What is Two-shot Molding

Two-shot injection molding is a multi-material injection molding process. The molded plastic part can be a combination of two different materials or a combination of different colors of the same material.

Two-shot molding can also be called 2k injection molding, double shot molding, multiple injection molding (sequential injection molding).

When two-shot molding be used?

ㆍProduct function requirements

For example, power switches, phone buttons, keyboard indicators, car switches, etc. Portion with an LED capable of transmitting light.

ㆍImprove the handle feeling

Some handheld products require the use of rubber in hand-held parts, which makes the hand feel more comfortable. For example, walkie-talkie housing, power tool handle, wrench, screwdriver handle, toothbrush handle, thermos, etc.

ㆍEnhance beauty

For example, some plastic parts have a logo. If you use two-shot injection molding, you don’t have to worry about it being erased.

ㆍA localized area of the product that needs to be plated

In the plastic range, only ABS and PSUsurfaces can be plated. If it is necessary to plate a part or a single side of the product, the plating area should be injected into the ABS. Areas that do not require plating are injected with other materials such as PC.

7 Suggestions for Product Design

 

Two-shot molding frees the designer’s creativity. However, the following factors should also be noted in the product design process.

No.1

Choose the right material. The figure below shows the compatibility of different plastics.

1 ) The core material can use low viscosity materials to reduce the injection pressure.

2) Consider from the perspective of environmental protection. The recycled material can be used as a core material.

3) Optimize the product according to the characteristics of different materials. For thick parts, the finished skin layer uses soft materials. The core material uses hard or foamed plastic to reduce weight.

No.2

If the material is not chemically compatible, the two materials can be integrated by mechanical interlocking.

No.3

Maintain proper draft angle, uniform wall thickness and smooth transition lines.

No.4

The surface of the part should be flush or slightly lower than any adjacent substrate surface.

No.5

The surface of the substrate is textured to improve the adhesion of the two materials.

No.6

The mass ratio of the two materials should not be too large. Factors such as material forming time and injection pressure should be considered.

No.7

By increasing the contact area of the two parts, the weld strength of the two materials can be enhanced.

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9 Suggestions for Two-shot Molding

 

No.1

The hard plastic is molded for the first time, and the soft plastic is molded for the second time. Transparent for the first time, non-transparent for the second time. The plastic with high molding temperature is molded for the first time, and the plastic with low molding temperature is used for the second molding.

No.2

Before the official production, test the mold to produce a complete product.

No.3

Identify all possible defects in the process and eliminate them before the mold is manufactured.

No.4

Consider the shrinkage of the two materials.In general, shrinkage is determined by the material that is first formed.

No.5

A second injection can only be made after the first injection has been completely completed.

No.6

Consider the molded position, to prevent damage in the process.

No.7

Allow the edge of the first injection molded part to be too large. This ensures a higher pressure during the second injection.

No.8

Ensure that the parameters of the injection unit provide the required pressure, flow rate and cooling capacity.

No.9

Ensure that the structural strength of the first molded part can withstand the injection pressure of the second molding.

6 Suggestions for Maintenance of Two-shot Mold

No.1

Check for loose or damaged fastening parts of the double shot mold. The solution is to find parts of the same specification for replacement.

No.2

After the mold has been used for a long time, the cutting edge must be cleaned and ground. After grinding, the surface of the cutting edge must be demagnetized, otherwise it will easily block the material.

No.3

Elastic parts such as springs of the two-shot mold are most susceptible to damage during use. Breakage and deformation usually occur.

No.4

The method adopted is to replace, and the specifications and model of the spring must be paid attention to during the replacement process.

No.5

Two-shotmold punch during use prone to breakage or bending. Damage to the punch and the sleeve is generally replaced with parts of the same specification. The parameters of the punch mainly include the working part size, the mounting part size, and the length size.

No.6

Check the pressure plate, top plate and other parts of the double shot mold. During maintenance, check the accessories of each part and whether there is any damage, and repair the damaged parts. Pneumatic ejector check for air leaks, and specific measures taken.

Conclusion

Two-shot molding increases the added value and productivity of the product. At the same time, plastics are becoming more and more colorful.

Correspondingly, the cost of two-shot molding is higher. Master the design points and avoid risks in advance. Avoid cost waste.

If you have any questions about two-shot injection molds, please contact us directly. Get a free quote.

There are a variety of manufacturing methods used to create products using plastic polymers, including two-shot injection molding, compression thermoset molding and extrusion. While all of these are viable manufacturing processes, there are several advantages to this process that make it the top choice for many plastics manufacturers. The process is relatively simple; one material is injected into a mold in order to make the initial section of the product, followed by a second injection of a secondary material that is compatible with the original material. There are three good reasons many manufacturers use this method of manufacturing plastics or polymers.

