04/08/2026
Why does a functional part still get rejected by the customer?
Because visual defects do not care that the part is functional. In plastic injection, a component can clip, seal, position, and assemble correctly, but still be rejected because ๐๐ต๐ฒ ๐๐๐ฟ๐ณ๐ฎ๐ฐ๐ฒ ๐ฑ๐ผ๐ฒ๐ ๐ป๐ผ๐ ๐น๐ผ๐ผ๐ธ ๐๐๐ฎ๐ฏ๐น๐ฒ. From flow marks and stripes to contamination or transparency variation, these can create a claim even when the technical function is not affected. For visible parts, the customer often reads the surface before they read the dimensions.
The difficult part is that aesthetic defects are rarely isolated cosmetic accidents. They usually come from ๐ฝ๐ฟ๐ผ๐ฐ๐ฒ๐๐ ๐ฝ๐ต๐๐๐ถ๐ฐ๐. Flow front instability, mould temperature imbalance, gate position, venting, drying conditions, masterbatch dispersion, fibre orientation, holding pressure, cooling rate, polishing condition, and handling after demoulding can all change the surface. A small black dot may be contamination. A gloss variation may be mould temperature or flow speed. A sink mark may be due to wall thickness, packing pressure, or rib design. A scratch may not come from the mould at all, but from manual handling, packing or secondary operations.
At , aesthetic control is linked with process control, metrology, and production handling. The point is not only to sort good-looking parts from bad-looking parts. The point is to understand ๐๐ต๐ฒ๐ฟ๐ฒ ๐๐ต๐ฒ ๐ฑ๐ฒ๐ณ๐ฒ๐ฐ๐ ๐ถ๐ ๐ฏ๐ผ๐ฟ๐ป. Is it material-related, mould-related, process-related or handling-related? This distinction matters because the wrong root cause creates the wrong corrective action.
For purchasing, this is where many commercial discussions become subjective. One side says the part is functional. The other side says the part is not acceptable. If the visual criteria are not aligned early, aesthetic quality becomes a grey-zone conflict. Star Plast Engineeringโs value is in treating ๐๐ถ๐๐๐ฎ๐น ๐พ๐๐ฎ๐น๐ถ๐๐ ๐ฎ๐ ๐ฎ ๐ฝ๐ฟ๐ผ๐ฑ๐๐ฐ๐๐ถ๐ผ๐ป ๐ฑ๐ถ๐๐ฐ๐ถ๐ฝ๐น๐ถ๐ป๐ฒ, not as an opinion. Because if the customer can see the defect, purchasing will eventually see the cost.