10 Plastic Injection Molding Defects and Their Prevention

Nov 24, 2020

Common Plastic Injection Molding and Their Preventions 

In this article, we will be discussing 10 plastic injection molding deformities to keep an eye out for and how you can dodge them.

Some defects might be troublesome or expensive to address. Others can be forestalled by making small changes. There's a great deal of space for costly mistakes with regard to plastic injection molding.

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They can be brought about by issues identified with the embellishment cycle, material use, tooling plan, or a mix of each of the three. Now, we shall take a look at the most widely recognized mistakes identified and what you can do to prevent them.

Plastic Injection Molding

Stream Lines or Flow Marks in Plastic Injection Molding

What do we mean by streamlines?

Streamlines are waves, streaks, or lines that are stained when contrasted with their surroundings. These are generally seen near the 'entryway', where the liquid plastic enters it through injections. They don't influence the usefulness of the item, however, make the item lose its aesthetic.

How to prevent it?

  • The easiest response to this issue is to fasten the injection molding process
  • The weight and temperature of the material infused into the form can be changed so the plastic can totally fill the shape prior to setting.
  • Another procedure is changing the area of the shape entryways of the injection units where the liquid plastic starts to stream in during the assembling cycle.
  • Applying an oil to the surface will help the progression of the liquid thermoplastic material.


Burn Marks

What are burn marks?

Burn marks are dim shaded blemishes on the edges of the item. However, they don’t have any bad effects.

How to prevent it?

  • Burn imprints can be maintained by a strategic method of lessening the injection speed and holding the weight of the embellishment device. This will forestall air bubbles getting caught inside
  • Gas vents can be augmented to encourage a simple getaway of caught air.
  • Decreasing the temperature of the form and water-driven chambers can also help forestall burn marks


What does warping mean?

Warping happens when various pieces of an item cool and sets unevenly. The resultant item is distorted with twists in it.

How to prevent it:

  • Make the cooling cycle slow so that there is no weight on the liquid plastic material as it cools.
  • Change the temperature during large scale manufacturing.
  • Use materials that don't recoil unnecessarily during cooling.

Vacuum Voids/Air Pockets

What do we mean by air pockets?

These are caught air bubbles in the finished item. Despite the fact that this isn't viewed as a significant imperfection, it could make it a bit weak.

How to solve it effectively?

  • The blow plastic injection compel should be expanded to remove the caught air that rises out of the shape.
  • Select a material with low consistency so that air bubbles are not shaped in it without any problem.
  • Guarantee that there are entryways close to the thickest pieces of the shape so the plastic doesn't cool too early.

 Plastic Injection Molding Sink Marks

What are sink marks?

These are little miseries shaped in the plastic item. This typically happens when the internal portion of the segment cements quickly.

How to prevent this?

  • A basic method to amend this issue is increment the weight so that there is more opportunity for the material to cool

Weld Lines

What are the weld lines?

These are lines that show up on the outside of the plastic item. It happens when liquid plastic emerges from various channels at one point in the form and bonds feebly to one another. This outcome is debilitating to the plastic part at the weld line.

How to fix it?

  • The material temperature should be expanded so that there is uniformly cementing of the material
  • The infusion speed and weight can be expanded to guarantee that there is no untimely cooling inside the shape.
  • A material with lower thickness can be picked as the crude material so it streams effectively and doesn't cool rashly.


What does the term ‘Jetting’ mean?

Jetting is brought about by an unexpected wave of liquid material, which then begins to cool before the remainder of the hole is filled, prompting unusual changes on the outside of the item.

How to prevent it?

  • One approach for streaming in plastic segments is to decrease the infusion pressure. This will forestall the squiring of the liquid material into the form.
  • The temperature of the form and material can be expanded so that the wave stream doesn't cement quicker than the remainder of the material.
  • Ideal planning of the shape and responding screw so that streaming doesn't happen is another solution.

Plastic Injection Molding

Plastic Injection Molding Discoloration

What is discoloration?

Discoloration is the point at which the completed plastic item is of unexpected color in comparison to what it should be. Discoloration doesn't influence the quality or working of the completed item.

How to get rid of discoloration?

  • Ensure that all pieces of the plastic injection molding machine like the container, spout, form, and so on are altogether cleaned before you run a new group.
  • Cleanse the machine routinely to eliminate any remaining material.
  • Ensure that your provider provides shading specialists with adequate warm solidness and that your crude material is properly blended

Surface Delamination

What does surface delamination mean?

Delamination is when thin layers from the completed item begin to strip away from its surface. This is a major issue, as chipping of the surface material would, in the long run, cause the item to debilitate and lose its usefulness.

How to prevent it?

  • Ensure that the material has been dried appropriately prior to stacking it into the container of the machine.
  • Be cautious of the capacity and treatment of the crude material to avoid pollution.
  • Overhauling of the spout would be beneficial in ensuring that toxins don't enter the shape

You May Also Read: Plastic Molding Company: Introduction to Molding Process

Short Shot

What does the term ‘Short Shot’ mean?

During the process of plastic injection molding, if the liquid plastic material doesn't fill in the form entirely, the end result will have defects and be left unfinished after it cools down.

Effective way to solve this problem:

  • One way is to update the shape with bigger doors so the resin can move without any problem.
  • The plastic injection speed and weight should be controlled to improve the stream.
  • The shape temperature can be expanded to forestall untimely cooling of the material.

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