Mould structure traces on injection moulded parts are the mould structure traces printed on the molten plastic during the moulding process, referred to as mould structure traces, such as parting surface traces, gate traces, top bar out of the mould traces, core traces and insert traces, etc. Mould structure traces are the traces formed after the molten plastic has condensed into the mating gap of the mould parts. The mould structure traces of plastic injection moulding process are visible to both eyes and have a certain shape, part, size and characteristics. Traces of the injection moulding process, referred to as defect traces or deformation traces, such as flow traces, melt traces, shrinkage traces, silver lines, injection traces, discolouration, rise and shrinkage (deformation) and cracks and dozens of other kinds. Defect marks have an irregular shape, position and size, but have specific characteristics. The majority of defect marks are visible to both eyes in terms of shape, position and size, while only a few are invisible, such as stress marks, looseness and bubbles (visible in transparent injection moulded parts, but not in opaque ones). The characteristics of defect traces of plastic injection moulding processors are distinctly different from mould structure traces, as the characteristics of defect traces are very different from each other. As long as the characteristics of defective traces are mastered, it is not difficult to distinguish them.