Gate dimensions

The cross section of the gate is typically smaller than that of the part runner and the part, so that the part can easily be "de-gated" (separated from the runner) without leaving a visible scar on the part. The gate thickness is typically between one half and two-thirds the part thickness. Since the end of packing can be identified as the time when the material in the gate drops below the freeze temperature, the gate thickness controls the packing time. A larger gate will reduce frictional heating, permit lower velocities, and allow the application of higher packing pressure for a longer period of time. If appearance, low residual stress, and better dimensional stability were required then a larger gate would be advantageous. A minimum size of 0.8 mm is recommended for unreinforced materials. Smaller gates may induce high shear and thus thermal degradation. Reinforced thermoplastics require slightly larger gates > 1 mm. As a rule it should not exceed the runner or sprue diameter. The maximal land length should be 1 mm.