During injection molding process, many factors can affect the quality of plastic products during injection molding process. Many different deflects of injection molding products may arise, such flash, silver mark, bubble…
In another passage we have talked about Flash, Flow Marks and Voids, in this passage we will talk about Warping, Weld line, Silver marks.

Warping (Twisting)
Warping is the distorted part caused by too short cooling time, too hot material, a lack of cooling around the tool, incorrect water temperatures (the parts inwards towards the hot side of the tool) and uneven shrinking between areas of the part in injection molding process. We can avoid warping respectively by lengthening holding time, reducing material temperature……

Weld line（Knit line / Meld line / Transfer line）
Weld line is discolored line where two flow fronts meet. Reasons cause weld line may be too low mold/material temperature during injection molding (the material is cold when they meet, so they don't bond). Weld line can be minimized or eliminated with a mold-flow study when the mold is in design phase. Once the mold is made and the gate is placed, one can minimize this flaw only by changing the melt and the mold temperature during injection molding process.

Silver marks (Splash mark / Silver streaks)
Silver marks means circular pattern around gate caused by hot gas because there exists some moisture in the material, usually when hygroscopic resins are dried improperly. Too hot material during injection molding is also one of reasons.

In this passage we talked about Warping, Weld line, Silver marks, and 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
Skype: sinomould-13
MSN: dkm@dakumar.com