What Is Gas Assisted Molding?

 Gas Assisted Molding (GAM) is an advanced injection molding technique used to manufacture plastic parts with complex shapes and hollow sections. This process involves injecting a pressurized gas, usually nitrogen, into the molten plastic inside the mold. Here’s a detailed explanation of how gas assisted molding works, its advantages, applications, and key considerations:

 

How Gas Assisted Molding Works

 

1. Injection Phase:

   - The molding process begins by injecting molten plastic into the mold cavity, similar to traditional injection molding.

   - The plastic partially fills the cavity, leaving some areas unfilled to be expanded by the gas.

 

2. Gas Injection Phase:

   - Once the plastic is partially injected, pressurized gas (typically nitrogen) is introduced into the mold.

   - The gas pushes the molten plastic towards the mold walls, creating a hollow section inside the part.

 

3. Packing and Holding Phase:

   - The gas continues to exert pressure, ensuring the plastic fully conforms to the mold’s surface and compensating for material shrinkage.

   - This phase helps achieve a consistent wall thickness and reduces the risk of sink marks and warping.

 

4. Cooling and Ejection Phase:

   - After the part has sufficiently cooled and solidified, the gas pressure is released.

   - The mold opens, and the finished part is ejected.

 

Advantages of Gas Assisted Injection Molding

 

1. Material and Cost Savings:

   - Reduces the amount of plastic required by creating hollow sections, leading to significant material savings.

   - Lower material usage translates to cost savings and lighter parts.

 

2. Improved Quality:

   - Reduces internal stresses and warping by evenly distributing the plastic within the mold.

   - Minimizes surface defects like sink marks and enhances the aesthetic quality of the parts.

 

3. Enhanced Design Flexibility:

   - Allows for the creation of complex geometries and intricate designs that are difficult or impossible with traditional injection molding.

   - Facilitates the production of parts with varying wall thicknesses.

 

4. Cycle Time Reduction:

   - Faster cooling times due to the reduced volume of plastic.

   - Increased production efficiency and reduced cycle times.

 

5. Structural Benefits:

   - Produces parts with higher stiffness-to-weight ratios.

   - Hollow sections can enhance the structural integrity of parts without adding extra weight.

 

Applications of Gas Assisted Molding

 

Gas assisted molding is widely used across various industries due to its versatility and the quality of parts it produces. Some common applications include:

 

1. Automotive Industry:

   - Production of lightweight components like handles, trim parts, and structural elements.

   - Enhances fuel efficiency by reducing the weight of automotive parts.

 

2. Consumer Goods:

   - Manufacturing of durable and aesthetically pleasing items such as furniture, appliance housings, and electronic enclosures.

   - Ideal for producing ergonomic and visually appealing products.

 

3. Industrial Components:

   - Creation of robust and lightweight industrial parts like tool handles, machine covers, and equipment casings.

   - Suitable for parts that require complex shapes and consistent quality.

 

4. Medical Devices:

   - Used to produce medical equipment and components that require precise and complex designs.

   - Ensures high quality and reliability for medical applications.

 

Key Considerations

 

1. Material Selection:

   - Not all plastics are suitable for gas assisted molding. Materials should have good melt flow properties and the ability to form a solid skin quickly.

   - Commonly used materials include polypropylene (PP), acrylonitrile butadiene styrene (ABS), and polycarbonate (PC).

 

2. Mold Design:

   - Mold design is critical to ensure proper gas flow and effective plastic distribution.

   - Considerations include gas injection points, venting, and the ability to withstand high gas pressures.

 

3. Process Control:

   - Precise control over gas pressure, injection timing, and plastic flow is essential to achieve consistent quality.

   - Advanced monitoring and control systems are often employed to manage these parameters.

 

4. Cost Implications:

   - Initial setup costs for gas assisted molding can be higher due to specialized equipment and mold modifications.

   - However, the long-term benefits of material savings and improved part quality often outweigh these initial expenses.