Advantages of two-shot injection molding

 

Two-shot injection molding is cost-effective

The two-step process needs only one machine cycle, rotating the initial mold out of the way and putting the secondary mold around the product so that the second, compatible thermoplastic can be inserted into the second mold. Because the technique uses only one cycle instead of separate machine cycles, it costs less for any production run and requires fewer employees to make the finished product while delivering more items per run. It also ensures a strong bond between the materials without the need for further assembly down the line.

Enhanced product quality

Two-shot injection molding enhances the quality of most thermoplastic items in several ways:

ㆍImproved esthetics: Items look better and are more appealing to the consumer when they are crafted of different colored plastics or polymers. The merchandise looks more expensive if it utilizes more than one color or texture
ㆍImproved ergonomics: Because the process allows for the use of soft-touch surfaces, the resulting items can have ergonomically designed handles or other parts. This is particularly important for tools, medical devices, and other hand-held items.
ㆍEnhanced sealing capabilities: It provides for a better seal when silicone plastics and other rubbery materials are used for gaskets and other parts that require a strong seal.
ㆍCombination of hard and soft polymers: It lets you combine both hard and soft polymers for outstanding comfort and utility for even the smallest of products.
ㆍReduced misalignments: It can greatly reduce the number of misalignments when compared to over-molding or more traditional insert processes.
ㆍComplex mold designs: It enables manufacturers to create more complex mold designs using multiple materials that can’t be effectively bonded using other processes.
ㆍExceptionally strong bond: The bond created is exceptionally strong, creating a product that is more durable, more reliable, and with longer life.

Versatility

Product manufacturers favor a wide range of applications for two-shot injection molding, including automotive interior parts, medical equipment, tools, and toys. It allows manufacturers to combine various materials and colors to create a strong and attractive final product. Some materials can be effectively combined with this process, including silicone and thermoplastics, nylon and thermoplastic elastomers, or hard nylon and soft-touch materials.

Two-shot injection molding can solve your company’s product production difficulties. An experienced plastic manufacturer can guide you from concept to finished product and ensure a cost-effective solution.

Producing an assembly with multiple components

Compared to other methods of plastic molding, two-shot is ultimately a more cost-efficient way of producing an assembly with multiple components. Here’s why:

Part Consolidation: Two-shot injection molding reduces the number of components in a finished assembly, eliminating an average of $40K in development, engineering, and validation costs associated with each additional part number.

Improved Efficiency: Two-shot molding allows multiple components to be molded with a single tool, reducing the amount of labor needed to run your parts and eliminating the need to weld or join components after the molding process.

Improved Quality: Two-shot is carried out within a single tool, allowing for lower tolerances than other molding processes, a high level of accuracy and repeat-ability, and reduced scrap rates.

Complex Moldings: Two-shot injection molding allows for the creation of complex mold designs that incorporate multiple materials for functionality that cannot be achieved through other molding processes.

Disadvantages of two-shot injection molding

1) High tooling costs and long setup lead times. Up-front costs are high due to the design, testing, and tooling required. There is the initial design and prototyping (probably via CNC or 3D printing), then the design of a prototype mold tool to produce replicas of the part in volume. Lastly, and only after extensive testing during both stages, you can finally inject mold a part.

2) Part design restrictions. Plastic parts must be designed with injection molding consideration and must follow the basic rules of injection molding, for example:

Avoid undercuts and sharp edges as much as possible

Use uniform wall thicknesses to prevent inconsistencies in the cooling process resulting in defects like sink marks.

Draft angles are encouraged for better de-molding.

Don’t forget, because tools are typically made from steel or aluminum, it can be difficult to make design changes. If you need to add plastic to the part, you can make the tool cavity larger by cutting away steel or aluminum. But in order to take away plastic, you need to decrease the size of the tool cavity by adding aluminum or metal to it. This is extremely difficult and in many cases might mean scrapping the tool (or part of it) and starting over.

Also, the weight and size of the part will determine the tool size and necessary press size. The larger the part, the more difficult and expensive it will be.

3) Small runs of parts can be costly. Due to the complexity of tooling, and the necessity to rid the machine of all previous material before the next product can be made, the setup time can be quite lengthy. Therefore small runs of parts have traditionally always been thought of as too expensive to injection mold.

 

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In plastic injection molding, the cooling rate is the last section of the molding cycle.

The cooling rate is a decreasing rate from the time the plastic resin enters the mold until the last cavity of the mold is filled.

When the cooling process is complete, it is safe to remove the part from the mold.

Factors that affect the cooling rate and the final molded part

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Mold Cavity Pressure

The cooling rate is monitored, measured, and displayed on a pressure curve. It is displayed this way because as the plastic resin cools, it shrinks, which reduces the mold cavity pressure.

