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Overmolding Design Success: Strategic Considerations for Company Prototype Designs

Posted on May 20, 2024 by faz_business

Today’s post covers overmolding design success tips for designing company prototypes. Can you quickly tell the quality of a pair of pliers by just looking at it? Will the battery pack of a drill drain fast after you pull the trigger? Can you determine a product’s overall integrity based on its appearance or how it feels in your hands? Believe it or not, you’re not the only one who doubts some products before you touch or use them. Even the most minor design details can provide insight into the material’s sturdiness and the quality of the engineering design services and applications used.

Before a product comes to fruition, companies create several prototype designs, where overmolding enters the picture. Overmolding is a feature that can take the appearance and feel of a product to the next level. It enhances aesthetics, performance, and functionality, making it more popular and in demand among manufacturing prototype design firms for portable devices, medical devices, and consumer products. Continue reading to know more about the strategic considerations to ensure a successful overmolding design:

What is overmolding?

Overmolding refers to the process of making one part using the combination of two or several different materials. The first material, the substrate, is often fully or partially covered by overmold or subsequent materials throughout the manufacturing process. The substrate can be anything, including a molded plastic part, a machined metal part, or even existing products such as electrical connectors, screws, or threaded inserts. This first piece will soon transform into one continuous part of often mechanically interlocked and chemically bonded materials of different types.

Overmold materials, usually plastic, begin in pellet form. The design for additive manufacturing company combines the pellets with additives such as foaming agents, colorants, and other fillers. These are heated afterward to their melting point before they’re injected in liquid form into the mold tooling. There are several limitations on the types of materials suitable for use for overmolding. If you’re overmolding a metal part with plastic, any plastic can be used. There might be compatibility issues if you’re overmolding a plastic part with a different type of plastic, TPE, or rubber.

The material manufacturer often releases compatibility charts for overmolding. As a unique process of custom injection molding and casting services, overmolding leads to the seamless mixture of several materials into one product or part. It often involves a plastic-base and rigid component overload with rubber-like, pliable, and thin TPE or thermoplastic elastomer exterior layer or other types of materials with the use of either two-shot or multiple-shot molding method or a single-shot or insert molding. After considering its benefits, plastic overmolding may be ideal for your company’s projects.

Common uses and applications of overloading

Overmolding is used for different reasons that may vary based on the specifics of a particular project. Some of the common materials where the process is used include personal care items and tool handgrips. Below are several typical applications of overmolding:

Plastic over plastic

Molding a rigid plastic substrate is the first step. Another rigid plastic will be molded around or onto the substrate. These plastics may differ in resin or color.

Rubber over plastic

A rigid plastic substrate is molded first. TPE or soft rubber is molded around or onto the substrate. It typically creates a soft grip spot on a tricky area.

Plastic over metal

A metal substrate is formed, cast, or machined. The substrate will be inserted into the injection molding tool. The plastic is molded around or onto the metal. It is usually used for capturing metal components in the plastic part.

Rubber over metal

A metal substrate is cast, formed, or machined. The substrate will be inserted into the injection molding tool. The TPE or rubber will be molded around or onto the metal. It is usually used to create a soft grip surface. However, there are compatibility issues and limitations when using different materials. It also doesn’t mean that you can only use two materials. It’s common for 3D product modeling companies to design products where one part uses three materials to achieve grip surfaces and color breaks.

The overmolding process

The substrate part or material is typically placed into the injection molding tool. The overmold material is then shot around, onto, or into the substrate. Once the overmold material solidifies or cures, the two materials will be combined to form a single part. It is often a good idea for the mold material and substrate to interlock in a particular mechanical capacity. It will help ensure the two materials are physically held together and not just chemically bonded.

Strategic considerations before overmolding design

Although the overmolding process is cost-effective and can offer outstanding adhesion between the materials, proper planning is required to ensure its success. The machinist, for example, should choose suitable materials to achieve optimum adhesion and carry out the function of the part. It is one of the main reasons why the machinist should have proper planning of the overmolding design guide.

Since the design is often complex, you must be extra careful when developing the overmold design.
Consider the following elements that contribute to the success of the design, ensuring its effective realization.

The function of the part

A complete understanding of the part’s intended function plays a significant role in successfully designing an overmolding part. For this to be possible, you must ask several questions about the part.

1. What is the proposed objective or purpose of the part?

The design process must first understand the purpose of designing the part. Since overmolding has several uses and applications, knowing the goal of the product is essential to determine the suitable process to use. If you’re planning to have a seal molded on a water-resistant case, the goal of the product is a waterproof seal.

