KLARM MOULD Promote Quality Injection Molded Products by Eliminating Injection Molding Defects

Injection molding is an art, which involves science as well. Actually, injection molding requires great attention to detail as minor mistakes can cause a lot of financial loss to a company. In recent months, KLARM has made great efforts on eliminating injection molding defects to make high quality injection molded products for customers around the world.

Flow Lines

Flow lines may include lines, patterns, and streaks that appear on the prototype part because of the cooling profile or physical path of the molten plastic while it moves into the cavity.

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  • One way to fix the issue is to increase the pressure and injection speed, which will make sure that the mold will fill the cavities.
  • Another way is to round the locations and corners where the thickness of the wall changes.

Sink Marks

These are minor depressions or craters that form in the thicker areas when shrinkage happens in the internal areas of the end product.


  • Reduce the mold temperature, increase the holding pressure and time for better curing and cooling.
  • Reduce the thickness of the wall sections that are the thickest. This will allow faster cooling and prevent the sink marks.

Vacuum Voids

Vacuum voids refer to the air pockets inside or near the prototype surface. They occur because of the uneven solidification amidst the inner sections and the surface.


  • Find the gate at the mold’s thickest part
  • Opt for the plastic that is less viscous, which will reduce the amount of gas trapped.
  • Increase the holding time and pressure
  • Try to keep the mold parts aligned

Surface Delamination

Surface delamination happens when thin layers of the surface show up on the part because of a contaminant. Actually, these layers look like coats that can be peeled off.


  • Before molding, make sure you dry the plastic properly
  • Raise the degree of mold temperature
  • There should no sharp turns and corners in the mold design

Weld Lines

Weld lines show up on an area where the liquid plastics mixes while they flow from different mold parts.


  • Increase the temperature of molten plastic or mold
  • Raise the injection speed
  • Make adjustments to the design to ensure that the flow pattern is only one source flow

Short Shot

A short shot refers to a situation that happens when a molding shot tends to fall short. In other words, the molten plastic won’t fill the cavity of the mold for some reason. As a result, it leaves a portion where you can see plastic.


  • Opt for a plastic that features higher flow and less viscosity
  • Raise the mold temperature for better flow
  • Get a machine that features more material feed

To cut a long story short, you may have to face a lot of defects during the process of injection molding. What you need to do is follow the tips given in this article to fix or eliminate these issues to make the process error-free.

About Us

Klarm Mould is a professional plastic Mold maker in China. The firm continuously tries to reach top excellence level in quality. They want to deliver customers with precision parts sold at competitive prices and delivered on time.

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