1 . The plastic part is not enough : mainly due to insufficient feeding , poor melt filling flow , excessive inflation and poor exhaust gas , the filling cavity is not filled with dissatisfaction , the plastic part is incomplete in appearance , and the individual cavity is filled with dissatisfaction when the shape of the plastic part is incomplete or multiple cavities .

2 . Dimensional instability : due to poor die strength , poor accuracy , unstable injection machine , unstable forming conditions , etc . , the dimensional change of the plastic part is not stable .

3 . Bubble : resulting in residual gas in the plastic part due to excessive inflation or poor exhaust gas in the melt , and a small volume or string of holes ( note that it should be distinguished from the vacuum bubble )

4 . Collapse pits ( dents ) or vacuum bubbles : due to poor pressure maintaining and feeding , uneven cooling of the plastic parts , uneven wall thickness and large plastic shrinkage

5 . Too large flying edge : due to poor mold closing , excessive clearance , too good plastic fluidity , excessive feeding of plastic parts along the edge

6 . Poor fusion : due to the low material temperature , the insolubility of the resin and the attachments when the melt is split and combined , the fusion material is not melted at the time of convergence , and obvious fine - connecting suture is generated along the surface or the inside of the plastic part .

7 . Surface ripple of plastic parts : because the molten material is not regular flow filling the cavity along the surface of the mold , it is a semi - solidified wave shape , and the flow or melt of the molten material has a stagnation phenomenon .

8 . Poor demoulding : due to the excessive filling effect , poor mold release performance , etc . , the plastic parts are difficult to be demoulded or the plastic parts after demoulding are deformed , cracked , or the residual direction of the plastic parts does not meet the design requirements .

9 . The mica sheet - like layered peeling : because the mixture is mixed with the different materials or the mold temperature is low , the shearing action is too large when the molten material flows along the surface of the mold , so that the material is exfoliated and the physical property is reduced .

10 . Gate sticking die : due to mechanical resistance in the sprue bushing , insufficient cooling or failure of the pull rod , the gate is stuck in the sprue bushing .

11 . Poor transparency : due to poor contact between the melt and the surface of the mould , the surface of the plastic part has fine pits which cause the ray to be disturbed by radiation or plastic decomposition , foreign matter impurities , or the surface of the mould is not bright , so that the transparency of the transparent plastic is bad or uneven .

12 . Silver streak : Due to excessive moisture or inflation in the material and excessive volatile matter , the melt is subjected to shearing action too large , and the melt material and the surface of the mold are not in close contact with each other , or the mixture is rapidly cooled or mixed with different materials or decomposed and deteriorated , so that the surface of the plastic part has silver - white glossy needle - like stripes or mica sheet - like stripes along the direction of the material flow .

13 . Warping and deformation : due to residual stress , shear stress , cooling stress and uneven shrinkage during forming , internal stress is caused ;

Poor demoulding , insufficient cooling , insufficient strength of the plastic part , deformation of the mould and the like , so that the deformation of the plastic part is distorted , the warpage is uneven or the type hole is offset , and the wall thickness is not uniform and the like .

14 . cracks : due to excessive internal stress of the plastic part , poor demoulding , uneven cooling , poor plastic property or poor design of the plastic part and other defects ( such as deformation ) , the surface of the plastic part and the vicinity of the feeding port are caused to be fine cracks , or cracking or cracking or the like does not occur in the load and the solvent .

15 . Black point , black bar : Decomposition and combustion of combustible volatile matter , air , etc . under high temperature and high pressure due to plastic decomposition or material , combustible material injected into the plastic cavity with melt , black spots on the surface of the plastic part , black stripes , or carbon - like burns along the surface of the plastic part .

16 . The color unevenness or discoloration : due to poor distribution of pigment or filler , the color of the plastic or pigment is uneven on the surface of the plastic part . The color unevenness follows the phenomenon that the color of the plastic part is uneven . When the color of the part is not uniform , the pigment distribution is not uniform . When the color of the whole part is uneven , the color of the welding part is not uniform . When the color of the welding part is uneven , all of these are related to the properties of the pigment .