Flow marks result from material's physical properties. The material's flow trace, especially when the filler (including color master) isn't well - dispersed, shows as a visible pattern, like a river's flow, especially in areas with inconsistent thickness.
Adjust Injection Speed: Use multi - stage injection. For uneven - wall - thickness parts, increase speed in thin - wall areas and decrease in thick - wall areas. For common ABS parts, control filling speed at 30 - 50 mm/s.
Control Mold Temperature: Use a mold temperature controller. Different thermoplastics have different optimal mold temperature ranges. For PP, it's 40 - 60 °C; for PC, 80 - 100 °C. Set temperature sensors inside the mold for real - time monitoring.
Optimize Gate Design: Redesign the gate according to part structure and material. Increase gate size to reduce melt flow rate and choose a proper gate location. For flat parts, a side gate in the middle of the length might be suitable.
The material's physical properties, like in modified automotive plastics with base materials and rubber particles, cause a wavy ejective appearance. Strong - elasticity plastics and color - master coloring issues can also lead to this pattern.
Materials: Strictly control material quality, use the same - batch stable materials and conduct random inspections. Optimize additive use and ensure uniform dispersion.
Mold: Optimize the gate by adjusting size and position. Improve the runner by polishing, controlling size, and checking hot - runner heating elements.
Injection Molding Process: Stabilize injection parameters, control speed fluctuation within ±5% with closed - loop control. Use a high - precision temperature controller, especially for complex molds with partition temperature control.
Trapped gas, which differs from gas marks, can't move with the fluid at the end or in corners. Compressed gas raises temperature, causing oxidation and possible burning and yellowing on the product surface. Symptoms include wavy patterns, material shortage, yellowing, and blackening.
Optimize Exhaust System: Check and clean vent holes and slots. Add an exhaust tank (width 0.02 - 0.05 mm, depth 0.01 - 0.03 mm) in gas - trapping areas. Use ventilated steel for better exhaust.
Improve Mold Structure: Simplify complex molds to reduce gas - trapping. Use vacuum exhaust to extract air before injection.
Cold material forms for two main reasons: the front - end material solidifies in the cycle and is pushed by the back - end material, or there are leftover scraps from the last mold (like shovel - glue leftovers, gate wire - drawing scraps, or electrostatic - adsorbed scraps on the parting surface). This causes an illusion of gas marks on the product surface.
Adjust Barrel Temperature: Set each barrel section's temperature according to the plastic material. For cold - material - prone materials like nylon (PA), set the starting temperature at 240 - 260 °C. Ensure a proper temperature gradient for uniform heating.
Optimize Injection Molding Machine Start - up: Before restarting, pre - plasticize to remelt potential cold - material blocks. Set a preheating program to rotate the screw and increase barrel temperature.
Improve Runner System Design: Optimize the flow path by shortening its length and increasing its diameter (e.g., from 3 mm to 4 mm for small parts). Regularly check and maintain hot - runner heating elements.
Shorten Injection Cycle: Optimize injection speed and pressure - holding time. Increase injection speed and adjust pressure - holding time to reduce melt residence time in the runner and gate, especially for thin - wall parts.
