The gate is the mechanism that allows the plastic resin to flow into the mold, and every plastic part design must take careful consideration of the type and the location of gates. There are various styles of gating mechanisms typically used in injection molding, and each style will have an effect on the finished product. The style of gating chosen can affect the visual appearance of the part, the likelihood of warping or sink marks, and proper packing to meet dimensional tolerances.
Avoid Defects from Gate Location
To avoid defects when processing, place your gate location at the heaviest cross section for maximum fill and packing to avoid sinks and voids. Experienced mold designers will also know when to consider adding a second gate location, which may be necessary in complex geometrical shapes to obtain proper fill throughout the part.
The location of the gate should allow for automatic or manual de-gating, designed with the minimal length of flow path to minimize visual flow marks. In cold runner molds, the part is usually ejected attached to the runner and gate, de-gating removes the part from the runner system. Some processes include automatic de-gating with robotic arms that grab the runner out of the mold separating it from the part or parts.
Gates in Hot-Runner Tools
There are basically two types of gating systems used in hot-runner tools, where the plastic is injected directly into the cavity to avoid runners altogether. In a hot-runner tool, the gate may be either a thermal (or hot-tip) gate, or a valve gate. The hot-tip gate solidifies the resin at the tip nozzle immediately upon high pressure injection into the cavity, stopping the flow of plastic to the cavity.
A valve gate is used when the plastic may not solidify completely upon injection, and therefore a valve slides over to cover the nozzle tip and stop the flow of resin. Either type is effective and cost efficient when used properly in a hot-runner system mold.
Michiana Global Mold is experienced with constructing cold and hot-runner tools, with various styles of gating mechanisms involved. We are skilled with determining the optimum gate location for precision molds required to produce complex geometrical parts.
Michiana Global Mold has been exceeding customer expectation with high performing injection molds since 1964. We have vast experience with all types of molds and mold base components. Contact us today for a FREE design consultation and to speak with one of our knowledgeable design engineers.