What are ten injection moulding defects their causes and remedies?

1. Flash

Flash is a thin layer that extends beyond mold cavities’ edges. Flash is usually caused by an excess of material injected into a mold cavity or a gap between two mold halves.

Flash can be corrected by manufacturers who adjust injection pressure and speed or alter the design of the injector to close the gap between mold halves.

2. Warpage

Warpage refers to a distortion of the molded parts. This is usually caused by poor injection mould design or uneven cooling.

Manufacturers can alter the cooling time, mold temperature or design of molds to correct warpage. This will improve material flow.

3. Sink marks

Sink marks are indentation on the surface of an injection-molded part. These marks are usually caused by an insufficient or incorrect flow of molten plastic material within a mold cavity. Manufacturers can adjust the injection pressure and speed to correct sink marks.

4. Blisters

Blisters are raised, small areas on the injection-molded part. Blisters are usually caused by trapped air or gas in the material or improper venting.

Manufacturers can decrease the injection pressure, speed or alter the mold design to remedy blisters.

5. Weld lines

Weld lines are visible flow lines or seams on the surface of the molded component, where two streams of material meet and fuse. 

They are typically caused by improper flow of the material within the mold cavity, or by a lack of fusion between the two streams of material. 

To remedy weld lines, manufacturers can adjust the injection pressure or speed, or modify the design of the mold to improve the flow of the material.

6. Short shots

Short shots refer to incompletely filled mold cavities. This can result in a shorter injection molded part than was intended.

These problems are usually caused by insufficient or incorrect flow of material within the mold cavity. Manufacturers can adjust the speed or pressure of plastic injection to correct short shots.

7. Voids

Voids are hollow spaces or empty spaces in the injection-molded part. Voids are usually caused by air or gas in the material or improper venting. Manufacturers can adjust the speed or injection pressure to correct voids.

8. Burn marks

Burn marks are areas that appear darkened or discolored on the surface of an injection molded part. These marks are usually caused by excessive heat or poor mold design.

Manufacturers can modify the design of the injection mold or reduce the temperature of injection to correct burn marks.

9. Bubbles

Bubbles are hollow areas or voids within the molded part, caused by gas being trapped within the material flow during the injection molding process. 

They can be caused by a variety of factors, including air entrapment, improper venting, or contamination of the material. 

To remedy bubbles, manufacturers may need to improve the venting of the injection mold, remove any sources of contamination, or use a material with a lower gas content.

10. Ejector pin marks

Ejector pin marks are small circular marks made on the surface of a molded part by the ejectors that were used to remove it from the mold.

These are usually caused by incorrect mold design or placement, or improper ejection from the injection mould. Manufacturers can alter the design or location of the ejector Pin to correct ejector mark.