 

Conclusion

 

Gas Assisted Molding is a sophisticated injection molding technique that offers numerous benefits, including material savings, improved part quality, and enhanced design flexibility. Its ability to produce complex, lightweight, and high-quality parts makes it a valuable process in various industries. Understanding the principles, advantages, and considerations of gas assisted molding can help manufacturers leverage this technology to optimize their production processes and achieve superior results.

The Ultimate Guide to Gas Assist Injection Molding

 

 

What is Gas Assist Injection Molding?

Gas assist injection molding (GAIM) is an enhanced injection molding process often applied for complex parts, large parts and parts requiring an attractive, cosmetic finish.

The types of parts benefiting most from this process include:

• large panels
• enclosures
• handles
• doors and bezels
• tube or rod-shaped parts

How Does Gas Assist Work?

The gas assist process is introduced at the finish of the mold filling stage while the resin is still liquid.  Pressurized gas (usually nitrogen) is used in place of pack pressure from the molding machine.  The pressure from the gas completes the filling of the mold cavity, forcing an even distribution of molten resin against the mold. The gas is held inside during the entire cooling phase and then is vented, leaving a hollow void.  For internal gas-assist molding, the void is inside the plastic.  For external gas assist molding, the void is on the outside surface, typically the backside of a part.

Benefits with Gas Assist

The gas-assist process gets results when part design elements make the part difficult to manufacture using straight injection molding.  GAIM allows for more design flexibility while still being able to provide these benefits:

• Thin-walled parts with greater strength and rigidity
• Creation of hollowed out areas, reducing part weight
• Reduction of molded-in stress for improved dimensional stability
• Better surface finish with no sink marks
• Less part shrinkage and reduced warpage

Design Advantages with Gas Assist

1. Complex Designs

For the design engineer, using GAIM expands design options and helps to minimize design changes to make the part manufacturable using injection molding. One of the greatest benefits is the ability to produce complex parts.  Oftentimes with straight injection molding, parts having different wall thicknesses are molded separately and assembled later.

GAIM allows multiple parts to be combined into one, reducing the need for secondary assembly processes – even if the parts have different wall thicknesses.  This is because gas-assist allows heavy wall sections to intersect thinner ones. Support ribs and bosses can achieve tighter tolerances and be designed larger without fear of sink marks. Gas channels are directed toward these areas and the consistent pressure during the cooling phase eliminates sink marks, associated with these support features, on the front side of the part.

2. Metal Replacement

Gas-assist allows the production of thin-walled components that have solid but hollow areas.  The resulting strength and lightweight part can often replace metal fabricated or die cast parts, and reduce product cost.

3. Large parts

The introduction of gas pressure aids in mold filling, providing uniform pressure throughout the part that lasts through the cooling stage. The result is a part with less shrinkage and reduced warpage. Part weight can also be reduced by creating hollowed out areas.

4. Cosmetic finishes

Where an attractive finished surface is required, gas-assist prevents sink areas that eliminate or at least minimize secondary operations to improve part appearance including sanding and priming.

5. Hollow parts

The gas can create hollowed out areas within parts like handles, which decreases part weight and still provides strength.

 

 

Cost Benefits with Gas Assist

1. Extended Tool Life

With gas-assist, lower clamping force is required because lower pressures are used.  This results in less mold wear extending the life of the tool.

2. Less Energy Cost

With lower clamping force required, larger molds can be used in smaller presses.  Smaller presses consume less power and help to decrease the cost of manufacturing the part.

3. Less Machine Time

A more rapid cooling period helps to reduce cycle time which in turn lowers manufacturing expense per part.

4. Lower Material Cost

Less material is used to produce the part because hollow areas inside of the part are created with the gas and with less resin used, the part cost is lowered.

5. Quality Results

With gas-assist injection molding, the process is typically easier to control than conventional injection molding. A dependable, repeatable process provides consistent production results and less waste.

Common pitfalls

There are many common pitfalls when it comes to Gas Assisted Injection Moulding. Firstly, it is more complex and more expensive to set up than ordinary injection molding. if the tooling price of injection mold shocks you, gas-assisted injection molds will blow you away. Also, by introducing gas into the molding mix, this variable must be precisely tracked, managed and controlled. Without experienced machine operators and technicians, the molding process could go disastrously wrong. The control of the gas also contributes to variable wall thicknesses, especially in tight corners and this is something you generally want to avoid.

