Maintaining optimal wall thickness is crucial in custom injection molding. Thick walls waste material and can lead to defects like sink marks, while thin walls risk warping, cracking, and reduced durability.

Striking the right balance ensures strong, high-quality, and cost-effective parts. This blog is all about deciding the minimum wall section thickness for the injection molding parts.

What is Wall Thickness in Injection Molding?

Wall thickness is the space between an exterior surface and an interior surface of a part that has been molded. This is crucial for the strength, sound structural disposition, and responsiveness of a component. It is advisable to consider a wall thickness of not less than 1.5 mm to 4.5 mm at most.

The thickness is conditioned by the type of application and material. Minimum wall thickness ensures strength and the absence of problems that can occur at the stage of manufacturing.

Importance of Minimum Wall Thickness for Injection Molding Parts

The importance of minimum wall thickness for injection molding parts is as follows: 

1. Dimensional Stability

Too thin walls can deform or even fail under stress. They are likely to compromise the structural integrity of the part. On the other hand, if the walls are made too thick, it will increase the weight. This will result in the wastage of material. 

2. Efficient Manufacturing

Thin walls cool faster than thick walls. This reduces the cycle times in injection molding. Too thin walls may create filling problems or defects like sink marks or voids. 

3. Properties of Material

The distinction in the properties of materials makes their wall thickness different. For example, a high melt flow index can be used for thin walls while a low melt flow index for thick walls.

How to Determine Minimum Wall Thickness?

For determining the minimum wall thickness for injection molding parts, one should consider the following:

1. Selection of Materials

The plastic material is a principal factor that affects minimum wall thickness. Each material has its mechanical properties and flow characteristics. It controls how thin a wall can be without adversely affecting its performance.

When selecting a material for injection molding parts, it's crucial to choose one that meets both functional requirements and ideal wall thickness. Different materials have varying properties that affect their suitability for thinner or thicker walls. Refer to the table below for recommended wall thickness ranges for common injection molding materials to help guide your decision.

Recommended Wall Thickness for Common Injection Molding Materials

This table shows recommended wall thicknesses for some common injection molding materials.

2. Part Design and Geometry

It should be noted that the thickness of the wall depends on the design of the part that is installed. Structures that require more strength or structural support, may require thicker walls and the opposite for others. For example, each wall should have a uniform thickness to prevent difficulties concerning cooling and shrinking. 

3. Flow Length and Filling 

The flow length is the distance which is covered by the plastic in a molten condition within the mold. Thinner walls increase flow restrictions. The thickness of the walls must be increased to enable proper flow of material into the regions with complex shapes or long fluid paths. 

4. Cooling Rate and Shrinkage

Thicker walls take longer to cool than smaller ones, resulting in warping or internal stress. The designer should consider the different materials' shrinkage rates while designing wall thicknesses. 

5. Designing Ribs for High-Strength, Thin-Wall Injection Molded Parts

To maintain thin walls while ensuring strength, ribs are a great alternative to increasing wall thickness. However, their effectiveness depends on proper design:

• Optimal Thickness: Ribs should be 50-60% of the wall thickness to prevent sink marks.
• Ideal Height: Keep rib height ≤3× the wall thickness to ensure proper mold filling.
• Spacing Matters: Maintain a gap of at least 2× the wall thickness between ribs.
• Draft Angle: A minimum 1° draft helps with easy mold release.
• Strong Intersections: Use radii of 0.5-1× the wall thickness at junctions for added durability.

6. Consider Adjacent Walls in Your Design

Wall thickness is not an isolated factor—adjacent and nearby walls play a crucial role in determining the minimum requirement. To ensure proper flow and avoid issues during the final fill, no wall should be thinner than 40-60% of its neighboring walls. If the thickness falls below this range, the flow may stall, leading to incomplete fills and potential defects in the final part.

Conclusion

Determining the minimum wall thickness for injection molding parts is a process with multiple stages. It requires an analysis of material properties, part design, flow dynamics, and cooling rates. Following standard guidelines and improved simulation techniques helps the designers optimize their products. The maximum strength-to-thin wall ratio leads to successful injection-molded products. 

Mech Power is your trusted partner for high-quality plastic injection molding. We work closely with you to optimize your part designs, ensuring strength, precision, and consistency in every product. From selecting the right plastic material to refining complex features like ribs and reinforcements, we help you achieve the best results.

With our expertise, we ensure efficient and reliable production, delivering high-quality injection molded parts tailored to your needs. Try Mech Power’s injection molding services for your enclosures and experience quality you can count on. Call us today to learn how we can help with your special needs! Connect with us at [email protected], or you can call us at (+91) 9898412126. Submit your inquiries regarding our injection molding services here.