Mold Temperature

In plastic injection molding, the temperature of the mold itself can be a factor in the cooling rate process. Aside from affecting mold cooling lines, mold temperature can affect part blemishes, like:

• Mold Warpage
• Sink Marks
• Jetting

Improper mold temperature can also impact properties, such as:

• Molded-in Stress
• Fatigue Resistance
• Wear Resistance
• Creep Resistance
• Molecular Weight
• Dimensional Stability

The cooling rate can also be affected by the use of metals that conduct heat away.

The cooling process is complete when the temperature is no longer reducing and any additional time spent to cool the part is useless.

When the cooling process is complete, it is safe to remove the part from the mold.

TIP: During the plastic mold design phase, you must consider the best possible cooling channels for the mold. Using a plastic molder with a deep knowledge of cooling rate process optimization will allow for better control over the mold temperature, and thus, the cooling rate. It will also provide the best cycle time and the best outcome for a good, stress-reduced molded part.

How to Calculate Cooling Time?

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Cooling time in injection molding is a critical part of the production process. It is the amount of time the molten plastic takes to solidify. An adequate cooling system is required to transfer heat away from the mold and maintain a stable cooling rate, ensuring the highest quality final products.

One of the quickest methods for estimating the cooling time is using a formula that accounts for the thickness of the part in an equation based on the effective thermal diffusivity. The thermal diffusivity estimates the transfer of heat in and out of material.

 

Since its establishment, WIT MOLD has successfully exported more than 2000 sets of molds with different types of structures and designs, which are applied to a variety of industries.

One of the most unique types of injection molds is unscrewing molds. Unscrewing molding is a unique injection molding process with mold technology that includes movement and rotation to produce threaded components. Some plastic parts such as caps and closures with detailed threads cannot be removed using standard knock-off methods. After they are molded, parts need to be carefully unscrewed from mold to avoid damaging the threads.

The unscrewing molds are part of everyday use, which may cause you to think that you won’t need to spend much time considering the required design. To demonstrate the wide use of this particular mold type, the following is a shortlist of the types of products that use unscrewing molds in the design:

 

• Bottle and milk caps

• Condition and shampoo lids

• Prescription medication bottles

• Medical supplies

• Sprinkler and showerheads

• Screws, nuts, and bolts

Here’s How It Works:

• First, the plastic is injected into the tool. After the plastic has cooled, the threaded core starts to unscrew. The unscrewing mechanism works off of a rack and pinion and is powered by a hydraulic cylinder.

• The rack turns three sets of gears which then retracts the threaded core into the ejector box.

• Once the threaded core is fully unscrewed, the mold opens and the ejector system pushes a stripper plate forward to eject the part.

• After the part is fully ejected, the hydraulic cylinder reverses, screwing the threaded core back into the molding position, and the process repeats.

 

What factors need to be considered?

When you need one of these types of plastic molds, there are several things you have to determine to make sure you get the right fit for your product and budget.

Volume

The volume of the product will probably determine many different aspects of the final product, including the thread count, the size of the part, and the type of material that will be used during production. While other factors are important, the design of the various unscrewing molds is more complex and costly than many of the other types of molds.

Ease of Removal

The ease by which an unscrewing mold should be removed from the final product is an important factor to consider in the design. Water bottles have only a few threads, sometimes only two or three because they need to be easy to remove. To ensure that the tops do not fall off easily, the threads are spaced out a bit more. An unscrewing mold on a medical device will likely need a lot of threads that are evenly spaced and very difficult to pull off of the device. The material required for these two vastly different uses is affected by how easily the part should be removed from the product.

The Threads

The number of threads is going to vary based on the final product. Water bottles do not require a high thread count because they are relatively light and should be easily removed. If the unscrewing mold is for a plastic part under the hood of a car, it needs to have a higher thread count to be more durable. The number of threads required plays a large role in the final cost of production, so it needs to be tested to ensure it meets the needs of the final product.

Applications and Maintenance

High volume, reliable unscrewing plastic injection molds are some of the more complex plastic injection molds that can be manufactured. Unscrewing plastic injection molds are typically utilized for high volume applications where threaded plastic parts are needed for items such as:

ㆍBottle caps

ㆍShampoo bottles

ㆍPharmaceutical Supplies

ㆍAutomotive parts

ㆍNuts and bolts

ㆍCosmetics packaging

ㆍMedical Supplies

ㆍConsumer goods

ㆍSprinkler heads, lawn & garden parts

ㆍContainer lids

 

Most threaded plastic parts on standard plastic injection molds are not easy to remove using standard knock-off techniques. Therefore more complex unscrewing plastic injection molds must be utilized to prevent the threads on threaded plastic parts from being damaged while the parts are coming off of the plastic injection mold.

