Table of Contents
What causes bubbles in injection molding?
Gas bubbles may stem from flow-front issues, such as converging fronts, jetting, or mold/machine problems such as non-vented core pins, poor venting (try vacuum venting), too much decompression, or resin degradation due to overheating or long residence times.
What causes voids in plastic parts?
Causes: Vacuum voids are often caused by uneven solidification between the surface and the inner sections of the prototype. This can be aggravated when the holding pressure is insufficient to condense the molten plastic in the mold (and thereby force out air that would otherwise get trapped).
How do you get bubbles out of plastic?
By using a hot air gun or small lighter, warm the area of the part that has the bubble until it begins to soften up. If the bubble expands, you’ve got a gas pocket. If the bubble collapses, it’s a vacuum void. Gas pockets are usually a result of jetting which is a front flow issue.
What causes cold slug in injection molding?
Cold slugs – A small non-uniform area on the part caused by an improperly heated piece of plastic becoming attached to the part. Flow marks – A wavy pattern or discoloration caused by a slow injection speed which allows the material to cool too quickly.
What causes porosity in injection molding?
Once the material is injected into the mold cavity, it begins to cool and shrink. This shrinkage can cause voids or porosity to form in the middle of the wall thickness, as the material shrinks towards the mold wall that is causing the cooling. Porosity is generally found in thicker sections of parts.
What causes holes in plastic injection molding?
The important thing for the manufacturer and client to do is to detect the defects and then troubleshoot the problems that are causing them. This blog focuses on the two major source of holes – voids and bubbles – in plastic injection molding: vacuum voids and gas pockets.
What are bubbles in injection molding and how to get rid of them?
Let’s go through the possible causes—and fixes—to get rid of bubbles. What are Bubbles in Injection Molding? Bubbles, sometimes known as gas traps or blisters, are cosmetic defects that detract from the looks of the part, which is especially irritating if the part will be seen.
What causes a bubble in the plastic?
Bubbles can be caused by using a material that is not sufficiently dry. Most plastics will absorb moisture from the air. Before it can be used in injection molding it must be thoroughly dried.
Why are there bubbles in my mold?
Large bubbles or voids are usually caused by thick sections that are starved for material as the material shrinks during cooling. This can cause surface sinks and/or internal voids (bubbles?). There are other mold flow problems that can also cause bubbles.