Many beginners want to quickly understand overmolding. As an industry leader, we have involved overmolding product engineers and wrote this latest ultimate guide in 2023, which can guide everyone to quickly understand overmolding products.
The unconventional method of custom injection molding, known as overmolding, produces a part or product that is flawlessly integrated with several different materials.
It typically consists of a rigid, plastic-base component that is covered with a thin, pliable, thermoplastic elastomer (TPE) exterior layer or other materials using either a two-shot or multiple-shot molding technique. In some cases, it may also include additional components.
After considering the numerous benefits offered by the overmolding technique, you may find that it is an excellent choice for the next project you undertake.
● Achieving a stylish appearance that attracts consumers
● Reducing shock and vibration
● Dampening the sound
● Offer electrical insulation to products
● Improvement in the chemical and UV resistance
● Lengthen the life of products
● Give products a softer touch exterior
● Enhance visual grip of the physical outlook of the product
Overmolding not only enhances product viability but also increases overall customer satisfaction, which leads to a reduction in manufacturing costs. So it's not difficult to understand why plastic overmolding is a big deal for manufacturers.
When overmolding a hard plastic substrate with soft TPE, the surface of the hard component becomes soft and molecular diffusion in the outer layer occurs. The prerequisite is that the two materials, the TPE compound and the engineering plastic, must be compatible with each other, which means they can’t repel each other's molecules. As the molecular mobility increases, the molecules of the two materials spread out, which creates what's called melt adhesion. The molecules of the two materials form a network in the surface layer, and the network forms cohesive bonds between the materials.
1) Material chemical bonding
The compatibility of the materials is analogous to that of a mechanical adhesive. When these two materials come into touch with one another, it forms a bonding layer on the contact surface between the hard plastic substrate and the soft elastomer, it makes the rubber adhesion between the TPE soft rubber and the hard plastic significantly improved. The material's solubility parameter (SP) is the primary determinant of whether or not two substances are compatible. The solubility parameter should be as near together as possible to provide maximum compatibility between the two materials in overmolding.
2) Mechanical interlock structure
Product design, mold design, surface finish, and mechanical interlock mechanism (undercut, hole, rib, etc. ) make it possible to link the soft and hard plastic together.
The method of overmolding creates a plastic part or component by fusing two or more plastic materials into a single mass, which is the end product of the process. The same materials may be utilized, but it's also possible that other materials may be used. The potential permutations of the materials are practically limitless.
For us to have a more transparent comprehension of how the process functions, it is necessary for us to have an understanding of its two components. Every overmolding job may be broken down into two distinct phases. The substrate is the initial step in the process, and then the overmold is the next step.
The substrate is the substance that serves as your foundation. It might be constructed out of virtually any plastic material out there. The secondary material is the over mold from another mold. It refers to the substance you wish to "mold over" the substrate into the desired shape.
Depending on the circumstances, there may be two or more overmolds performed during the operation. The amount of overmolds required depends entirely on the intended final result and the producer's level of inventiveness. We often refer to more one time overmod as multi-shot molding.
The following is an overview of how the overmolding process works:
● Step 1: The first thing that is done is to mold a base component and then wait for it to cure. The substrates that are over-molded are frequently constructed of plastic. The substrate production is the same as conventional injection molding.
● Step 2: In the second step, a second layer is molded right on top of the first layer to produce a single piece that is solid throughout. Overmolding is a typical technique for producing plastic parts that include a screwdriver handle.
5. Substrate loading methods
● Manual loading substrates
In overmolding process, a traditional injection molding process is used to molding the substrate. The substrates are then put by hand into another mold for the next step, which is called "overmolding."
In the second layer of material cover, the substrate are put into the mold by an operator before the mold is filled. Manual loading substrate allows you to have detailed part inspections, assembly, packaging, or kitting done at little or no extra cost since there is a full-time operator. Maximize the saving on the cost. Most low- to medium-volume overmolding is done by hand, which is the most common method. But for more high-volume significant projects, it may be too expensive or inefficient to load inserts by hand.
