds are often used for mass production of thousands or more parts. Typically, molds are made of hardened steel, pre-hardened steel and aluminum. When considering mold materials, the primary considerations are cost and the life cycle of the molded product. Molds can be made by CNC machining or electrical dischrage machining processes.
Molding
Molding is a system consisting of gates, runners, gates and final products. Sprue refers to a passage through which the resin flows into the mold. A runner is a channel that introduces molten resin into the mold cavity. A gate is a small opening in each cavity that allows molten resin to enter.
Molds are usually designed with multiple cavities connected by runners so that multiple parts can be manufactured at one shot. In this case, if the length of the runner to each cavity is different, the cavities may not be filled at the same time, so the size, appearance, or performance of the parts will often be different for each cavity. Therefore, the runner is usually designed so that the gate length is the same for each cavity.
Sprue and gate marks are often found on the final parts, those features are not desired but unavoidable due to the nature of the process. Skilled part and mold designer place these aesthetic detriments in hidden areas if feasible.
Different Types Of Injection Molding Process
While most injection molding processes are traditional, there are many different variants of injection molding processes, including but not limited to the following:
- Die casting
- Metal Injection Molding
- Thin Wall Injection Molding
- Liquid Silicone Rubber (LSR) Injection Molding
- Reaction Injection Molding
- Micro Injection Molding
- Gass-assisted Injection Molding
- Cube Mold Technology
- Multi-material Injection Molding
Benefits and Limitations of Injection Molding
Like other molding methods, injection molding has its benefits and limitations. Here we will have quick rundown of the key advantages and disadvantages of injection molding, help you explore whether it is the suitable solution for your applicantion.
Benefits of Injection Molding
It is a high efficient and fast production process
Each injection molding cycle takes only 10-60 seconds, with some complex geometries taking longer. Still, injection molding is extremely fast compared to 3D printing or CNC machining, which can take minutes or even hours. The process is suitable for medium to high volume production of 10,000 to 100,000 parts. You can also use multi-cavities mold to increase production.
It allows to manufacture identical products with good repeatability and dimensional stability.
Once the mold has been developed, you can produce the identical product over and over again. This is ideal for parts that require high tolerances, high reliability, and high volume production. If the mold maker builds the mold properly and maintains it well, the mold will last a very long time and ensure a dimensionally stable product.
It can handle complex part designs with tight tolerance.
Injection molding is well suited for complex parts, accommodate parts with complex configurations featuring like tabs, ribs, metal inserts, side cores, and holes.
In most cases, injection molding can achieve tolerances of ±0.3mm, and in some cases even ±0.100mm. Such part accuracy is sufficient for most applications and is comparable to CNC machining and 3D printing.
It has low cost per part
For high output production runs the cost per part is very low. Normally, the higher production volume, the lower per unit part. Besides, other processing techniques may require multiple operations like polishing, whilst injection molding can do it all at once.
It is flexible in material and color
There is a huge of resin that you can select from depending on using condition of final parts, common resins like thermoplastics, thermoplastic rubber, checmical resistant plastics. You can use colorant to adapt to the color you like, or use fillers in the moulding materials to add greater strenght to the completed parts.
Limiations of injection molding
It has high start cost
Injection molding requires a high upfront cost, primarily the upfront cost of the mold. Molds need to be made before custom parts or products can be produced, and the molds need to be accurately designed to ensure that the final product meets quality standards, all of which can lead to high manufacturing costs, and this upfront investment can be a deterrent for projects that intend to produce small batches or prototypes.
It has long initial lead time
The long initial lead time for injection molding is due to the complexity of the mold making process. It involves meticulous stages of mold design, development and production. After the mold is made, it needs to be tested on an injection molding machine, and only when the test sample meets the quality standards can production begin. As unexpected surprises may be encountered at each stage, it is important to allow sufficient time for each injection molding project to avoid disruption to the product launch.
Small part runs are not cost effective
Injection molding is most cost-effective when producing large quantities of parts. The high initial tooling costs are distributed across a larger production volume, making each part more affordable. However, when it comes to producing small quantities or short runs of parts, the cost per unit can become prohibitively high. This is why injection molding is often more suitable for applications where mass production is anticipated.
It need careful design and design changes are expensive
The design of the part or product plays a vital role in injection molding. Parts need to be carefully designed to minimize production defects and avoid problems such as failure to molding. Additionally, it can be costly and time-consuming if design changes need to be made after the mold has been created. Making changes to the mold at this time can lead to additional expenses and potential production delays. Minimize the potential for costly design changes by designing thoroughly and accurately at the outset of a project.
Injection Molding Application
- Automotive Components: Injection molding is widely used in the automotive industry to produce a variety of components. It ensures precision and consistency in creating parts like dashboard panels, door handles, and headlight lenses.
- Consumer Electronics: The electronics industry relies on injection molding to craft cases, connectors, and intricate components for various devices. It’s instrumental in producing phone cases, cable connectors, and remote control buttons.
- Toys and Games: Injection molding is pivotal in the mass production of toys and game pieces. This process enables the cost-effective creation of popular items like action figures, board game tokens, and iconic LEGO bricks.
- Packaging Products: Injection molding is the go-to process for producing a vast array of packaging products. From bottle caps and food containers to cosmetic packaging, it provides cost-effective and efficient solutions.
- Household Goods: Injection molding plays a key role in the production of common household items. Everyday essentials such as hangers, utensils, and storage containers are made using this method.
- Industrial Equipment: Injection-molded parts are integral to the industrial sector, producing components for machinery and tools. This includes gears, machine housings, and conveyor belts.
Related Resources
Read More »
Everything You Need to Know PCB Overmolding
2024-11-18
PCB overmolding not only shields the PCB from external threats (such as moisture, temperature variations, and mechanical stress) but also
High Quality Customized Toilet Valve Rubber Sealing Gasket
2024-11-18
Toilet valve rubber sealing gaskets are important components in plumbing systems. They typically last between 5 to 10 years on
Everything About the Cable Overmolding
2024-11-18
Cable overmolding is a specialized manufacturing process that enhances the durability and functionality of electrical components by encapsulating wires and