1) Snake flow texture - When melt enters mold cavity from gate, a jet effect is generated and appears on the surface of product like a snake, so it is called snake flow texture.
2) Wave texture - Melt flows unsteadily in mold cavity, sometimes fast and sometimes slowly, and appears like waves on the surface of product, so it is called wandering texture.
3) Radial textures - generally only appear near gate. When melt enters mold cavity, a jet is generated, which appears as a radial texture on the surface of product, so it is called radial textures.
4) Fluorescent streaks - Shear stress generated by melt flow causes surface of product to produce a luster that is very similar to body of a firefly, so it is called fluorescent streaks.
Solution to flow texture:

When gate depth is much smaller than mold cavity entrance depth, and mold filling rate is very high, melt flow becomes an unstable jet flow. Front jet has solidified and flowing melt behind has filled mold cavity. At this time, snake flow textures will appear on the surface of product.
Solution:
① Change process conditions. Using method of reducing injection rate will gradually eliminate jet effect and expand melt flow. Expanded flow will make product have better surface quality. In addition, increasing mold temperature and melt temperature will also reduce jet effect and expand melt flow.
②Change mold gate size. When gate depth is slightly smaller than mold cavity depth, exit expansion of jet causes melt at the back to merge with front edge of jet that flows out not far from the front, so that jet effect is not obvious. When gate depth is equal to or close to mold cavity depth, mold filling rate is low and an expanding flow is formed.  
③Change mold gate angle. Make angle between mold gate and movable mold 40 to 50, so that when melt flows out of gate, it will first be blocked by mold cavity wall, which can prevent occurrence of snake flow lines.
④Change mold gate position. Set mold gate at the closest position to mold cavity wall (perpendicular to direction of gate). When melt flows out of gate, it will first be blocked by cavity wall, which can also prevent jet from appearing and make it an expanded flow, thus avoiding appearance of snake flow textures.

During melt filling process, new melt flow is continuously pressed out from inner layer, pushing the front wave to move stagnantly. At the same time, edge of front wave is continuously stretched. Due to flow resistance, melt pressure rises later and flattens previously formed ripples forward, causing stagnant accumulation and thus forming wavy patterns on the surface of product. Especially when injection rate is fast, injection pressure is low, or mold structure is unreasonable, melt flow advances and stops, PP crystallizes quickly and slowly, which is more likely to cause inconsistent crystallinity on the surface of product and form wavy lines on the surface of product.
Solution:
① Change process conditions. Use of high-pressure and low-speed injection can maintain stability of melt flow and prevent appearance of ripples.
② Increase mold temperature. As mold temperature increases, melt fluidity increases. For crystalline polymers, higher temperatures are beneficial to uniformity of crystallization, thereby reducing appearance of wavy lines.
③Change mold cavity structure. Structure of mold can also cause wavy textures on the surface of product. If mold core has prominent edges and corners, melt flow resistance will be large, which will cause melt flow to be unstable and form wavy textures. Therefore, changing edges and corners of mold core allows it to buffer transition, maintain stable melt flow, and prevent appearance of wavy lines.
④Change thickness of product. Uneven thickness of product will cause melt flow resistance to vary from time to time, causing melt flow to be unstable. Therefore, try to design product thickness to be uniform to prevent appearance of wavy lines.

When injection rate is too large and melt is ejected, due to elasticity of melt, when melt flows rapidly from barrel through mold gate to mold cavity, elastic recovery of melt is too fast, causing melt to rupture and produce radial marks.
Solution:
① Change process conditions. Using high-pressure and low-speed injection can increase flow time of elastic melt over same flow length and increase degree of elastic failure, thereby reducing appearance of radial lines.
② Change mold gate shape. Enlarging gate or changing gate to a fan shape can slightly restore elasticity of melt before entering mold cavity to avoid melt rupture.
③ Extend length of main runner of mold. Before melt enters mold cavity, its elasticity fails first to avoid melt rupture.
④Replace equipment with an extension nozzle. Lengthening flow path of melt before entering mold cavity increases elastic failure of melt and avoids radial marks due to melt rupture.

When melt flows in mold cavity, one end of molecular chain close to solidified layer is fixed on solidified layer, while the other end is stretched along flow direction by adjacent molecular chains.
Since flow resistance of melt near wall of mold cavity is the largest and flow rate is the smallest, while flow resistance at the center of mold cavity is the smallest and flow rate is the largest, a velocity gradient is formed in flow direction. Therefore, when injection rate is small and injection pressure is high, a velocity gradient is formed. Or when product is thin, melt near mold cavity wall has the strongest shear force and the greatest orientation. Polymer is stretched during flow and exhibits internal stress, causing fluorescent textures to appear on the surface of product.
Solution:
① Change process conditions. Using medium-pressure and medium-speed injection, as injection rate increases, cooling time of melt decreases on same runner length, and solidification of melt per unit volume becomes relatively slow, which weakens internal stress of product and reduces appearance of fluorescent streaks on the surface of product.
② Increase mold temperature. A higher mold temperature can accelerate relaxation of macromolecules, reduce molecular orientation and internal stress, thereby reducing appearance of fluorescent textures on the surface of product.
③ Change mold cavity structure and increase thickness of product. Thickness of product is larger, melt cooling is slower, stress relaxation time is relatively longer, and orientation stress will be reduced, thereby reducing fluorescent streaks.
④ Heat treatment (oven baking or hot water boiling). Heat treatment intensifies movement of macromolecules, shortens relaxation time, and strengthens deorientation effect, thus reducing fluorescent streaks.