Plastic tool for mechanical parts, injection moulding making service

Plastic tool for mechanical parts, injection moulding making service

Service Details:

  • Brand:Kayou
  • Serial Number: M-0187
  • 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 tool for mechanical parts, injection moulding making service

Description

Plastic tool for mechanical parts, injection moulding making service

Under injection moulding conditions, the strength of amorphous plastics at weld marks is relatively low. For example, the tensile strength at weld marks is 0.87-0.95 and 0.73 for semi-crystalline high density polyethylene and semi-crystalline polypropylene, respectively, compared with the tensile strength in orientation direction. For non-crystalline plexiglass, polystyrene, ABS and AS, the values can only be 0.30-0.37, 0.6-0.8 and 0.15, respectively. And so on. In terms of impact toughness alone, the impact toughness of weld lines is often greater than that of other parts, which is due to the effect of orientation. Generally speaking, when plastic melts with different flow directions converge, they not only have no orientation effect, but also destroy the existing orientation structure in each strand of melt, so the macromolecule appears random cluster at the weld mark, and the impact toughness appears higher. However, if the orientation effect is not alleviated, the impact toughness at the weld mark will be lower.

Injection process parameters

Melt temperature. The strength of weld marks of injection moulded products is largely determined by the number of molecule entanglements in the material flow front, which requires large molecular fluidity. With the increase of thermal motion of molecules, the degree of entanglement is higher and the entanglement rate increases.

Mold temperature. High die temperature can avoid rapid melt cooling, which can maintain high molecular fluidity during the forming cycle, and compensate for the rapid cooling of melt wavefront by runner and cavity. It is advantageous for more entanglement of macromolecule to improve the strength of weld mark, but it is different for crystalline plastics. High mould temperature, high crystallinity, mechanical properties have a greater impact.

Injection speed. When the resin with low melt flow rate (MFR) is used for injection, the strength of weld marks increases with the increase of injection rate. For the resin with low MFR, the increase of injection rate has little effect on the weld strength.

Cooling time. Cooling time, on the one hand, is related to cooling rate, on the other hand, it is related to product finalization, which has an impact on weld line strength, but it is not very large.

With the increase of the thickness of the product and the position of the gate, the weld strength will be improved. As the thickness of the product increases, the contact area of the fusion zone increases, so the fusion strength increases. The location of the small gate determines the area and position of the weld line. Therefore, the location of the gate in a relatively short flow distance can enhance the strength of the weld line.

Measures to Eliminate or Reduce Weld Marks

In addition to affecting the strength of products, weld marks also affect the surface quality of products. In order to eliminate or mitigate the defects of weld marks, the following measures are listed.

Reasonable selection of gate location and gate size

The position of weld mark is related to the shape of the product and the position of the gate. Therefore, if necessary, the position and size of the gate should be changed to adjust the position and influence of the weld line.

Improving the Exhaust Function of Die

When filling the plastic melt, the air in the die cavity must be removed. If air is mixed in the melting zone, the burns will occur slightly, but the heavy ones will not be fully fused. Therefore, the exhaust function of the die cavity must be guaranteed. Some of the exhaust moulds rely on the structure of block, ejector rod, and sometimes need to set up a special exhaust groove to exhaust.

 

 

 

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Plastic tool for mechanical parts, injection moulding making service

 

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FAX :
86-7552-3156569
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Factory Address :
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