Because these threaded plastic parts are typically needed in high volume applications for items such as bottle caps or cosmetics packaging, the unscrewing plastic injection mold most operate at a high speed to reduce cycle times thus reducing part costs. The unscrewing plastic injection molds must also be high quality and reliable to operate for a large number of cycles while only needing routine preventative maintenance.

 

WIT MOLD is a highly skilled mold design and manufacturing company in Southern China, certified ISO2009:2015 international quality standard. Contact us today for your threaded plastic parts!

 

Gas assisted injection molding is a process for producing big plastic to get rid of complicated designs as well as excellent ornamental surface area coatings. Continue reading to get more information about the advantages of gas assist molds.

Smooth surfaces

 

Gas assist injection molding likewise produces much smoother surface areas to attain the preferred style. After the plastic product has currently been expelled from the machine, it can already be fit for market distribution with really couple of alterations or secondary procedures needed.

With a smoother surface, producers do not need to make changes to the device– i.e. lowering stress, temperature level, and even the place of the gates. This is since gas assisting can already fix many of the problems that may result on the surface of the plastic. Smoother surface areas use a more aesthetically appealing as well as smooth design.

High functionality

 

In the regular injection molding process, there is no gas channel to transmit a low-pressure nitrogen liquid. This suggests that the process may take a lot longer time because there is no element that is quickening the flow of the material into the mold. As a result of the absence of this part, the material can be prone to bending as well as higher inner stress.

With gas-assist, nevertheless, internal stresses are substantially minimized in the resin, leading to a much faster and freer-flowing product. Integrated with properly maintained mold and mildew dental caries, any kind of product resulting from gas-assisted injection molding will conveniently be better compared to the alternative.

Fewer products needed

 

Depending upon the kind of material utilized, injection molding pellets can cost as much as $5 USD per kg. This, along with the expense of purchase and maintaining the elements of the injection molding device are currently costly alone.

Knowing this, makers take advantage of gas assist when they desire a reduced volume of material to be used. This produces cost-beneficial end results for both the maker as well as the end-user.

Using less product can help them save added resin pellets for future usage without giving up the top quality. When a consumer desires a model to be done, on the other hand, they could almost request the much more cost-friendly and also economical gas assist process.

Minimizes fabrication defects

 

There are lots of common sorts of injection molding flaws– from something as minor as circulation lines as well as staining to something as complex as distortion and warping.

To avoid these issues from occurring, injection molding tools operators need to embark on a series of modifications on the device. For instance, they might intend to create another mold and mildew layout, increase/reduce stress and also temperature level, and even utilize various resins entirely.

Gas assist offers a reliable as well as all-around service to these flaws. As claimed before, the low-pressure nitrogen gas is constantly and also uniformly sent to the molten material. It permits the product to be firmly pressed as well as portable itself onto the walls of the mold tooth cavity. The outcome– a high-quality product that’s devoid of stress and takes the intended design and shape of the producer.

 

 

Lighter

 

Plastic has actually been a preferred material for several sectors as a result of its lightweight residential or commercial properties. With the right tools and also maker handy, it’s feasible to come up with acrylic, HDPE, polyethylene, and even polytetrafluoroethylene injection-molded items that are less thick than the typical material yet can still be used in functional applications.

Like the materials over, materials that have undergone gas assist injection molding are far lighter in weight in contrast with the typical injection molding procedure. The main consideration for this is that the procedure uses up much less area and material, leading to a sturdier and also extra long-lasting product that is not also cumbersome.

Critical takeaway

 

Several benefits of gas assist injection molding consist of the following: much better dimensional quality, enhanced efficiency, much less product, lighter product weight, smooth surface areas, and much less warping.

For both manufacturers as well as end-users, the gas assist injection molding strategy uses a number of advantages. Before deciding on whether or not the gas assist procedure is the right one for you, establish your item needs as well as factors to consider such as production as well as procurement expense, parts needed, high quality of the material, and so forth.

Improved sizing quality

 

The procedure of setting up multiple or particular gas channels in a single plastic injection molding equipment is absolutely nothing brand-new. As a matter of fact, gas assist is widely made use of in producing specialty items– specifically those that have special dimension styles and patterns.

Ribbed plastic items, as they’re called, are the result of a finely-tuned gas assist injection molding strategy. This process is one of the most efficient selections for generating these stylized products as a result of the boosted dimensional precision as well as quality that it provides. You’ll frequently locate everyday materials like container caps, water drums, containers, as well as much more.

 

We are a gas assist mold supplier, please feel free to contact us if you need them.