Common injection moulding process defects and solutions

Injection molding is a manufacturing process used to produce a wide range of plastic products and components.  It's a cost-effective and efficient way to create large quantities of identical parts.  However, like any manufacturing process, there are common defects that can occur during injection molding.  In this article, we'll explore some of the most common injection molding process defects and their solutions.

1.  Sink marks: Sink marks are depressions or indentations on the surface of a molded part.  They occur when the molten plastic cools and solidifies at different rates.  To prevent sink marks, designers can adjust the thickness of the part, use a rib design, or change the gating location.

2.  Warpage: Warpage is when a molded part doesn’t maintain its intended shape or dimensions.  This defect can be caused by uneven cooling or improper part design.  Choosing the right mold material, gate location, and cooling system, as well as designing the part with uniform thickness, can help prevent warpage.

3.  Flash: Flash is excess material that protrudes from the parting line or between two mold halves.  It's caused by a variety of factors, including too much injection pressure or inadequate clamp force.  Increasing clamp pressure, adjusting injection speed, or reducing material temperature can help prevent flash.

4.  Burn marks: Burn marks are black or brown discolorations on the surface of a molded part.  They are caused by excessive heat, and can be prevented by lowering the barrel temperature, adjusting the injection speed, or selecting a different material.

5. Short shots: Short shots occur when the mold doesn't completely fill with plastic, leaving voids or missing sections in the finished product.  This is often due to inadequate injection pressure, insufficient material in the barrel, or improper gate design.

Injection molding is a complex process with many variables that can impact the quality of the finished product.  By understanding the common defects that can occur, designers and manufacturers can take steps to prevent them.  By choosing the right materials, adjusting gate locations, and optimizing cooling and injection parameters, they can create high-quality products that meet their customers' needs.