Know about knit lines

About Knit Lines

The plastic injection molding process is a simple standard job, the plastic raw material is heated to its melting point ( for example ABS resin). It was forced into your injection molds to produce your plastic parts through the injection molding machine. The molten material is often the coolest surface and solidifying at all of the leading edges.

When the molten plastic meets an obstruction, then the flowing resin must travel around and meet at the other side.  It can easily happen knit lines on plastic parts surface when they meet past an obstruction.

If the plastic has too much cooling during the plastic injection molding process.

Cnmoulding technicians try to minimize, but we must balance this with other challenges like avoiding sink marks or blush, to achieve the perfect surface. So what we can do to help avoid knit lines happen when designing the new part at the beginning.

A few things should be considered

•  the Big thickness part design will slow down the cooling rate of the plastic resin, so help to improve the appearance of the knit line.
•  Difference plastic resin selection is one of a variable quantity.
• Fiberglass resin has less knit lines than normal materials, Fiber rough surface will cover this problem happen.
• In fact, additives like flame retardants, lubricants and mold releases can further exacerbate the problem.
•  Cnmoulding will optimally place the gate so that the knit lines are minimized, usually, it should move to a less critical area through improving our job.

In response to knit lines happen

If you are concerned about potential knit lines to happen in your new project?

Please use CAE software to analyze the mold flow of your part and address any design issues that can be easily modified.

You should review similar plastic resin that may a good way to show the knit line position there.

Remember, good industrial design and injection mold design, improve the right gate point, a knit line can often be reduced easy.