TROUBLESHOOTING

Jetting occurs when the melt flow exiting the gate or other restrictive area enters a mold cavity and does not come in contact with the mold wall or some type of impingement. The abrupt drop in pressure creates a disorganized, higher viscosity flow into the open cavity. Snake-like tracks will appear across a part. This effect is actually a result of multiple miniature weld lines where the melt folds over itself. Apart from a poor finish, it will also create part weakness.

Mold Design
A gate design that encourages melt flow to travel towards a wall or a pin instead of into a free, unrestricted area is preferred.

• Leave a maximum impingement distance of 6.35 mm (0.25") between a gate and the opposing wall
• If this is not possible, changing the angle of the gate to increase the impingement of the melt flow along the mold wall may be an option
• Installing a pin just before the gate or a spring-loaded pin just after the gate may help to disperse material along the mold wall

It is, however, always recommended to have a gate location that maximizes melt-to-mold contact in the beginning. It is possible that jetting will only be reduced by changing the location of the gate.

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