● Automation robot loading substrates
Using servo automation tools during the robot loading substrate, we can ensure the consistency of parts quality. Moreover, robotic systems can feed substrates into the mold more quickly than a human operator can, which means more parts can be made in an hour at a cheaper cost per unit. Cost effectiveness, quality assurance and production continuity are the fundamental reasons why most manufacturers choose automatic loading inserts when forming large volume overmolding plastic parts.
1) Automotive
The overmolding process occupies a very important position in the manufacture of auto parts. The interior parts we often see, including handles, car seat and headrest parts, car under-hood accessories, etc. are produced by overmolding.
When overmolding technology was immature, these components alone were often fabricated from metal for durability. With overmolding in recent years, these components have been replaced by the overmolding process, which cannot achieve the lightweight and durability of automobiles. It is an ideal molding process for many automotive plastic parts.
2) Electronic & electrical
Many plastic parts in the electronics industry are overmolded to Encapsulate sensitive electronic components and cable connections.
The most widely used overmolding in the electronics industry is the packaging of PCB, thermostat products. In this type of overmolding, electronic components are first placed in a mold. Once they are positioned, they are coated with molten plastic, which is solid to form a protective plastic layer. This process was chosen to reduce the risk of damage by sealing the connection point between the wire and the connector. The production of almost every electronic product you can see involves some level of overmolding. USB chargers or HDMI cables in our lives are typical applications of overmolding.
3) Hardware Industry
An excellent illustration of overmolding may be seen on various instruments used in the hardware industry. Tools like screwdrivers, pliers, wrenches, hammers, tape measuring devices, pocket knives, blades, and other similar implements are examples of this category.
It can be challenging to use standard tools like these if the handles do not have an overmolding, whether one is replacing vehicle components or working on a home improvement job in general.
4) Power tools Industry
The fundamental reason why cladding is widely used in the power tool industry is that it can provide anti-seismic, grip effects and reduce the damage caused by motor vibration. Most power tools can be used in harsh environments or at high altitudes, but flexible handles formed from elastomer materials provide strong support. We commonly have an electric drill, saw, electric pick and so on are the most typical application of overmolding.
5) Medical devices
Many medical devices are required to have a rigid substrate with a soft overmold. product's safety that should be considered in the medical business. More than that, these tools must be sterile and in a condition where they may be quickly cleansed to forestall all forms of infection and medical concerns. Defibrillators, medical cables and wires are often packaged in plastic, with overmolding that both protects fragile internal components and makes the finished device easier to clean and use.
6) Consumer Goods
As was previously noted, overmolding may enhance the grip, use, and cleanliness of various items. Overmolding can also use materials to increase a product's resistance to chemicals, vibration dampening, sound insulation, and many other features.
Overmolding is used to create a wide variety of commonplace objects, including but not limited to toothbrushes, cooking utensils, portable electric fans, disposable razor handle multi-port chargers, shampoo bottles, reusable food containers, and the like. Even if it's just by making them simpler to clean, use, decreasing wear and tear, and extending the shelf life, overmolded items are made to enhance the user's experience and quality of life.
7. Two-Color Mold Injection - The Best Overmolding Solution
This technique, also known as double-material injection molding, typically involves two molds, one of which is mounted on a stationary plate of the machine and the other on a rotating plate. While each mold produces identical males, the female versions are distinct. Below is a short overview of how this process unfolds:
Once male and female molds are opened during the injection, molding of the first color of plastic. After the male mold and product have been spun clockwise 180 degrees once, the injection molding for the second color can be carried out, and the two-toned product extracted. Each molding cycle will produce both semi-finished and final goods.
● Once male and female molds are opened during the injection, molding of the first color of plastic.
● After the male mold and product have been spun clockwise 180 degrees once, the injection molding for the second color can be carried out, and the two-toned product extracted.
● Each molding cycle will produce both semi-finished and final goods.
The advantages of two-color injection molding:
1. The two actions are completed on one machine, without stripping action, and the substrate has no warping, which minimizes the possibility of occurring flash during the second overmold.
