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Hand lay-up method defect,reason and solution

Oct 25, 2018

1.Gel coat defects: three common defects are wrinkle, crack and discoloration


 Causes and prevention methods of corrugation of gel coat

 Prevention methods


The coating is too thin

Spray resin should reach 500-600 g/m2


Inadequate initiator and promoter dosage

Adjust dosage according to different temperature and humidity

The residual styrene in the moldThe residual styrene monomer is blown out with a blower
The temperature is too low

Air blast or heat with infrared light


If the gel coat is not curing enough, it will start to pasteCorrectly judge the curing state and determine the timing of paste
Uneven gel coat

Brush and spray the product equally



hand lay-up defect


 The cause and prevention of the chafing crack of gel coat

 Prevention methods


Too much initiator and promoter

Adjust the dosage


Too much heat during curing

Adjust the heating temperature and curing in


Intense sunlight

Avoid strong sunlight when curing


Gel coat is too thick

Brush and spray the product equally



hand lay-up hand lay up

hand lay up


2. Product shrinkage: some parts of corner or slope surface (gel coat), sometimes separated from mold, overhead or depression, this defect is called shrinkage.


 Causes and prevention of shrinkage

 Prevention methods


Curvature radius R is too small around the corner

Adjust the radius of curvature to big


It is not easy to separate the gel coat from the mold when stripping

Use the mold 2 to 3 times and brush the mold release agent once


local thickness of product is too greatThe reinforcing material is laid in a staggered and overlapping position.Keep the corners from gathering
The content of roving in small radius of curvature is excessive

Control roving amount.When impregnating, remove excess resin


Uneven gel coatThere shouldn't be too much gel coat around the corner.Avoid local overheating.The dosage of curing agent is appropriate





3.Warping and deformation



Prevention methods



Resin curing shrinkage of large, over - addition of styrene

Add filling in moderate amounts,control the amount of styrene added


Excessive amount of initiator and promoter

Initiator and promoter should be added in appropriate amount


thickness of product is too thin

Add strong tendons to the flexible part



thickness of product is uneven or asymmetrical

Product design should avoid wide wall thickness, wall thickness uniform


The resin accumulation

Resin viscosity hour, should prevent low concave or groove where the glue liquid accumulation


The treatment time after heating is not appropriate

After forming the wall thickness product, place it for a period of time and heat it up


Heat treatment is not uniform in temperature

The mold should be uniformly heated to avoid putting it near the hot air vent


Premature release and incomplete cureProducts shall be solidified to a certain extent before demoulding, to determine the appropriate time of demoulding