2. What kind of exposure will the part endure and deal with?

You also need to consider the kind and amount of exposure the product will be dealing with when it’s in the line of duty before you develop a design. If the part endures harsh radiation such as UV light, this type of product can use certain plastics.

3. Why do you want to mold the part over?

The main reason why you plan to use overmolding for the part can help you determine the complexity of the design. If you hire an injection mold designer to develop a TPE overmolding design guide for rubber-like or TPE to be cast on a product handle, the proposed gadget could be for grip, comfort, ergonomics, or vibration absorption. A satisfactory answer to this question will help you determine the most appropriate material and map out a correct overmolding design guide.

4. Will the part receive a large-scale production?

If the part is planned for large-scale production, you must consider it when developing your overmolding design guide. For example, an overmolding part intended for vibration dampening will feature a thick wall that will require a longer cycle time and more materials to produce each part. Making this kind of product can get quite costly, although it might be worth the investment if you only need several pieces.

Scenario

Once you have confirmed that the function of the part will fit in with the design, your next step for the 3D design services is to evaluate the instances where it will be used and their effect on the physical features. The following are the four most common scenarios where overmolding products are used:

1. Grip addition to a substrate

Different products, including kitchen utensils, garden hoses, and drills, require a certain amount and level of grip that allows users to control the product even under wet conditions. In cases like this, the most recommended way to add grip to such products is to cast rubber-like plastic over the handles. This process only needs a little material and may only need production in low quantities more often than not.

2. Comfort

When the grip is added to a substrate, this also acts as a source of comfort every time the product is used. The scenario is the same as the first point in most cases. The rubber grips used on bicycle handles are the perfect example of products that combine the two scenarios.

3. Sealing

This scenario requires longer cycle times and more materials to make an overwhelming product. These seals often feature water-resistant properties and must achieve optimum substrate adhesion. Before you design this type of part, looking for the material that will create the maximum adhesion with the substrate and offer the highest form of waterproof abilities is essential.

4. Vibration dampening

This specific type of usage not only has the longest cycle time but also needs the most amounts of materials. The TPE part that will be produced must have an adequate thickness for absorbing the vibrations of the substrate you plan to cast it on. This scenario is applied to most high-energy machines, such as drills and pumps.

How Cad Crowd can help with overmolding design

Contact Cad Crowd to help you find the best overmolding experts to help you with the following prototype designs for your company. Get a free quote now.

Understanding Injection Molding, Insert Molding, and Overmolding for Companies

Posted on May 18, 2024 by faz_business

Have you ever wondered why most tools are easy to hold and grip? It’s all thanks to the introduction of processes, including injection molding and casting services, insert molding and overmolding. However, if you’re not part of the industry or haven’t heard of these terms, they can be confusing. It’s understandable because insert molding and overmolding are two types of injection molding. Continue reading below to learn more about injection molding, insert molding and overmolding processes.

What is injection molding?

Molten plastic is injected into a mold during injection molding. The mold will then cool down, and the plastic will become solid. Companies use injection molding to produce various products, such as consumer goods, automotive parts, and medical devices.

How does injection molding work?

A popular technique used by manufacturing design firms, injection molding is used to create parts by injecting molten materials into molds. This is a relatively common process for plastics, although it applies to glass, ceramics, and metals.During this process, the mold of the product is made first. A mold is a hollowed-out block that will give shape to the liquid or molten material. The mold will then be placed on the injection molding machine.

The plastic pellets will be heated until they melt. This molten plastic will go under high pressure into the mold. While the material hardens as it cools, it will take on the mold cavity’s shape. Once the plastic cools down and solidifies, the product or part will be ejected from the mold. Injection molding allows the creation of parts of all sizes and shapes. Molds can also be designed to produce more complex internal features. This ability to develop intricate designs is why injection molding is applicable in different industries.

What is insert molding?

The manufacturing process of insert molding involves adding parts, mainly metal, on top of the molded parts. Insert molding consists of the use of inserts in the injection molding process. This process is done before the product is cured and helps cut down the processes required during assembly following molding. After the parts that will be molded on top of the product are obtained, another layer will be accepted after the parts are inserted into the mold.

Insert molding can be carried out in two ways: automated and manual. Manual insert molding is relatively cheaper than automatic insert molding. But as far as consistency is concerned, automated insert molding is the ideal choice. It reduces human errors and increases efficiency. Introducing inserts onto the mold cores cast using the automated or manual process will result in plasticizing the plastic pellets after the mold halves are closed.

The pieces will be ejected from the mold after the plastic hardens. The inserts will then be encapsulated in the parts. An excellent example of insert molding is the addition of a plastic layer over the screwdriver’s metal part for the plastic handle to be produced.

What is overmolding?