2. When the substrate finish molding, still is hot, with no secondary heating and can be overmolded directly, increasing the adhesion of the two materials, increasing product quality.
3. One action can complete two injection moldings, directly complete the final product, saving labor costs.
4. Two time molding is completed by one injection molding machine to ensure the stability of quality and continuity of production.
8. Advantages and Disadvantages of Overmolding
1) Advantages
Overmolding incurs high additional mold (usual two molds) and production (molding two times) expenses. However, the overmolding method provides the following benefits:
● Vibration damping and a nice touch
The handles of power tools provide high friction and seismic resistance, This is not provided by other processes. The soft elastomer can protect components (such as electronics) from vibration, which can prevent products from physical impact and prolong service life. it can be formed in any shape, making it great for ergonomics and giving you good touch. It raises the quality and performance of the product.
● Strong Grip
In general, the tool’s handles usually require something to help the operator maintain grip. Most importantly, overmolded grips are safer for the operator by providing greater grip, especially in wet conditions and working at high altitudes.
● Product Quality and Performance Improvements
Over-molding guarantees that matching pieces are appropriately aligned and rigidly assembled. Overmolding is combined with a variety of materials at high temperatures. Compared with the assembled products, its firmness and performance are incomparable. The process ensures the performance and life of the products and improves customer satisfaction.
● Removes fasteners and adhesives
Overmolding eliminates the need for additional fasteners or glue. A toothbrush rubber grip, for example, is two-shot molded with a plastic handle. As a result, overmolding removes the need for glue.
● Enhance the product's ergonomics and user experience
Soft similar rubber grips aid in the improvement of product ergonomics. it can be added to tools, toothbrushes, and other portable goods by overmolding. Two-shot molding and co-injection molding have applications in the production of multi-colored products. The use of many colors improves the overall appearance of the product.
● Parts are less expensive
Plastic overmolding removes the need for secondary procedures, lowering labor costs, time, and fastener needs.
● Increased Design Flexibility
Overmolding allows for complex assembly design and the production of multi-material components. Multi-shot molding is used to make automotive headlights.
2) Disadvantages:
Despite the numerous advantages of overmolding, a few drawbacks must be addressed before selecting to employ this procedure. These disadvantages include:
● High cost problem
Overmolding plastic parts are manufactured in a two-step process. This lengthens the part cycle time and costs more than molding a single component with no overmolding. This also needs two molds or a complicated two-shot mold with higher initial costs. Overmolding becomes a value-added option the alternative is to use vertical rotary injection molding, it needs two” B” molds and then joins them after the fact. It increases efficiency and saves cycle time.
● Debonding occurs
This is common when the injection temperatures are not in the appropriate range or no compatibility, or adhesion for the particular material combination. Mechanical interlocks may be necessary for specific circumstances when materials can’t be adequately bound together using intermolecular forces.
9. Overmolding Product Design Considerations
The various part design factors to consider during overmolding process include:
1) Uniform Wall Thickness
Wall thickness is a crucial aspect of the manufacturing process because it determines how effectively the overmolding material will flow around or through the substrate. Injection molding requires a steady temperature and pressure within the mold, but overmolding material will flow over a cold substrate, this can lead to warping, flashing, and short shots (incomplete fill of overmold).
The most straightforward technique to prevent difficulties with a hot material flowing over a cold material is to ensure that the wall thickness of the substrate and overmold is uniform. thin-to-thick transitions hinder the flow and lead to faulty components. During this process, it's essential to know that if the substrate's wall thickness is too thin, this hot molten material may melt it and cause it to fail if it flows over it.
2) Surface Finish
Another crucial aspect to consider during this phase is the surface finishing of the part. Depending on the product type and manufacturing requirements, the overmolding process offers a polished or textured surface finishing in the mold making stage. Especially for some anti-slip and shockproof overmolding products, the design stage of the relevant surface should be treated.
3) Structure
Before the overmolding process, it is vital to know the product's design well. Then, this design is analyzed according to the molded product usage, industry demands, and application. As per these aspects, you can easily create the design for product manufacturing.
