What is 2K injection moulding? | Reobijn

2K injection molding is a production process in which two materials (colors) are processed in one plastic part. This plastic molding technology combines two materials or two different color materials into one ending plastic part using a 2K injection molding machine.

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The chemical bonding process involved in this happens because they are capable of joining two or more materials into one part. When using a 2K injection molding technology process, the choice of material will be the most important factor for the project&#;s success. Two completely opposite polymers can be used for a ready-to-use product.

The 2K injection molding process is mainly used for products that have to meet several special function or appearance requirements. For example, some products must be waterproof, drop-resistant, and dust-proof. Other products must have a variety of colors on the surface to meet aesthetic requirements. Some products may also require a good grip and touch. This includes realizing effects such as a soft-touch surface, an ergonomic design, a two-tone appearance, watertightness of a product, shock absorption, moisture resistance or making plastic parts anti-slip.

An example of a product is the cap of a swing-top bottle made of PP with a TPE seal.

Advantages of 2K injection molding:

• High precision and stable quality
• Good structural strength and long service life
• Good appearance
• It lowers production costs and increases the value of composite products

The choice of material is very important, as different plastics have different physical properties. The plastics that are processed together must be compatible with each other and the difference in shrinkage of the two plastics should be small.

A disadvantage of 2K injection molding is that the costs for a mold are higher than a mold for 1K injection molding. Furthermore, the injection molding machine must be equipped with a second plastic component, which also makes the machine more expensive. Ultimately, with 2K injection molding, the costs are recovered by reducing labor and assembly costs, because the manual application of, for example, a seal is no longer necessary. This avoids an assembly step.

Another disadvantage of 2K injection molding is that it makes the recycling of the plastic products difficult, because often two different plastics are combined. Even when the plastics are &#;from the same family&#;, the quality of return flows will be less. This makes it difficult to reuse the plastics for a high-quality application.

In addition to 2-component injection molding, it is also possible to process three types of plastic into one plastic part. This is called 3K injection molding.

What is overmolding (over mold)?

Overmolding or over mold is an operation in which two or more mediums (substances) are merged to form an end-molded product. Plastic overmolding needs to make two separate molds: one is the substrate (the first mold), and the second mold is called the overmold (usually a TPE material for the second mold). If the substrate is metal or brass, this type of overmolding is normally called insert molding, and insert molding only needs one mold to finish the process.

The plastic overmolded materials most commonly used are thermoplastics (TPE) and rubber, or the same material but different colors. During overmolding, the activity that happens is either mechanical or chemical, which leaves the two substances bonded.

The overmolding process involves producing the molded part (substrate) from the first mold and moving it to another related over mold. The substance can be used to combine the surface molded with the molding substrate. Otherwise, the molded material can be put back on the surface from which it was extracted, and the overmolded substance can be added. Types of over molding include two-shot sequential over molding, insert over molding, and multi-shot injection molding.

In two-shot sequential plastic injection overmolding, the molding machine injects the first plastic resin into the first mold cavity (both molds in one machine), then moves the first molded part to the second overmold immediately, closes the mold, and injects the second material (in the meant time injecting the first shot as well), using the first component as an insert for the second shot using a different material or color. This process requires a special injection machine with two injection units.

Insert over-molding uses a pre-molded insert placed into the mold before injecting the second material; if the inserts are metal or brass, then we call it metal insert molding. This over-molding process, which we used a lot, for example, metal cwrew insert molding, filter insert molding, this type of over moldings use traditional injection molding machine to proceed, which put the metal inserts into the mold cavity during the single injection molding cycle.

Overmolding cost

The base cost of an overmolding is not a fixed number that will be the same for every application. It has a varying value that can fall between 1 and 10 dollars.

This is an extremely wide price bracket. The right value changes based on several components involved in the overmolding process. These factors that influence the cost are:

Injection molding Equipment

The upfront cost of equipment for injection molding can change greatly depending on its application and type.

There is little-scale injection molding equipment that businesses keep in house. Then there are big overmolding machines generally used by service providers and those in the big-scale manufacturing industry with large production volumes.

Professional industrial overmolding equipment costs between $50,000 and $200,000. There may be shipping costs involved. These machines are not for amateurs and hobbyists, as they need skilled operators.

