Reasons why injection molding is difficult to demold

author: Universe plastic

2024-04-06

After injection molding of plastic parts, the plastic parts are ejected from the mold cavity. Whether a single or multi-element ejection mechanism is used, the demoulding work is generally completed at one time.

However, sometimes due to the special shape of the plastic part or the need for production automation, after the demoulding work is completed, the plastic part is still difficult to take out from the mold cavity or cannot automatically fall off. At this time, another demoulding action must be added to make the plastic part fall off.

Difficulty in demoulding is mainly due to the gate or plastic part being tightened in the mold. The reasons include:

Mold design issues

Grooves inside the mold, insufficient draft angle, low mold finish, unreasonable demoulding structure or improper position may lead to difficulty in demoulding.

Process parameter issues

Too high injection pressure, too long pressure holding time, insufficient cooling time, inappropriate mold temperature, etc. may cause difficulty in demoulding.

Raw material issues

Difficulties in demolding may be caused by impurities being mixed into raw materials during packaging and transportation, raw materials of different grades being mixed into during pre-drying and preheating, and foreign matter being mixed into barrels and hoppers.

Improper use of release agent

Improper selection and use of release agents may also affect the release effect.

Poor mold cooling and exhaust

Insufficient cooling of the mold or unreasonable exhaust design may lead to difficulty in demoulding.

The ejection mechanism is unreasonably designed or improperly operated.

Insufficient ejection force, insufficient ejection stroke, poor ejection plate movement, etc. may lead to difficulty in demolding.

Methods to solve demoulding difficulties include optimizing mold design, adjusting process parameters, selecting appropriate raw materials, correctly using release agents, improving mold cooling and exhaust design, and rationally designing ejection mechanisms, etc.

In actual operation, it may be necessary to consider multiple factors and make corresponding adjustments.

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