Gas Assist Tool Design

If you want to achieve high-quality results, make sure you get the tool design right.

Regardless of what injection molding process will be used, it is important to engage your molder during the early stages of part design in the design for manufacturing (DFM) phase. Tooling cost, timeline, and resulting part quality will be directly impacted by the quality and efficacy of the tool.  When determining the optimal way to mold apart, engineers will consider all product requirements including application, resin selection, and cost considerations. Mold flow analysis is used to find design constraints so that adjustments can be made. When the tooling engineer determines gas-assist is the best solution, the tool will be designed with gas channels built into the mold that will allow the addition of nitrogen gas during the molding process. Determining your molding method early will conserve tooling costs and help to maintain project timelines.  Getting your molder involved early will be critical to a cost-effective, high-quality product.

 

To learn more about this process or to receive assistance with your project, contact WIT MOLD.

Advantages And Differences Of Two Shot Injection Molding

There are a variety of manufacturing methods used to manufacture products that use plastic polymers, including two-shot injection molding, compression thermoset molding, and extrusion. Although all of these are viable manufacturing processes, this process has several advantages that make it the first choice of many plastic manufacturers. The process is relatively simple; inject one material into the mold to make the initial part of the product, and then inject a second material that is compatible with the raw material. Many manufacturers use this method to make plastics or polymers for three good reasons.

 

Two-shot injection molding is cost-effective

The two-step process only requires one machine cycle, the way the initial mold is rotated and the product placed around the second mold, so that a second, compatible thermoplastic can be inserted into the second mold. Because this technology uses only one cycle, rather than a separate machine cycle, any production operation cost is lower, and fewer employees are required to manufacture the finished product while delivering more projects per run. It also ensures a firm bond between the materials without the need for further assembly down the line.

Two-shot injection molding

 

Strengthen product quality

Two-shot injection molding improves the quality of most thermoplastics in the following aspects:
Improved aesthetics. When products are made of different colored plastics or polymers, they look better and are more attractive to consumers. If more than one color or texture is used, the product will look more expensive.
Improve ergonomics. Because this process allows the use of a soft-touch surface, as a result, items can have ergonomically designed handles or other parts. This is especially important for tools, medical equipment, and other hand-held items.
When silicone plastic and other rubber materials are used for gaskets and other parts that require a strong seal, it provides a better seal.
It allows you to combine the outstanding comfort and practicality of hard and soft polymers with even the smallest products.
Compared with overmolding or a more traditional insertion process, it can greatly reduce the number of dislocations.
It enables manufacturers to create more complex mold designs using multiple materials that cannot be effectively bonded by other processes.
The bond created is very strong, creating products that are more durable, more reliable, and have a longer lifespan.

 

Versatility

Product manufacturers favor two-shot injection molding, with a wide range of applications, including automotive interior parts, medical equipment, tools, and toys. It allows manufacturers to combine various materials and colors to create final products that are both strong and attractive. 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 dilemma. An experienced plastic manufacturer can guide you through the process from concept to finished product and ensure a cost-effective solution.
We are Two-shot injection molding suppliers. Please feel free to contact us if you need or want to know about our products.

Pros And Cons Of Thermoset Injection Molding

Weighing the pros and cons of the molding process for your composites can help you determine whether it is the right choice for your project needs. Manufacturing plastic or composite parts requires heating and pouring the raw materials into a mold that has been specially made for the part. The four most common molding processes are:

ㆍCompression

ㆍInjection

ㆍTransfer

ㆍExtrusion

Different molding processes are used to create different works. In this article, we will weigh the pros and cons of the injection molding process for thermoset composites.

Advantages of thermoset injection molding

Injection-molded parts may be the most suitable one for several reasons:

ㆍMany different types of materials can be used for injection molding, including thermoplastics and thermosetting resins, polymers, and elastomers. This provides engineers with a lot of control over which hybrid material will produce the best results, especially when it is necessary to meet specific performance requirements.

