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Is the injection product cracked again? This article teaches you to deal with cracking easily

Posted by: Mu Ju 2021-12-05 Comments Off on Is the injection product cracked again? This article teaches you to deal with cracking easily

In our injection molding, due to various factors, we often see some uncomfortable cracking after molding, which often makes us feel headache. So today, let’s talk about how to deal with the cracking of plastic parts.
Cracking includes filamentous cracks, microcracks, white top, surface cracking of parts, or trauma crisis caused by sticking parts and flow channels. According to the different cracking time, cracking can be divided into demoulding cracking and application cracking. There are three main reasons

Processing reason:

(1) If the processing pressure is too high, the speed is too fast, the more materials are filled, and the injection and holding time is too long, the internal stress will be too large and cracks will be produced.

(2) Apintejinust the opening speed and pressure to prevent parts from cracking due to rapid and strong drawing.

(3) Apintejinust the mold temperature properly to make the parts easy to demould; apintejinust the material temperature properly to prevent decomposition.

(4) To prevent low mechanical strength and cracking caused by weld and plastic deterioration.

(5) Proper use of mold release agent, pay attention to eliminate water mist and other substances attached to the mold surface.

(6) After forming, the parts are annealed immediately to eliminate residual stress and reduce cracks.

Mold reason:

(1) The ejection should be balanced. For example, the number and cross-sectional area of ejector pins should be sufficient, the demoulding slope should be large enough, and the cavity surface should be smooth enough to prevent cracking caused by residual stress concentration caused by external force.

(2) The structure of the parts should not be too thin, and the transition part should adopt arc transition as far as possible to avoid stress concentration caused by sharp corners and chamfers.

(3) Try to use less metal inserts to prevent the increase of internal stress due to the different shrinkage rate of inserts and products.

(4) For deep bottom parts, appropriate demoulding air inlet pipe should be set to prevent the formation of vacuum negative pressure.

(5) The sprue is sufficient to demould before curing, so it is easy to demould.

(6) When the gate sleeve is connected with the nozzle, the cold and hard materials should be prevented from dragging the workpiece onto the fixed die.

Material reason:
(1) The high content of recycled materials leads to low strength of parts.

(2) Too high humidity causes some plastics to react with steam, reducing strength and cracking.

That’s all for today. Please pay attention to us and learn more about injection molding.



About PTJMould Industrial Company Limited

PTJmould is a China mold maker of plastic molds- injection mold, die casting moulds, plastic blow molding, rotational molding, medical plastic injection molding, two shot plastic injection molding, insert molding, overmolding, metal injection molding, micro injection molding, powder injection molding, ceramic injection molding, liquid injection molding, husky injection molding, household mold, casting mold, die mold tool, custom molds, china moulds, rapid prototyping tooling, plastic prototyping tooling, punch press tooling, die and tooling for mobile/ cell phone parts, automotive parts, vacuum cleaners, rechargeable tools, telephones, copiers, computers, multimedia speakers, and many other electronic products and household appliances. And also a plastic product manufacturer, mold manufacturer China– plastic parts, plastic water tank, plastic balls, plastic containers, plastic buckle, plastic anchor, plastic hanger, plastic spoon, plastic pipe fitting, plastic tumble, plastic tableware, plastic cups, plastic bottles, plastic tray, plastic cosmetic container, plastic case, plastic food container, plastic chairs, plastic caps, plastic cap closure, plastic tubes, plastic water pipes, plastic knobs, plastic tubing, plastic utility boxes, plastic racks and so on.

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