Over-mold manufacturing costs

While the overmolding equipment is a one-time investment, creating the over mold according to each custom design is an additional cost, and each single unique overmold part design will require a unique over mold. It is an expense for every different part produced. So, over mold manufacturing costs are one of the most vital driving factors for overmolded parts.

This over mold cost can vary depending on the part design, part size, and quality required to create the molds. Generally, three factors are employed for this objective, which are listed below:?

Design complexity

Highly complex designs with more cavities and top mold polish result in extra costs. Such designs need development, research, and technical skill. For this objective, you can hire a professional for the design process. Both options incur expenses.

Part size

Over mold is the same as other injection molds; a large size will require a large moldbase and molding machine, which will increase the over mold cost and unit over moled part cost.

Labor costs

Most steps involved in overmolding are automated and run by software systems. For example, CNC machines are run by computer numerically controlled programs; 3D printers run on their own programs; and injection molding also has mechanical processing.

Final summarize for the overmolding cost

If you are looking for overmolded parts or over mold for your custom injection molding parts, then you do not need to pay any cost on the injection molding equipment, because your over molding supplier should have this, but you need to pay for the over mold cost, overmolding process cost, materials cost, packing cost, and so on. If you want to know the price of your overmolding project, please contact us and we will quote you in 24 hours.

How to reduce overmolding cost

Overmolding is the preferred manufacturing process due to its cost-effectiveness and reliability.

While the process is affordable compared to its alternatives, you can further decrease the costs. For that objective, here are some pointers that you need to take into account:

Optimizing the CAD design

A single part can be approached via different CAD designs. Anyway, not every design idea is perfect. Some designs for the same part may lead to time and resource waste. So, simplifying part complexity via efficient CAD design ensures optimal utilization of resources.

Reducing part size

Bigger parts are not always excellent parts. When the size of the parts rises, so does the expense of the injection molds needed for the parts. If the same process can be accomplished by decreasing the part size, it is a good idea to opt for it.

Contact us to discuss your requirements of 2k injection moulding. Our experienced sales team can help you identify the options that best suit your needs.

Resuing over molds

Make full use of the over molds by reusing them for many applications. You cannot just use the same mold for the same part but also for similar parts as well. This can be performed by making adjustments or molding wherever possible.

Using DFM analysis

DFM stands for design for manufacturing. DFM in overmolding refers to producing a part that serves the objective of the customer and is within their stipulated budget.

For DFM, analysts consider many factors based on science, art, and technology to find the most successful design, resulting in reducing injection over mold costs. Go to design for manufacturing page to know more.

Advantages of injection over molding

1. Compared to 2K injection molding, over molding is easier to make. You can use a normal injection molding machine to make two or three different colors in one molded part or two or three different materials in one end part.
2. For some small quantities of two-color molding part projects, you do not need to invert or hire a 2K injection molding machine; using the overmolded process is the best and most cost-effective way to meet customer requirements.
3. It increases the design diversity and also exalts the end product in many material compositions.
4. With reduced assembly costs, there are fewer secondary activities or processes carried out on the end products. This reduces the cost of labor. Also, after manufacture, no more costs are incurred.
5. The parts have a high level of stability and constitution since, after being left to mechanically interlock, they become one.
6. Products overmolded using plastic have high resistance to vibration and shock due to the plastic resins having been structured perfectly.
7. The plastic molding parts are more reliable because there is no bonding at the production stage.
8. The end items are of the desired standard, such as eye-catching designs and firm components.

Disadvantage of injection over moulding

1. Since the over molding process involves moving the first molded substrate part to another over mold, the tolerance is not as good as in the 2K injection molding process.
2. The production capacity is not as efficient as 2K injection molding, as it requires robots or manual labor to insert the substrate into the overmolded mold. This will take time, and the molding parameter is sometimes not stable, especially when two or more substrates are in one mold. This will lead to additional problems and a higher waste rate, resulting in twice the amount of waste (from the substrate and overmolded material).
3. With the overmolding process, there are fewer available choices in terms of plastic compatibility. Some materials may not bond well together or may not be able to withstand the high temperatures and pressures of the injection molding process.
4. There are no secondary practices carried out on the end products of overmolding. When the molding material becomes cold, activities and adjustments come to a complete halt.
5. In cases where products are scarce, it is expensive to run such an operation. Sincerely, you need someone to put the substrate into over mold, so the cycle time and production cost are increased accordingly.
6. The overmolding process normally requires two molds, one for substrate and one for overmold, so the initial mold cost will be higher.
7. Overmolding is a more complex process than traditional injection molding, requiring precise coordination between the two injection systems and a proper mold design.
8. If there is an issue with the overmolding process, troubleshooting and fixing problems with overmolding can be more difficult than with traditional injection molding.