ㆍVery suitable for high-volume operation.

ㆍPrecision and low waste. Due to the specific mold and material combination, compared with other processes, there is less waste of injection molded parts.

ㆍShort cooling time-the injection molded parts cool quickly, reducing the time required for the injection molded parts to be released from the mold.

 

Thermoset Injection Molding

Disadvantages of thermoset injection molding

For the above reasons, injection molding is an excellent process, but it also has certain limitations and defects. These disadvantages include:

ㆍMold costs – these costs can be very important because precision-made molds are required.

ㆍFlash – Flash is inevitable when injection molding thermoset plastics. Once the part is created and ejected from the mold, the next step is to automatically or manually remove the flash (excess material). Due to the high viscosity of liquid plastics, a flash of thermoplastics is not a problem.

ㆍPart size – The size of the part being created is very important in the molding process. Typically, smaller part sizes (0.1 lb to 6 lb) are injection molded, while larger parts are transfer or compression molded. The number of orders will also determine which molding process is best for the project. Compression molding may be used for smaller parts with a low (or high) volume, while transfer molding may be used for medium to high volume projects. Injection molding will be ideal for large-volume running smaller pieces.

Finally, when choosing a molding process for your part, it is always recommended to talk to a thermoset composite or thermoplastic engineer. After assessing your needs, they will be the most capable and able to make suggestions for your work and provide the highest quality products at the most reasonable cost.

We are a thermoset injection molding supplier. Please feel free to contact us if you are interested in our thermoset injection molding or other products.

Just How Tolerances Influence Injection Molded Plastics?

 

What Is Tolerance?

The tolerance stated in the plastic injection mold is an engineering requirement. In basic terms, they are allowable variants to the initial dimensions of the parts or the base dimension. As it is impossible to generate a product that purely abides by the base measurements, some leeway obtains factored into the design of items.

This margin ensures that all measurements for molded products fit the setting up demands. For example, you may wish to produce products with a size of 2.8 mm. Nevertheless, attempting to produce them might end up with some of them gauging 2.6 mm.

What tolerances do is to establish minimum as well as optimum values for the production process in a way that ensures the product fits. In this case, the reduced limit can be evaluated 0mm while the ceiling is readied to 0.3 mm. By doing this, you are assured products whose diameters range between 2.8 mm and also 3.1 mm.

The important of tolerances

Generating plastic parts for your products calls for that their measurements fit perfectly. It’s very easy to offer dimensions for the type of components you want; obtaining them to have similar measurements to your requirements is a virtually impossible venture to achieve.

The type of making procedure you go for also has a terrific bearing on the high quality of completion product. Injection molding is among the most effective processes you can experience with standards like hubbub 16901 to name a few, but it’s still unable to produce parts with the right fit.

The only escape of such a scenario where it’s impossible to get an exact suit is to leave area for some distinctions in dimension. They don’t need to be major; they simply require not interfere with the item style. This is where tolerances are available in.

What Influences Tolerance?

The kind of polymer utilized throughout the creation of your items substantially identifies whether the tolerances are within acceptable limitations. As distinct polymers obtain injected into the plastic mold, they cool as well as shrink at different prices.

Despite the fact that these shrinkage rates can be quickly represented, completion product will certainly have different tolerance ranges and also discrepancies from the acceptable varieties. The array is a dimension of the difference between the biggest as well as tiniest measurements of measurements in the created batch.

Various other aspects that figure out tolerance consist of the style of the product, the intricacy of the style along with the atmosphere the injection molded parts will certainly be running in.

Minimum/Good Tolerances for Plastic molds

The great, or rather, minimal tolerances are established by the plastic polymer you choose to use for your products. These tolerances also can be found in various forms. For one, there are dimensional, straightness/flatness, and also hole diameter tolerances. They are also divided right into business tolerances and precision tolerances, which are greater in price.

