Do you know the five ways to avoid injection weld marks?

When the molten plastic meets in the mold cavity in the form of multiple strands due to inserts, holes, areas with discontinuous flow rate, areas with interrupted filling material flow, and when the gate injection filling occurs, linear weld marks will be produced due to incomplete fusion. The existence of weld marks has greatly weakened the mechanical strength of products. The method to overcome the weld mark is basically the same as the method to reduce the product depression.
1、 Equipment
Poor plasticization and uneven melt temperature can prolong the molding cycle and make the plasticization more complete. If necessary, replace the machine with large plasticization capacity.
2、 Mold
(1) If the mold temperature is too low, the mold temperature should be appropriately increased or the local temperature at the fusion joint should be purposely increased.
(2) The flow path is small, too narrow or too shallow, and the cold well is small. The size of the flow channel should be increased to improve the efficiency of the flow channel, and the volume of the cold material well should be increased at the same time.
(3) Enlarge or reduce the gate section and change the gate position. When opening the gate, try to avoid the melt flowing around the insert and hole. Try to correct, migrate or add stop buffer for the gate with injection mold filling. Try not to use more gates or less.
(4) Poor exhaust or no exhaust hole. The exhaust channel shall be opened, expanded or dredged, including the use of inserts and ejector pin gaps for exhaust.
3、 Process
(1) Increase injection pressure and prolong injection time.
(2) Adjust the injection speed: high speed can make the molten material reach the confluence without cooling down, and low speed can make the air in the mold cavity have time to exhaust.
(3) Adjust the temperature of the barrel and nozzle: high temperature, low viscosity of plastic, smooth flow pattern, and thin weld line; Low temperature reduces the decomposition of gaseous substances.
(4) The release agent should be used as little as possible, especially the release agent containing silicon, otherwise the material flow cannot be fused.
(5) Reduce the clamping force to facilitate exhaust.
(6) Increase the screw speed to reduce the plastic viscosity; Increase the back pressure to increase the density of plastics.
4、 Raw materials
(1) The raw materials should be dry and the liquid additives in the formula should be minimized.
(2) Lubricants and stabilizers shall be properly added to plastics with poor fluidity or high heat sensitivity, and plastics with good fluidity or high heat resistance shall be used when necessary.
5、 Product design
(1) The wall thickness is small, so the parts should be thickened to avoid premature curing.
(2) If the position of the insert is incorrect, it should be adjusted.