Following are some of the common defects in Injection Molding. The solutions mentioned are possible solutions and must be tried out with safety in mind. Please always follow the material manufacturer and machine manufacturer's guidelines for safety.Paragraph.
Molten Plastic is not reaching the mold cavity section
Molten Plastic is flowing into unwanted sections of the mold cavity
Plastic is shrinking as it cools but additional plastic cannot be for further compensation of the shrinkage
A layer/ streak of a unwanted gaseous byproduct from the melt or moisture in the material comes in between the melt flow and the cavity walls preventing the texture from being picked up and in addition eventually leaving a residue
A differential cooling rate of the melt in two sections of the molded product
When air and gasses get trapped inside the mold cavity during plastic injection, the high pressure results in the dieseling of the plastic resulting in the burning of the plastic.
This can be degraded plastic and/or foreign material that can get mixed with the plastic that needs to be molded.
Usually occur with the parts are thick. The walls solidify and the plastic melt shrinks towards the wall and therefore sucks a vacuum void on the inside of the part
When moisture and/or a gaseous byproduct gets mixed with the melt and is injected in the mold cavity this moisture or gas if embedded inside the melt can show up as bubbles
Shows up at the gate when the material is sheared differently compared to the rest of the part
Usually seen with the part is thick causing the injected plastic to ‘snake fall’ on to the cold mold surface and start freezing immediately. When the fresh plastic come in it does not blend well with the first material causing the jetting marks
The melt flow front is usually cold due to the exposure to the cold cavity. When two flow fronts meet as in a flow around a mold pin they do not fuse uniformly causing a weld line. Sometimes air can also get trapped in to form the defect
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