Considered that an injection-molded physical tightening is a result of the cooling, the facet of temperature level decrease is influenced by various other aspects as well. They include the thaw thermal reading, the cooling price, the thickness of the part, the dimensions of eviction, as well as much more.

Furthermore, a section of the molded product that is thicker than an additional will certainly experience even more shrinking. All these variables are since even though it is possible to forecast the behavior of the plastic polymer you wish to be molded; the material will never ever act as anticipated 100% of the time.

The polymer concerned might likewise experience warpage. This is particularly real with parts that are non-uniform as they shrink at various rates in comparison to components that have uniform wall surface thickness. These non-uniform components can happen whenever the part’s design has a concern.

The final words

WIT MOLD has become one of the best molds in the industry because we combine the essence of the latest technology with proven traditional methods.

With an expert team composed of experienced and knowledgeable experts, we are able to complete custom orders for Custom Plastic Molds and parts that may exceed the capabilities of our competitors. We are also unremittingly committed to improving customer satisfaction, which includes providing comprehensive end-to-end quality assurance for every product we produce.

Three Questions You Need to Consider before Choosing Precision Molding

If you need a plastic part molded with extreme precision—for example, to ensure there’s no air leak between two molded sections or to be certain there’s no visible seal gap line—you likely require precision molding. The difference between a typical injection molded part and a precision molded part is the tolerance, or acceptable range of variation in dimension: While the majority of injection molded parts have a tolerance of +/- .005″, precision molding holds tolerances between +/- .002″ and +/- .001″ (or less, in some cases).

Let’s say, for example, you’re planning to manufacture a military projectile. In order for the projectile to fit properly in the firearm, handle the acceleration when it’s launched, and explode on impact, it requires very high precision.

If your application requires precision molding, you can’t leave anything to chance—so you’ll want to ask yourself the following three questions before you begin the process:

 

1. Have you selected a plastic material with low shrinkage?

The plastic material you select for your part makes a big difference in whether you’ll be able to do precision molding. For example, polypropylene has a shrinkage range of +/- .014″ to +/- .022″, with an average of +/- .018″. This is a wide range for shrinkage, which makes hitting a specific tolerance extremely difficult. If you’re molding a toothbrush (which commonly uses polypropylene), dealing with shrinkage isn’t a big concern, as the toothbrush will function appropriately regardless of whether it’s slightly bigger or smaller than its counterparts. Acrylonitrile butadiene styrene (ABS)—another common thermoplastic polymer—has a much narrower shrinkage average of +/- .006″. That gives you a much better chance of hitting a tighter tolerance, but it still won’t reach the +/- .001″ or +/- .002″ tolerance needed for a precision part.

One way to hit high tolerances with your plastic material is to add glass or another filler resin (like carbon fiber or mica) into the material. This can minimize shrinkage and warp by providing more structure in the material. For example, if you include long glass fibers in a polymer material, the part will shrink more perpendicular to those fibers.

2. Have you determined which areas of the mold require precision?

Because precision molding is more expensive than typical injection molding, be certain which aspects of your part require tight tolerances—and whether those tolerances can be achieved through injection molding—before moving forward. For example, a surgical handle may only require precision for the piece that will connect with a pin, not the entire handle. Identifying your precision requirements from the get-go ensures you’ll get what you need without wasting money. In the case of the surgical handle, your injection molding partner may advise you to add the tolerances you need through tooling after the injection molding process is complete.

3. Can the mold manufacturer you’ve selected tool with high precision?

The process of creating plastic parts with tight tolerances begins with a high-precision mold. If each plastic part you create is not identical, you won’t have a precise product—and a precise mold ensures there’s no variation for each part. Because of this, it’s extremely important to select a mold manufacturer who understands the slow, steady process of building a high-precision tool. Keep in mind that selecting a mold manufacturer that specializes in rapid tooling is likely not your best option, as the goal of rapid tooling is to finish the mold quickly—but not necessarily precisely.

Let’s get your precision molding project started

We have years of experience in precision molding, and would love to answer any and all of your questions. You can either contact us with those questions, or, if you’re ready to get your project started now, simply contact us and request a free quote.