4) Material Selection
When selecting the material for production, as per the design and usage demands, it's essential to choose from the materials that fulfill most production demands; it includes meeting the product/usage and overmolding compatibility, adhesion, flow performance, hardness, and friction. Furthermore, it is easier to avail of impactful manufacturing outcomes and final product if you focus on each aspect following the overmolding process.
5) Bonding
When it comes to using the overmolding process for part designing, bonding is another crucial factor you must not overlook. Bonding emphasizes the chemical and mechanical interlocking of the overmolding process and the products/material you choose to proceed with within the manufacturing process. For effective manufacturing of the product, it's crucial to ensure that the chemical and mechanical bonding of the product and process get along instead of being reactive. Certainly, mechanical interlocking(holes, grooves, ribs, etc structure) helps strengthen bonding.
10. Overmolding Mold Design and Making Considerations
Mold design is particularly important in the whole overmolding process. Many key factors play a decisive role in the success or failure of the project. We summarize our experience as follows:
1) Support
The plastic substrate needs to be adequately supported in overmolding applications. The TPE injection pressure can deform the plastic substrate if it isn't supported. When pressure is applied, the TPE will melt and invade through the plastic insert, or the insert will break. Furthermore, displacement of the insert within the mold cavity can also cause flashing in specific locations of the tool. Because the mold's "B-half automatically supports the first shot," this is rarely an issue with two-shot molding.
2) Shut-offs
A crucial thing to consider during the overmolding process is shut-offs. Shut-offs in the overmolding mold design are crucial for stopping TPE flow at the exact geometric position and preventing unwanted random edge flashes.
Here are some suggestions for overmolding shut-offs:
● The overmold must properly seal the substrate surface to obtain a clean edge between the substrate and the upper mold. Offer interference fit of 0.020 to 0.05 mm can be designed in the overmold to compress and seal.
● Heat treatment shut off mold steel to a minimum of 50-55 HRC.
● Make the shut-offs employed as inserts if available, it helps mold maintenance.
● Pre-dry substrate and TPE material.
● Add a sharp transition area between molding the TPE edge and supporting substrate
3) Substrate Fixing
It is also vital to ensure that the substrate is firmly fixed during the overmolding process. This fixing guarantees that the product can withstand high-temperature pressure during the process without any errors or drawbacks.
4) Substrate Shrinkage and Warping
Most plastics exhibit moderate shrinkage, resulting in warping or shrinkage of the substrate. This situation is especially true for long, thin, no ribs plastic parts, where the substrate is thinner than the overmold, or parts made from a high shrinkage rate substrate material. In overmolding process, it may be causing the soft TPE to compress more than the substrate.
The following suggestions should be helpful:
● Use a substrate material with a low shrinkage rate.
● Stiffen the substrate section with stiffening ribs.
● Reduce the thickness of the overmolding material.
● Use a TPE with a reduced hardness.
● Reposition the gate or quantity to reduce the flow.
5) Venting System
The overmolding venting system is also a crucial part involved in this process. With the presence of this venting system at the time of injecting the plastic material into the mold, air from the mold cavity and the feed system is vented outside the mold. Usually, placing the venting directly at shut-off edges.
Here are some suggestions about overmolding mold venting system design:
● This is usually achieved via the addition of vents at the ends of molten plastic flow.
● Venting dimension suggestion:
Land Length: Minimum 0.040" or 1 mm (where vent depth is cut)
Depth of Land (vent run out): >0.060" (>1.5 mm)
Vent Depth: 0.0005"– 0.001" (0.013mm – 0.025mm) deep — 0.00075" (0.019mm) optimum
6) Gate
One mistake that is easy to make when designing an overmold is to ignore to account for gate type, placement and quantity. Below are some common types of gate and their placement criterion that you should consider during the mold designing process.
● Tip gate
The conventional placement of a mold's gate is at the geometric center of the core side. But if overmold that extends over the part's edge or the mold's parting line will require an alternative gating solution. It is an innovative way of creating holes at the back of the substrate, as its the injection gate.
