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.

An injection mold is a tool for producing plastic products and for giving them a complete structure and precise dimensions. Read on for more information about common problems and solutions for injection molds.

 

 

A mismatch between mold and injection molding machine

Causes:

1. Positioning ring position is not correct, size is too big or too small.

2. Wrong position and size of the ejector hole of the mold; wrong position and size of the forced pull reset hole.

3. Mold width size is too big; mold height size is too small.

Solution:

1. Adjust the ejector hole position and size; adjust the reset hole position and size.

2. Replace the positioning ring; adjust the position and size of the positioning ring.

3. Change the tonnage of a large injection molding machine; increase the thickness of the mold.

 

Bad quality of parts

Causes:

1. The fit-gap is too large.

2. Poor glue walking, trapped air.

3. Ejector pin is too small, uneven ejection.

4. Too small bevel, burr, hardness is not enough.

5. Uneven injection pressure, insufficient strength of product form.

6. Processing error.

7. Far from the gate, low mold temperature.

Solution:

1. Trim the gate, pressure uniformity, strengthen the product strength.

2. Reasonable adjustment of clearance and grinding work part of the parting surface.

3. Improve the gate, increase the mold temperature.

4. Add local glue, add exhaust.

5. Re-processing.

6. Increase the ejector pin, evenly distributed.

7. Repair burr, increase slope, nitriding.

 

 

The parts are difficult to fill and difficult to take

Causes:

1. The pouring system is blocked, the runner cross-section size is too small, the gate arrangement is unreasonable, and the gate size is small.

2. The limit stroke of the mold is not enough, the extraction stroke of the mold is not enough, the ejecting stroke of the mold is not enough.

Solution:

1. Check whether the limit, core extraction, and ejection strokes meet the design requirements and adjust the strokes that do not meet the requirements.

2. Check the runner and gate of each section of the pouring system, and fix the parts concerned.

 

Mold opening and closing ejecting reset action is not smooth

Causes:

1. Slanting ejector, ejector pin sliding is not smooth.

2. Mold frame guide column, guide sleeve sliding is not smooth, with too tight

3. Reset spring elasticity or pre-pressure is not enough.

Solution:

1. Increase or replace the spring.

2. Repair or replace the guide pillar, guide bush.

3. Check and repair the slanting top, ejector pin.

 

Mold water transportation is not working or water leakage

Causes:

1. Water sealing rubber ring and water pipe joint are not sealed enough.

2. The mold water channel is blocked and the inlet and outlet water pipe joints are connected in the wrong way.

Solution:

1. Check the cooling system inlet and outlet water pipe joints connection and each section of the waterway, repair the relevant parts.

2. Check the water sealing rubber ring and water pipe joints, repair or replace the parts.

 

WIT MOLD is a very professional mold design and mold manufacturer located in southern China and has passed the ISO2009:2015 international quality Our injection molding process can be customized according to your unique project. If you are interested, please feel free to contact us.

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.

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.

Two-Shot Molding vs. Overmolding

Injection molding is a popular manufacturing process, which can quickly produce complex-shaped precise parts without wasting a lot of materials.

Many different processes belong to the category of injection molding, including over-molding and two-shot molding. The two processes are similar, but there are some key differences-here are what engineers and designers need to know:

What is two-shot molding?

 

Two Shot Injection Molds, also known as dual-molds, double-shot molds, or multi-shot molds, are a subcategory of injection molding that allows engineers to create multi-material or multi-colored parts without adding additional assembly steps.

Through the different layers of materials or colors created by the injection molding machine, the two-shot injection molding process is best understood. The first material is injected into the mold to create the substrate, and other materials or materials will be molded around the substrate. After the substrate solidifies and cools, it is transferred by hand, robotic arm, or rotating plane to another cavity of the mold.

From there, the mold opens and rotates 180° with one side of the substrate to meet the other mold chamber and injection molding nozzle. Once the substrate is in place, the second material is injected and combined with the substrate to form a firm hold. Once the second layer has cooled, the last part will be sprayed out.

Engineers should know that Two Shot Mold can be accelerated or slowed down, depending on how the substrate is transferred to another cavity of the mold. Hand and robot arm transfer takes longer than the rotating plane, but the rotating platen molding is more expensive, usually, there are only high-efficiency options, mass production runs.

In addition, it is very important that the material of the mold is easy to bond, and the mold must be aligned to prevent deformation of the parts.

Advantages and disadvantages of two-shot molding

 

Two-shot injection molding is efficient and economical manufacturing technology. This process also produces highly durable terminal parts and assemblies.

From a design point of view, two-shot molding provides designers with a lot of flexibility, because this process can create complex geometric shapes and adapt to multiple colors to produce more beautiful parts.

In addition, because one machine manufactures the entire part, no post-processing is required, and engineers can greatly reduce manufacturing time, thereby reducing costs. However, it is worth noting that the initial two-shot injection molding machine may be costly, and the two-shot injection molding machine is more expensive than the standard injection molding machine. Fortunately, these costs are usually offset by labor savings and assembly costs for large-scale production runs.

What is over-molding?

 

Overmolding, like Two Shot Moulding, is a multi-shot injection molding process that produces a single final product from two or more different thermoplastics. This process is ideal for engineers who want to build components that are powerful, functional, beautiful, and that will not separate over time.

At the beginning of the over-molding process, engineers inject the substrate with a harder over-molding material. Then, the substrate is placed in an over-mold tool or an over-mold cavity within the same mold. The molten-over mold material is then sprayed into, onto, or around the substrate. After the molten material is cooled, the substrate and the over-mold are chemically or mechanically combined. The entire over-molding process only takes 30 seconds.

The product team must remember that all thermoplastics used in the over-molding process must be chemically or thermally compatible with each other. Compatibility with metal substrates is usually not a problem, because they can be used with any plastic over mold, but the product team may encounter compatibility issues when using plastic over molds. If the substrate and mold are not compatible, the final product may be deformed or poorly bound.

However, if two less compatible plastics must be used, the team can design mechanical bonding properties for the part after the fact, although this may result in higher costs.

Advantages and disadvantages of over-molding

 

Overmolding and two-shot injection molding have many of the same advantages. They are ideal for quickly creating durable, reliable, and vibration-resistant parts with complex geometries, but over-molding is best suited for low-volume production runs.

Compared with two-shot molding, over-mold design is also easier, because engineers can use any standard injection molding machine to carry out this process.

In terms of disadvantages, the tolerances of over-molded parts are often lower than those of two-shot injection molding. It is also important to remember that plastic compatibility requirements may constrain designers.