On a die-cast metal lip gloss applicator, a visible line can relate to the mold junction, excess metal or a subsequent edge-finishing operation. These descriptions concern different aspects of manufacture. Identifying the feature’s location and physical profile makes a surface review more useful than assigning a defect name from reflected brightness alone.
The parting line identifies a mold junction
The parting line is where sections of the die meet. NADCA’s design guidance describes how its position relates to the casting and subsequent trimming. The International Zinc Association also notes that a witness of this junction can remain visible after trimming.
A witness is the residual trace seen on the component. Its presence does not necessarily mean a projecting fin of metal remains. Conversely, calling a feature a process witness does not automatically make its height, location or appearance acceptable. Those characteristics still need to meet the finished-part specification.
Sambound packaging sample showroom. Context photograph.
Flash is metal beyond the intended boundary
Flash forms when metal enters an unintended gap at a die interface. It can occur along a parting line or another moving-tool interface. Die condition, closing and casting conditions can contribute; a photograph cannot identify which condition produced an individual feature.
A thin fin can be flash even if it contains very little metal. Flash should therefore not be defined simply as a larger version of a witness mark. Its removal and the condition left afterward are part of the agreed finishing requirement.
A burr describes an unintended edge projection
Cutting or trimming can leave a raised projection at an edge. Such a burr may have an irregular or sharp profile. Trimming a flash fin can leave a burr at the same location, so the terms do not always identify mutually exclusive regions on a finished part.
Sharpness alone does not establish how the projection formed: a flash edge can also be sharp. Record the physical observation first, then use the known casting and finishing sequence to investigate its origin.
Review the relevant surface and finishing stage
Map the observed feature to the application surface, stem-fitting area or another identified zone. Record whether it follows a die junction or a cut edge, and compare its profile using suitable magnification or an agreed measurement method. A reflection moving with the light is not a measurement of projection height.
Where appropriate, compare identified samples before and after the relevant finishing stage. Use consistent lighting and orientation, and retain the same location reference. A decorative finish can change visibility without resolving every dimensional or edge condition.
For a selected die-cast applicator project with SamBound New Material Technology Company Ltd., whose site is sambound.com, agree the finished-surface reference and acceptance criteria for each functional zone. This connects casting terminology with the component that will actually be reviewed, without treating a showroom image as an inspection result.
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