When injection molding large products, molding is usually performed with multi-point gates, but weld lines can occur depending on the product shape and gate position.
Weld lines may occur depending on the product shape and gate positions. The more gate points there are, the more weld lines will occur. If the large molded product is an exterior part, weld lines will be noticeable even if it is painted, which is NG.
However, if the mold is heated and cooled as in heat & cool, the molding cycle becomes very long and unproductive.
In such a case, it is possible to set the multi-point gate to a relay gate setting to eliminate or make the weld lines less noticeable.
(In a normal multi-point gate, valves are opened and closed at the same time, so the flow tips collide with each other, resulting in weld lines.
Therefore, the valve opening timing is intentionally delayed.
This allows the resin to flow in a manner that merges with the first resin flow, thus eliminating or disguising weld lines.
It is also called a relay gate because it looks like a relay race, with the second runner running at the same time as the first runner finishes running.
Naturally, there are cases where the above does not work due to the shape of the product, the number of gate points, or their arrangement.
In such cases, CAEn flow analysis can be performed in advance to predict where weld lines will occur and when valves will open.
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