During injection molding process, many factors can affect the quality of plastic injection molding products during injection molding process. Many different deflects of injection molding products may arise, such flash, silver mark, bubble…
Flash （Burr）
Flash refers to excess material in thin layer exceeding normal part geometry of injection molding products. Many reasons can lead to this problem, for example, mold is over packed or parting line on the tool is damaged, too much injection speed/material is injected, clamping force is too low. It can also be caused by dirt and contaminants around tooling surfaces. So we can try to solve this problem by respectively by reducing the amount of plastic injected into cavity, improve the mold parting line, lowering injection pressure, choosing a larger injection machine and cleaning the mold surface.
Voids
A void means empty space within part. The void could happen at any area or part. It is not limited by the thickness but by the resin flow and thermal conductivity, but it is more likely to happen at thicker areas like ribs or bosses of injection molding products.
Lack of holding pressure (holding pressure is used to pack out the part during the holding time) is one of reasons. Too high injection molding speed may also lead to this problem because the plastic filling the cavity too fast, not allowing the edges of the part to form.
Flow Marks (Flow lines)
Flow marks are directionally wavy lines or patterns caused by slow Injection speeds. The plastic has cooled down too much during injection. So injection speeds should be set as fast as is appropriate for the process and material used.
In this passage we talked about Flash, Flow Marks and Voids, more defects of injection molding products will be talked in other passage. Please visit Dakumar for more information.
Edited by Cina Zhu
E-mail: dkm@dakumar.com
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