What is 2k injection molding? (Two-shot molding)

Two-shot injection molding, or 2K injection molding, is a manufacturing process used to mold two colors or materials into one plastic. This two-shot molding technology blends two materials or two different material colors into one plastic part by using a 2K injection molding machine.

The chemical bonding process involved in this process is very important because it is capable of combining two or more materials into one part. When using the 2K injection molding technology process, material selection will be an important factor in the success of the project or not.

Benefits of 2K injection molding 

2K injection molding provides a number of benefits over traditional one-material injection molding. Some of these benefits contain:

Cost-effective

The 2-step process needs just one machine cycle, rotating the primary mold out of the way and putting the secondary mold around the item so that the second, compatible thermoplastic can be inserted in the second mold. Because the method uses only one cycle instead of separate machine cycles, it costs less for any production run and needs fewer employees to make the end product while delivering more items per run. It also ensures a powerful bond between the materials without the need for additional assembly down the line.

Improved efficiency

Two-shot molding permits multiple components to be molded with one tool, decreasing the amount of labor required to run your parts and eliminating the need to join or weld components after the molding process.

Better quality

Two-shot is carried out within one tool, permitting lower tolerances than other molding processes, a high level of accuracy and repeatability, and reduced scrap rates.

Complex molding

Two-shot molding permits the creation of complex mold designs that incorporate different materials for functionality that cannot be achieved via after-molding processes.

Disadvantages of 2K injection molding

2K injection molding has many advantages, but like everything, it has its pros and cons.

A disadvantage of 2K injection molding is that the mold costs are higher than traditional injection mold. because 2K injection molding requires two molds, the first shot and the second shot (that is why we call it two-shot molding), and making 2K injection molds are more difficult than making two separate traditional molds because those two molds will run together in the same machine (a two-shot injection molding machine). so it needs two molds to switch over without any problem.

Additionally, the 2K injection molding process must use a 2K injection molding machine, which also makes the machine more costly and requires a special technical operator to adjust the machine. This is also a higher cost than traditional injection molding. Ultimately, we recover the 2K injection molding costs by reducing labor and assembly costs, as the manual application of, for example, a seal is no longer necessary. This eliminates an assembly step.

Another disadvantage of 2K injection molding is that it makes the recycling of plastic items difficult because often two different plastics are gathered. Even when the plastics are &#;from the same family,&#; the quality of return flows will be very low, which makes it hard to reuse the plastic for a high-standard application.

Conclusion

You may have questions about when you need to use over molding and when you should use the 2K injection molding process. Here are some simple suggestions:

1. If the quantity is not so high, maybe only a few thousand or ten thousand, then use the overmolded process; this will save you some mold costs.
2. If you need over a half million parts, then 2K injection molding is the best molding process to save money for you.
3. Some of the parts can only be overmolded, and others can be done by the double injection molding process only. This depends on the part structure. If you are not sure about this, you are welcome to send your data to

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   . We can check this for you and offer you a price for your reference.

Looking for over molding or 2k injection molding service?

Sincere Tech is one of the best injection molding companies in China. Send us your 3D design drawing and your requirements; we will never share your data with anyone else. We are willing to sign an NDA document to ensure the safety of your project.

We will offer you the most competitive price for high-quality overmolded parts, 2K mold and molding, plastic tooling, and plastic parts for the long-term business relationship, and we will suggest the best injection molding process for your products.

More than 18 years of experience providing plastic mold making and custom mold services in overmolding, 2K molding, die casting, machining, and so on, plus 18 years of fluent technical English communication (technical English communication is very important to work with worldwide customers).

Small orders are accepted. Main export markets: Asia, Australasia, Central and South America, Eastern Europe, North America, and Western Europe.

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