Best Practices for Wall Thickness in Injection Molding


Wall thickness significantly influences the demands that the injection molding process places on the material, equipment and tooling. Inadequate wall thickness can lead to higher defects, such as sink marks due to insufficient melt pressure.

On the other hand, too thick walls may result in lower productivity due to increased cycle times and material usage. Thus, it is vital to maintain an optimum wall thickness to balance these competing demands.

Some of the best practices for thick wall molding include:

a) Optimizing the wall thickness about the dimensions of the part

This practice helps to ensure that the wall thickness is balanced across the whole part. It also helps to avoid areas of the part that are too thin or too thick. When the wall thickness is optimized, it helps to reduce the overall cycle time and material usage.

b) Keeping the wall thickness as uniform as possible

This practice helps to minimize the risk of defects, such as sink marks. It also helps to improve the overall aesthetics of the part.

c) Avoiding sharp corners and transitions

Sharp corners and transitions can result in thin spots in the wall thickness, which may be more prone to defects. It is essential to avoid sharp corners and transitions and instead opt for gently rounded corners or gradual transitions between different areas of the part to minimize these risks.

d) Using thick-walled inserts where appropriate

Thick-walled inserts can be used in areas of the part that require extra strength or rigidity. It helps avoid the need for excessively thick walls in the rest of the part, leading to increased cycle times and material usage.

e) Selecting the suitable material

The material selection is another critical consideration for wall thickness. Some materials are more prone to sink marks than others. It is best to avoid materials with high melt flow rates and instead opt for materials with lower melt flow rates.

When it comes to wall thickness in injection molding, a few best practices should be followed to ensure the highest quality parts. By following these practices, it is possible to balance the competing demands of productivity and quality, resulting in parts that meet the application’s needs.

These are some of the benefits of using these practices:

Reduced cycle time

The cycle time can be reduced when the wall thickness is balanced and uniform across the whole part. There are fewer areas that require extra time to cool or fill.

Reduced material usage

Keeping the wall thickness as uniform as possible makes it possible to reduce the overall material usage. It can help lower the cost of the parts and improve the sustainability of the manufacturing process.

Improved part quality

By avoiding sharp corners and transitions, it is possible to reduce the risk of defects such as sink marks. It can help to improve the overall quality of the parts.

Increased strength and rigidity

Thick-walled inserts can be used in areas that require extra strength or rigidity. It can help improve the parts’ performance and durability, making them suitable for a range of applications.

Greater design flexibility

Using these best practices can help open up a range of design possibilities, enabling manufacturers to create highly innovative and customized parts for their customers.

When determining the optimum wall thickness for a given application, some factors must be considered. These include:

The type of material being used

The materials used in injection molding have different flow characteristics, which affect the wall thickness requirements. For example, highly viscoelastic materials like PEEK may require significantly thinner walls than more dense materials like polypropylene.

The design of the part itself

Different component designs will place other demands on the material and equipment, requiring specific wall thicknesses to optimize productivity. For example, parts with thin ribs may require thinner walls overall than parts with thick bosses or tall walls.

The injection molding process and equipment being used

Different injection molding machines will place other demands on the material and tooling, which may require specific wall thicknesses to achieve optimum performance.

The desired level of quality and productivity

The wall thicknesses required to achieve the desired level of quality and productivity will vary depending on the application. However, it is crucial to maintain a balance between these two factors. It is essential to consider all of the above factors and tailor the wall thickness to the specific application to achieve optimum results. Doing so makes it possible to minimize defects, reduce cycle times, and improve both the quality and productivity of the injection molded parts.


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