HOW TO AVOID WELDING LINES WHILE INJECTION MOLDING?

I. Rquipment

Poor plasticization and uneven melt temperature can extend the molding cycle, make plasticization more complete, and replace the machine with large plasticization capacity if necessary.

II. 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 purposefully increased.

(2) The flow channel is small, too narrow or too shallow, and the cold feed well is small. The size of the runner should be increased, the efficiency of the runner should be improved, and the volume of the cold feed well should be increased.

(3) Expand or reduce the gate section and change the gate position. The gate should be opened to avoid the flow of melt around the insert and hole as much as possible. The gate where jet filling occurs should be corrected, moved or cushioned with a block. Try not to use more or less gate.

(4) Poor exhaust or no exhaust holes. Exhaust channels shall be opened, expanded or dredged, including the use of inserts and thimble gaps for exhaust.

III. The process

(1) Increase the injection pressure and prolong the injection time.

(2) Adjust the injection speed: high speed can make the melt reach the junction without time to cool down, and low speed can allow the air in the cavity to have time to discharge.

(3) Adjust the temperature of the barrel and nozzle: the viscosity of the plastic with high temperature is small, the flow is smooth, and the welding mark is thinner; Low temperature reduces decomposition of gaseous substances.

(4) Release agents should be used as little as possible, especially silicon-containing release agents, otherwise the material flow can not be fused.

(5) Reduce the clamping force to facilitate the exhaust.

(6) Increase the screw speed to reduce the plastic viscosity; Increase the back pressure to increase the density of plastic.

IV. Raw materials

(1) Raw materials should be dried and liquid additives in the formula should be minimized.

(2) Add lubricants and stabilizers appropriately to plastics with poor fluidity or high heat sensitivity, and use plastics with good fluidity or high heat resistance if necessary.

V. Product design

(1) The wall thickness is small, and the parts should be thickened to avoid premature curing.

(2) Improper insertion position should be adjusted.