Production problems and solutions(1)

Lack of material

Lack of material is also called short shot, broken shot, insufficient filling, etc., so that in the production process of injection molded parts, the plastic melt cannot completely fill the molding space of the mold after entering the cavity.
Common causes and solutions from

Improve methods

Increase barrel temperature

Increase injection pressure or clean condenser

Increase metering stroke

Increase the injection time or delay the switch to hold pressure

Speed up injection

Reopen the mold transportation channel

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Appropriate position plus moderate exhaust groove/needle

Remove/clean the nozzle or re-spray

Reset the gate/or adjust the balance

Increase runner/gate size or shorten runner

Add lubricants as appropriate (improve fluidity)

Remove the non-return ring and repair or replace

Replace larger machines or check/improve the cutting conditions

Improve the thickness or thickening of the plastic parts

Switch to plastic with better fluidity


During the production and molding process of injection molded parts, due to insufficient pressure in certain positions of the mold cavity, when the melt begins to cool, the volume shrinkage of the larger wall thickness of the plastic part is slower and tensile stress is formed. If the surface hardness of the product is not enough , And there is no melt supplement, the surface of the product will be strained by stress. This phenomenon is called shrinkage

The specific reasons and improvement methods are as follows

Enhanced melt injection volume

Increase the melt metering stroke

Increase injection pressure

Increase the holding pressure or extend the holding time

Extend injection time (using pre-ejection action)

Speed up the injection speed or slow down the injection speed

Increase the gate size or balance the mold injection

Remove and clean foreign objects in the nozzle or replace the heating coil

Re-align/tighten nozzle or reduce back pressure

Adjust material temperature (appropriate)

Increase mold temperature or appropriately reduce mold temperature

Extend the cooling time as appropriate

Open an exhaust slot at the shrinkage area

Make the glue thickness as uniform as possible (change to gas-assisted injection molding)

Removal and replacement of non-return ring (over apron)

The gate is opened at the wall thickness or the number of gates is increased

Bold main/division runner, reduce runner length

Called flash

In the production of injection molded parts, the phenomenon that plastic melt is squeezed from the parting surface of the mold and produces flakes on the edge of the product is called flash, commonly known as batch front

The specific reasons and improvement methods are as follows

Reduce melt temperature and mold temperature

Reduce injection pressure or reduce injection speed

Decrease holding pressure

Repair mold or improve mold clamping accuracy

Increase clamping force

Replace the machine with larger clamping force

Rebalance the gate

The mold is equipped with a support head or the mold hardness is increased

Switch from injection to pressure holding position early

Choose better steel and heat treatment

Use plastic with higher viscosity or add filler

Clean up foreign objects on the mold surface or repair/replace the hinge