What is mold void?

What is mold void?

Voids are a somewhat common defective occurrence in injection molding applications. They present as “air pockets” in transparent molding but can also be present in colored or opaque molding applications.

How do you fix voids in injection molding?

To solve voids or sinks, try slow fill rates, use of gas counterpressure, or increasing backpressure. Ensure the runner or gate is not freezing too early and that longer hold times will allow more packing during the second stage.

What are the defects in Moulding?

Technical Information｜Molding Defects and Countermeasures

• Insufficient resin amount.
• Insufficient injection pressure.
• Low filling speed.
• Low resin temperature.
• Insufficient release of air from the mold.
• Too small runner or gate diameter.
• Long runner.
• Thin wall thickness of the molded product.

What is sink mark and voids?

Sink marks appear as surface depressions (seen as dimples or grooves); voids are less obvious and may appear as bubbles in clear parts.

What is the main reason of voids?

Voids form when the outside layer of the part cools faster than the inner layer of the part. This causes the inner layer of the part to basically pull-apart causing the void to form. While good part design dictates having a uniform wall thickness, sometimes thicker walls cannot be avoided.

What causes vacuum voids in injection molding?

Causes: Vacuum voids are often caused by uneven solidification between the surface and the inner sections of the prototype. This can be aggravated when the holding pressure is insufficient to condense the molten plastic in the mold (and thereby force out air that would otherwise get trapped).

What causes flash in injection molding?

The causes of flash are numerous and include parting line mismatches, improper venting, low clamping pressure, low viscosity, and uneven flow. Some of these problems are related to tooling but others are a function of processing.

What causes voids in injection molding?

Voids form when the outside layer of the part cools faster than the inner layer of the part. This causes the inner layer of the part to basically pull-apart causing the void to form.

What are five moulding defects their causes and remedies?

Here are a few examples of defects that can occur in a molded part and ways to fix them:

• Flow Lines. Description: Flow lines are lines, streaks, or patterns that show up on the prototype, caused by the molten plastic passing through the mold or gate.
• Sink Marks.
• Vacuum Voids.
• Surface Delamination.
• Weld Line.

How do you prevent sink marks and voids?

Remedies

1. Optimize packing profile. As sink marks occur during packing, the most effective way to reduce or eliminate them is to control the packing pressure correctly.
2. Change the part geometry.
3. Reduce volumetric shrinkage.
4. Relocate gates to problem areas.
5. Optimize the runner system design.
6. Use a different material.

What causes sink injection molding?

Causes: Sink marks are often caused when the cooling time or the cooling mechanism is insufficient for the plastic to fully cool and cure while in the mold. They can also be caused by inadequate pressure in the cavity, or by an excessive temperature at the gate.

What causes porosity in injection molding?

Once the material is injected into the mold cavity, it begins to cool and shrink. This shrinkage can cause voids or porosity to form in the middle of the wall thickness, as the material shrinks towards the mold wall that is causing the cooling.