● Edge gate
Edge gates are named by their location on a mold along the mold's edges/sides. They are a versatile form of gate that can be used for many applications. Furthermore, they typically have a big rectangular cross-sectional area and are more easily adjusted than most valves.
● Submarine or tunnel gate
Below the mold separation line is a tunnel gate. This enables automatic trimming of the component during ejection. However, this type of gate is often tiny, resulting in a high-shear gate that allows only a limited amount of molten plastic to pass into the mold cavity. As a result, tunnel gates are only effective when used to mold small pieces. Using them for more significant components would result in unnecessarily long cycle times and unsatisfactory finishes owing to shear heating.
● Cashew gate
Because a cashew gate is installed below the part line, it is excellent for automatic trimming. In addition, it has a one-of-a-kind design that arcs around the component. As a result, this feature virtually eliminates any touch with the item, making this a perfect gate choice for a smooth finish.
● Fan gate
Fan gates are on the sides of a mold and are usually more expansive than the runner that leads up to them. So, they make it possible for more molten plastic to flow into the mold. Because of this, they can be used to manufacture significant parts.
Apart from these crucial ones, some other types of gates that should be considered when you are working on the mold design phase include pinpoint gates, diaphragm gates, hot runner valve gates, and hot runner thermal gates.
11. Overmolding Production Considerations
1) Machine Selection
During the process of overmolding, it's essential to consider the following points while selecting the ideal machine:
● For overmolding or multi-shot molding, use a rotary or shuttle machine whenever possible. It is beneficial to improve production efficiency.
● The shot size should be between 25% and 75% of the barrel's capacity.
● At processing temperature when operating, the molten material maximum time should stay in the barrel place should be 8 to 10 minutes. If the time is too long, the raw material is easy to degrade. When beginning production, or if the molding press has been idle for more than 10 minutes, it must be purged before production can resume.
2) Drying
The manufacturer must think about dryers when they need to dry the raw material. To be sure you're on the right track, follow the product technical data sheet for each type of plastic material. It will tell you what to do to ensure your project goes well.
3) Coloring
The color masterbatch carrier must be compatible before overmolding. Now the presence of wax in color concentrate may hinder adhesion. It is mainly because PE carrier inhibits adhesion. To avoid this, utilize the color carrier guidelines from the Technical Data Sheets. In addition, the color concentration must be considerably less dense for easy dispersion than the primary elastomer chemical.
4) Regrind
Regarding elastomer regrinding, For SBS formulations, regrind content should not exceed 25%. Black materials can better handle high degrees of regrind. Natural, light-colored, or transparent compositions will readily reveal contamination or discoloration. Organic pigments that generate yellow, red, blue, and green hues are more susceptible to color alteration with increased residence time or regrind levels.
5) Injection Pressure and Speed
Generally, the needed or attained injection pressures range between 30 and 100 bar. The benefits of shear thinning can be acquired if the injection speed is regulated to fill the mold in one to three seconds.
6) Melt Temperature or Barrel Temperature
In overmolding, the melt temperatures need to be higher than usual to get the best bond strength. In some critical situations, this temperature can be close to the highest temperature at which the TPE can be processed. Most melting points are between 200 and 220°C.
Reduce the temperatures in the back of the injection unit as much as possible and only keep the last zone and nozzle at the high processing temperature. As a result, this will reduce the time the material stays at high temperatures.
7) Substrate Temperature
The higher temperature of the substrate, the better bonding can be achieved. The bond strength can be improved by preheating substrates. preheating also can reduce the surface moisture of the substrate and improves adherence.
8) To get the most satisfactory bonding in two-shot molding, keep the delay between shots short
The shorter the interval time of two time molding, the less the deformation of the substrate, and the less the chance of the substrate being contaminated, this not only can improve the efficiency but also ensure the consistency of product quality.
12. Differences Between Overmolding vs. Insert Molding
Insert Molding and overmolding appear to be quite similar. However, there are minor distinctions between them. These differences include:
● In contrast, to insert molding, overmolding is a two-step technique in which a plastic component is molded over a previously molded component to create a single component.