Overmolding is a manufacturing process involving a seamless combination of different materials into a single item or part. The overmolding process involves two essential steps. Molding and curing the substrate, typically plastic, is the first step. This is followed by direct molding the layer over the initial layer to produce a single product. Product design companies designing a toothbrush is a typical example of overmolding, where a basal layer is formed first, followed by a rubber layer.

Overmolding can significantly reduce production costs. Some of the critical components of the process include the rigid plastic base covered by a flexible, thin, rubber-like material. This manufacturing process has astounding versatility as it is helpful for different home items, including toothbrushes, hand tools, and razors.

Advantages of injection molding

1. High and efficient production

After the molds are developed, it speeds up the process, with cycle times only requiring 10 seconds. This ideal option for high- and medium-volume production runs from 10,000 parts to more than 100,000, depending on the molds used.

2. Intricate detail

High-pressure injection forces molten plastic into the mold, enabling the creation of intricate and detailed shapes.

3. More choices of materials

Choose from a diverse array of plastic materials tailored to meet the specific properties required for the final part.

4. Minimal to no post-production

Little to no post-production is required since the parts often have pleasing aesthetics.

5. Lower cost per part

The cost per part is meager for high-output production runs.

6. Reduced waste

Unlike most manufacturing methods, very little waste is produced during molding.

7. Repeatability

Identical products can be manufactured repeatedly. It’s a good choice for parts with high reliability and tolerances across high volumes.

Disadvantages of injection molding

1. Design limitations

There are several design elements a product designer need to consider during injection molding. These include controlling the thickness of the wall, preventing sharp edges and undercuts, and using radii and drafts to eject the parts.

2. High initial cost

A substantial capital cost might be required for higher volumes of production that require a great deal of machining and time to produce.

3. Longer initial lead times

Some tools may take several weeks to be produced, so consider using other technologies like CNC machining services or 3D printing, especially for lower production runs.

4. Not cost-effective for small production runs

Injection molding might be unsuitable for smaller production runs when other manufacturing processes are more suitable.

Advantages of insert molding

1. Lower cost

Insert molding makes it possible to create thousands of parts of products in just one day. Its economic significance leads to reduced costs for the entire molding production process.

2. Faster assembly time

The assembly of products needed in CNC machining is often challenging. However, insert molding can do away with the need for assembly. The overall production cost is reduced because no assembly time is involved.

3. Multipurpose parts

The parts produced by 3D modeling design services for machine parts using insert molding can serve various purposes depending on the specific function that the product is intended to serve. The combination of metal and plastic parts will benefit not only the end users of the product but even the manufacturers. The use of plastic parts can also improve the design’s flexibility and make it lighter than metal.

Disadvantages of insert molding

1. Multiple technologies for manufacturing

Machining processes such as die casting are required for custom-designed inserts. This is made before the start of the actual process of insert molding. This results in a higher cost per part.

2. The complexity of part design

The injection molding designers must be familiar with the design of the technology’s manufacturing principles for them to produce custom-made metal inserts in insert molding. This is the only time when it becomes practical to integrate the involved technologies.

Advantages of overmolding

1. Eliminate the need for adhesives

Adhesives are no longer required in overmolding since the different parts get the chance to fuse during the process. This will increase the durability of the parts or products produced. It also results in an overall reduction in production costs.

2. Better product performance

Adding other suitable quality materials to a product can significantly improve its performance. Those products that go through overmolding have two edges in terms of materials over the traditional products used in most industries. This will, therefore, enhance the performance of the products made using overmolding.

3. Improved flexibility of materials

Combining several parts is required in overmolding, increasing the part’s flexibility because it leverages each of the benefits of the involved materials. Design for manufacturing and assembly firms can also use an overmolding design guide to enhance flexibility further.

Disadvantages of overmolding

1. De-bonding

The risk of delamination may occur if two different parts are bonded together in an injection mold. Delamination may take place if there is a change in the range of optimal temperatures. Mechanical interlocks will be required when the available heat fails to bond the two materials successfully.

2. Multiple processes of production

Two steps are involved during manufacturing using overmolding, which can increase the cycle time of each part. The production cost may also be higher than just molding one part in one process. Overmolding also needs more tools compared to single molding because the process involves two steps.

How Cad Crowd can help

Injection molding and its two specific types, insert molding and overmolding, are efficient and helpful processes. These techniques help produce different parts with various uses and applications. Before embarking on your project, it’s vital to assess these methods to make a well-informed decision. Knowing what type of finished part you plan to make and its specific application will help you identify the proper process. Cad Crowd offers injection molding and casting services and can help you find specialists to guide you through every step to ensure successful production. Contact us for a free quote.