What are the defects of silicone products?

The thickness of the product is uneven, the outer dimensions are out of tolerance, and the dimensions do not meet the drawing requirements.

Causes:

1. Poor parallelism of equipment and molds

2. Silicone shrinkage calculation is inaccurate

3． Poor mold processing

2. Lack of glue

Waste characteristics:

The product has no obvious outline and its shape does not meet the requirements of the drawing.

The product has a clear outline, but there are local depressions and defects.

Causes:

1. The weight of the compound loaded is insufficient.

2. The rise is too fast during pressing, and the rubber material does not fill the cavity and overflows out of the mold.

3． Poor exhaust conditions

3. Flash thickening

Characteristics of waste products: Silicone rubber products have thickening at the parting surface of the mold.

Causes:

1. The amount of glue loaded is too much

2. The mold does not have the necessary remaining material chute or the remaining material chute is too small.

3． Not enough pressure

4. Bubbles

Characteristics of waste products: There are bubbles on the surface and inside of silicone rubber products.

Causes:

1. Not all the air in the cavity is exhausted during pressing

2. The rubber contains a large amount of moisture or volatile substances

3． Poor mold exhaust conditions

4. The weight of the glue loaded is not enough

5. Concave and concave defects

Characteristics of waste products: There are convex and concave marks on the surface of silicone rubber products

Causes:

1. Processing marks left during mold processing

2. The rubber material itself is defective (such as high viscosity or expired)

3． Poor mold exhaust conditions

6. Crack

Characteristics of waste products: There are cracks on silicone products

Causes:

1. When taking out the product and opening the mold, the product was scratched

2. Material layering occurs due to the excessive application of isolating agents in the cavity.

3． Mold structure is unreasonable

4. The rubber molding method is unreasonable (especially fluorine rubber and high-hardness nitrile rubber)

7. Wrinkles, cracks and separation layers

Characteristics of waste products: wrinkles on the surface of the product, cracks, and delamination on the surface and inside of the product

Causes:

1. Dirty rubber material is loaded into the cavity

2. Too much release agent applied in the cavity

3． Mixing different rubber materials

4. Process operations (forming, feeding methods) are incorrect

5. Rubber material expired

8. Impurities

Characteristics of waste products: There are impurities on the surface and inside of the product.

Causes:

1. The rubber compound is mixed with impurities during plasticizing, mixing, storage and transportation.

2. The mold is not cleaned (including flash edges and waste material)

9. Parting surface misalignment

Scrap type: The product has a large misalignment at the parting surface

Causes:

1. Mold manufacturing accuracy error and insufficient processing accuracy

2. The 45-degree parting rubber ring is thickened due to flash.

3． Poor mold positioning

10. Curling

Characteristics of scrap products: The product has obvious inward shrinkage at the parting point.

Causes:

1. Poor rubber processing performance (such as fluorine rubber)

2. The mold structure is unreasonable (thick products should use closed structure molds and reasonably open residual material troughs)