● In contrast, Insert molding accomplishes the same goal in a single process. The distinction lies in the manufacturing process. The insert is positioned within the mold to create the final result.
● Another essential distinction is that insert molding is not limited to plastic and may incorporate metals with various items. the insert main is a metal or hard part which can withstand high temperature pressure at injection molding. Such as brass, aluminum, stainless, magnets, etc.
● Overmolding is typically used to create items with appealing textures, forms, and hues, primarily for shelf appeal. Insert molding is used to make items with greater rigidity or some functional object.
13. Factors Affecting Adhesion For Overmolding
While different manufacturing approaches, processes, and measuring properties are considered during the overmolding process, both the product, machine, and procedures are involved in this manufacturing process. Among all, certain processing conditions may have a more substantial influence on adhesion, shaping the end result of the product as well as the properties/quality of the product. These conditions include:
1) Injection temperature of the elastomer
Sufficient heat must be transferred from the melted TPE to the matrix to facilitate diffusion and entanglement of the polymer chains. Therefore, the best adhesion is obtained when the substrate is softened or melted. This is why preheating the substrate for over molding is recommended. In general, Higher temperatures result in greater bond strength.
2) Injection molding hold time
The ideal pressure hold time is the time required for the gate to freeze. So, a "gate freezing analysis" can be used to determine the best hold time to achieve optimal bonding
3) Hardness of the material
The lower the hardness, the better the adhesive. When the soft TPE material is fused with the hard substrate, the TPE softer, the more obvious the molecular force of the two materials is, and the bonding is stronger.
4) Texture
A textured surface increases the area over which adhesion can take place. In general, The rougher the surface, the better adhesion.
5) Additives, fillers also can affect two material adhesion
6) Material itself chemical compatibility
When the molecules of two materials repel each other, it means that there is no possibility of compatibility between the two materials. In this case, the compatibility can be increased by adding additives, fillers or changing other materials
7) Mechanical Interlock
Mechanical interlocking can improve bonding between the substrate and overmolded plastics
8) The thickness of the TPE layer also affects the bonding strength
Thin TPE layers tend to rapidly release heat in the cold chamber, and a drop in temperature tends to reduce the bonding strength. The challenge for designers was to strike a balance between the hardness and thickness of the TPE to achieve the desired level of buffering.
9) Mold design and part design
The physical blend between TPE and substrate depends heavily on the chemical compatibility of the material, including miscibility and interfacial tension. TPE needs to be chemically modified to adhere to specific substrate materials in order to match its polarity and solubility parameters. Anything that interferes with the "mixing", such as moisture or release agents, will adversely affect the chemical interactions at the interface.
14. Common Overmolding Problems and Solutions
● Edge of Substrate Flash:
This problem may be caused by incorrect analysis, substrate shrinkage, substrate warpage, mold shutoffs, etc. For mold issues, fix mold or wire cut edm etc way. For injection molding pressure too large or temperature too high also lead to this issue, decrease molding pressure and temperature should aid in resolving these issues.
● Bonding Issue:
The primary cause of this issue during overmolding is insufficient adhesion or the absence of a mechanical interlock. The solution to this issue is maintaining the hardness range between 30 Shore A and 70 Shore A. Higher injection temperature, texture, etc. add mechanical interlock increase adhesion. You can see above about more factors affecting adhesion and solutions.
● The Edge of the Substrate Collapsed:
If the substrate is porous and very thin, the edge may collapse during overmolding. Therefore, it is essential to prevent the edges of the substrate material from being exposed. A raised edge of substrate material can prevent peeling at the edges of the over-molded elastomer.
● Cross-Color Issue:
It occurs when the molding temperatures of two materials are incredibly close, resulting in a distinct melting point temperature difference. You can resolve such an issue by controlling the rear zone temperature, screw RPM, and back pressure. Such as PP and TPE material overmolding very easily to occur this issue.
● Crushed Part's Surface:
This problem may be caused by the substrate warpage. Maintaining uniform and consistent wall thickness for both the substrate and the overmold material is a potential solution to this problem.
