Tooling/mould making service, plastic injection mold

Tooling/mould making service, plastic injection mold

Service Details:

  • Brand:Kayou
  • Serial Number: M-0150
  • 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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Tooling/mould making service, plastic injection mold


Tooling/mould making service, plastic injection mold

Source of Gas in Injection Mold

Air in pouring system and mould cavity

Some raw materials contain moisture that has not been dried out, and they are gasified into steam at high temperatures. Gases produced by the decomposition of some unstable plastics due to the high temperature during injection moulding. Gases produced by volatilization or chemical reactions of some additives in plastics raw materials.

Harm of bad exhaust

Poor exhaust of injection moulds will bring a series of hazards to the quality of plastic parts and other aspects. The main performances are as follows:

In the process of injection moulding, the melt will replace the gas in the cavity. If the gas is not discharged in time, it will cause difficulty in filling the melt, resulting in insufficient injection volume and not filling the cavity.

Removal of unobstructed gas will form high pressure in the cavity and infiltrate into the plastic under certain degree of compression, resulting in porosity, voids, loose tissue, craze and other quality defects.

Because the gas is highly compressed, the temperature in the cavity rises sharply, which causes melt decomposition and burning around, resulting in local carbonization and charring of the plastic parts. It mainly occurs at the confluence, angle and gate flange of the two melts.

The gas is not removed smoothly, which makes the melt velocity into each cavity different, so it is easy to form flow marks and fusion marks, and reduce the mechanical properties of plastic parts.

Because of the obstruction of gas in the cavity, the filling speed will be reduced, the forming cycle will be affected, and the production efficiency will be reduced.

Bubble Distribution in Plastic Parts

The gas sources in the cavity are mainly divided into three categories: the air accumulated in the cavity; the gas generated by the decomposition of the raw materials; the water vapor evaporated from the residual water in the raw materials, and the positions of the bubbles produced by the different sources are also different.

The bubbles generated by the accumulated air in the die cavity are often distributed in the position opposite to the gate.

The bubbles produced by decomposition or chemical reaction in plastic raw materials are distributed along the thickness of plastic parts.

The air bubbles generated by residual water vaporization in plastic raw materials are irregularly distributed throughout the plastic parts. From the distribution of bubbles in the plastic parts mentioned above, not only the properties of bubbles can be judged, but also whether the exhaust parts of the mould are correct and reliable.

Function and Structure of Die Exhaust

Function of exhaust

In the process of filling the injection cavity with plastic melt, besides the original air, there are water contained in the cavity, low molecular weight substances and gases produced by melt decomposition during heating, volatiles of plastic additives and so on. If these gases are not discharged from the cavity during injection, they will affect the quality of the product after moulding and demoulding. If these gases are involved in the melt during the filling process, the bad phenomena such as bubbles will occur in the core part of the plastic parts, which will seriously affect the quality of the plastic parts. In addition, the high pressure and high temperature effect of these gases often causes partial carbonization and charring of the products. Therefore, while designing the die cavity, we must consider setting up the exhaust structure to ensure that the product does not have quality problems due to bad exhaust.



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Tooling/mould making service, plastic injection mold


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