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Learn More About Sink Marks In Injection Molding And Choose The Best Company For You.

Sink Marks in Injection Molding: Causes, Prevention, and Solutions

Injection molding is a popular industrial procedure for making huge quantities of plastic parts. However, sink marks on molded components are a typical problem that can occur throughout this procedure. Sink marks are depressions or dents on the surface of plastic objects that can have an impact on their look and structural integrity. In this blog article, we’ll look at the reasons of sink marks in injection molding, as well as efficient preventative methods and professional solutions from EX MOULD Co., Ltd, a recognized firm with 9 years of expertise in sophisticated mold creation.

What Causes Sink Marks in Injection Molding?

Sink marks are caused by uneven cooling and solidification of the plastic inside the mold. Sink marks are caused by a variety of reasons, including:

Thick and Thin Wall Sections: Differential cooling rates are caused by variations in wall thickness, resulting in sink marks in thicker parts.

High Melt Temperature: Excessive melt temperature might cause delayed cooling and sink marks after solidification.

High Packing Pressure: Overpacking the mold might result in sink marks when the material cools and compresses.

Inadequate Venting: Inadequate mold venting retains air, resulting in uneven pressure and sink marks.

Material Selection: Because of their cooling properties and shrinkage rates, certain materials are more prone to sink marks.

Prevention Techniques

Sink marks may be avoided with careful design, accurate molding settings, and material selection. Here are some effective preventative measures:

Uniform Wall Thickness: To promote equal cooling and to reduce sink marks, pieces should have uniform wall thickness.

Optimized Molding Parameters: To achieve optimal mold filling and solidification, adjust injection speed, packing pressure, and cooling time.

Proper Venting: Include enough venting ports in the mold to let trapped air to escape and avoid pressure differentials.

Material Selection: To limit the risk of sink markings, use materials with low shrinkage rates and acceptable flow qualities.

Expert Solutions from EX MOULD Co., Ltd

EX MOULD Co., Ltd stands itself as a reliable solution supplier for treating sink marks in injection molding. The firm has 12 years of expertise in precision plastic mold design, manufacture, and injection molding. Their areas of competence include:

Cold Runner Mold: Molds that are efficient and developed for a variety of applications, guaranteeing balanced filling and less sink marks.

Hot Runner Mold: Precision molds with continuous material flow that reduces the danger of sink marks.

Insert Mold: Molds that have been expertly created for inserting metal or other components, providing even cooling and eliminating sink marks.

Epoxy Mold: High-quality epoxy molds with excellent surface polish and minimal sink marks.

Frequently Asked Questions

Can sink marks be completely eliminated in injection molding?

While total eradication is difficult, careful design, material selection, and molding procedures can limit the occurrence of sink marks dramatically.

How does mold temperature affect sink marks?

The cooling rate of the plastic substance is affected by the temperature of the mold. By achieving homogeneous solidification, proper mold temperature management can help reduce sink marks.

Why choose EX MOULD Co., Ltd for sink marks injection molding solutions?

With 9 years of experience in complicated mold building, EX MOULD Co., Ltd provides tailored solutions, innovative technology, and unrivaled skills to successfully address sink marks.


Learning what produces sink marks in injection molding is essential for making high-quality plastic components. Manufacturers may reduce sink marks and improve overall product quality by following appropriate design principles, optimizing molding settings, and using the suitable materials. When it comes to skilled solutions, EX MOULD Co., Ltd is a dependable partner, offering top-notch mold designs and injection molding services geared to successfully solve sink marks. For outstanding outcomes in your injection molding projects, rely on their 9 years of experience and concentrate on difficult mold construction.