More issue, the below table should be can help you:
15. Rotary or Shuttle Table Vertical injection Molding
Insert molding and overmolding benefit from vertical injection machines. Vertical molding involves opening and closing molds on the y-axis, enabling gravity to perform the work of holding substrate or inserts in the mold and removing the requirement for a custom-made mold. In addition, vertical injection molding machines take up very little space on the floor because of their setup.
Furthermore, vertical injection molding machines are built with open clamps and rotary tables. This enables work with two or more "B-half" molds and simultaneous operations, enhancing efficiency, productivity, and cost savings. Now when it comes to performing vertical injection molding using a rotary or shuttle table, the following process is followed:
● A horizontal injection unit or a robot is used to place a substrate in the B cavity in the first position.
● Then, the table revolves or shuttles to the next station, where the second layer of plastic (usually TPE) is injected with the help of another horizontal or vertical injection device.
● Afterward, a third table revolution sends it to a "off-load" station, where the completed plastic component is expelled.
1) Advantages:
● Vertical injection molding machine mold is opened in Y axis, gravity fixed the substrate, won’t be in the process of closing the mold due to dislocation or damage the mold.
● With the vertical molding machine injection overmolding, substrates can be easily and quickly put into the mold. Increasing production efficiency and product quality.
● Due to the action of gravity in the process, the required pressure and clamping force are lower than those of the horizontal molding machine
● For the vertical rotary table design of the injection molding machine, the substrate are fed into and molding completed at the same time(because with two “B-half” mold), more safe and efficient production, so as to reduce production costs.
● Vertical injection molding machine occupies half or even less space than traditional horizontal molding machine
2) Disdvantages:
● Vertical injection molding machine than the traditional horizontal injection molding machine clamping force is small, so, vertical injection machine is not the best choice for manufacturing large surface areas overmolding plastic products
● For a vertical injection molding machine to be fully automated, it needs to use a robot to pick up parts. Due to this reason, the machine slows down and makes its usage less efficient.
● The vertical injection mold is flat, once the mold is opened, the parts will not fall out. Must be removed by hand or robot.
● Manual parts removal steps may lead to inconsistent cycle time, which will have some impact on product quality consistency.
16. When is Overmolding Used
Overmolding is a popular approach to fulfilling production and manufacturing needs. Manufacturers employ this procedure to generate/manufacture products for various sectors, including the medical, cosmetic, automotive, and electrical industries.
While overmolding is a highly versatile manufacturing method, there are situations where it may make sense to use a different process. Overmolding is best for quickly producing large quantities of the same parts. Especially for need high requirements and nice ergonomics and a good touch with the plastic product. For those interested in making a small number of niche products, the upfront cost of overmolding may not be worth it in the long run. Molds can be more expensive than standard injection molding. This cost comes from the additional materials needed to manufacture the substrate and die tooling, as well as the precision needed to align the parts during the dying process.
17. The Most Suitable for Overmodling Material –TPE
TPE is being used extensively in the overmolding process. Because TPE material has strong slip resistance and elastic touch, it may increase the product's touch feeling and grip. TPE may also be changed to the suitable hardness (Shore 25-90A hardness range) and physical properties (such as abrasion resistance, scratch resistance, adhesion index, melt index, and so on) according to the physical qualities of the goods. For various items, a wide range of material uses is available.
Handles, grips, electronic materials, and other applications where the physical qualities of the material may add considerable value to the product are frequent uses for TPE overmolding. Because TPE is a green and ecologically valuable raw material.
18. Conclusion
Overmolding is an excellent procedure for connecting two different pieces to minimize assembly, give color contrasts, provide an ergonomic grasp, seal a region, or conceal known flaws in the substrate. Overmolding requires careful consideration at every stage of the design and manufacturing phase because of its potential impact on the final product. Moreover, while the initial investment in overmolding during product development may be higher, the long-term savings in production costs and increased product value may be worth it.
For professional consultation and services on the overmolding design and manufacturing processes, our team of experts is accessible around the clock.
