Flash and Angel Hair — Injection-Moulding Fibres and Edge Flash
Flash — thin, unwanted plastic webs or threads at a part's parting line or edges — forms when molten polymer escapes into the gap between mould halves during injection moulding.
What it is
Flash, also called angel hair for its fine, thread-like strands, is thin excess plastic that forms at the parting line or edges of an injection-moulded part. It occurs when molten polymer is pressed into the small gap between the two mould halves during injection, rather than staying fully inside the cavity.
What causes it
Flash is mainly a mould and process issue — insufficient clamping force, worn mould surfaces, or too high an injection pressure. But feedstock consistency plays a role too: uneven melt flow or moisture content can make a material more prone to stringing at the gate or parting line, which is why processors watch MFR and dry their material to spec before moulding.
Why it matters for recyclate buyers
Recycled feedstock can vary more than virgin resin if it isn’t properly sourced and processed. Consistent regranulate with a stated MFR and material stream reduces the melt-flow variability that contributes to stringing, so a moulded part behaves closer to what a virgin-resin process would expect.
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