plastic tooling for automotive product, injection moulding parts, plastic mold manufacture

plastic tooling for automotive product, injection moulding parts, plastic mold manufacture

Service Details:

  • Brand:Kayou
  • Serial Number: M-0178
  • Country of Origin:Shenzhen, China
  • Certificate:ISO9001

Payment & Shipping Terms:

  • Price Quote:Negotiable
  • Minimum Order: 1
  • Average Delivery Time:25 days
  • Payment Method:T/T
  • Package Details:Wooden Case
  • Ability to Supply:5 Set/per month
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plastic tooling for automotive product, injection moulding parts, plastic mold manufacture


plastic tooling for automotive product, injection moulding parts, plastic mold manufacture

Formation and types of weld marks

Formation of weld marks

When the injection products are processed, the melt flows from the gate to the cavity. When there are multiple streams of material flow, these streams will converge in the cavity. When they converge, the weld lines will inevitably occur when they are combined in a linear or non-point form. The formation of multi-strand material flow is generally caused by the following circumstances: the use of multi-gate structure on the die, or with holes and inserts on the parts. The weld joints are generally three-dimensional structures, and their effects on the appearance and properties of the parts depend on the weld condition.

Types of weld marks

There are two kinds of most common weld marks: the weld marks formed at the beginning of filling, called early weld marks. At the end of filling, the two strands are finally joined, and the weld marks formed are called post-weld marks. The weld marks can also be divided into cold and hot weld marks. The weld marks around the inserts are cold weld marks.

Through the study of various weld marks, it is found that the line and point weld marks of injection products are in fact a three-dimensional region. The properties of the weld zone are lower than those of other parts of the products. The structure and shape of the weld zone determine its properties.

Structure and Morphology of Welding Zone

Assuming that the two streams belong to steady state flow, the weld line will be formed. Because the melt adheres to the cavity wall seriously, the melt will flow from the center of the wavefront to the cavity wall when filling, which will make the melt flow in the front of the melt flow orientate in one direction. The melt zone must contain many orientated molecules perpendicular to the flow direction. When air is entrapped, bubbles or grooves form on the surface when two or more wavefronts are concentrated. From the microscopic point of view, the aggregation state of molecule in the fusion zone is quite different from that in other regions.

For crystalline plastics, the melting zone is more complex. Besides molecular orientation, it is also related to crystallinity, spherulite size and cooling rate. Slow cooling is conducive to the formation of crystals, spherulites become larger and larger, crystallinity is higher; rapid cooling is conducive to the formation of nuclei, spherulites are smaller, crystallinity is low, spherulites micro-distribution is uniform, amorphous areas are more.

Influencing factors of weld marks

Structural Patterns of Polymers

It is very important to improve the strength of weld marks because of the low strength of weld marks produced by injection products. There are many factors affecting the strength of weld marks, such as injection molding process conditions, the number and location of gate, whether there are cold material holes near the weld marks and the wall thickness of products, etc. More importantly, the structure and morphology of polymer are more important. The effect of structure morphology on the strength of weld marks is mainly manifested in crystallization and non-crystallization, as well as the presence or absence of orientation structure or degree of orientation.



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plastic tooling for automotive product, injection moulding parts, plastic mold manufacture


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