【169】Flow Marks on High-Gloss Housing – Fengchuang Breaks Through with Process Innovation

【169】Flow Marks on High-Gloss Housing – Fengchuang Breaks Through with Process Innovation

Keywords: Fengchuang Plastics, high-gloss injection molding, process technology, sample making

Mr. Lin held a housing up to the light and stared at it again and again. A faint wavy line ran across the surface – like a finger trailing across still water. That was a flow mark. He had been fighting this problem for two months.

Mr. Lin is an injection molding engineer at a speaker company in Foshan. The company was developing a high-end Bluetooth speaker, and the housing required a high-gloss piano-finish surface with absolutely no defects. But the molding shop they had been working with had run dozens of shots, and every single one had flow marks. They adjusted the process, changed the material, modified the gate – nothing worked. The project was already a month behind schedule, and the launch date kept getting pushed back.

Mr. Lin’s supervisor called him in for a talk. “If this project gets delayed any further, the customer may cancel the order.” Mr. Lin started losing sleep, staying up late searching for solutions. He tried over ten different approaches. The flow marks went from “obvious” to “less obvious,” but under sunlight, they were still clearly visible.

Then he came across a case study online – Fengchuang had done a similar high-gloss product for a certain brand. The next day, Mr. Lin went to Fengchuang’s facility. After examining the location of the flow marks, a Fengchuang engineer said, “This is exactly where the melt fronts meet. A conventional gate design won’t solve it. You need a different injection method.”

Fengchuang’s solution was three-pronged: change from a single gate to a multi-point sequential valve system, so the melt fills from four directions simultaneously without merging in the middle; raise the mold temperature from 60°C to 90°C, improving surface gloss by one grade; and switch to a high-flow material grade for faster filling. The flow marks disappeared.

When the first sample batch arrived in Mr. Lin’s hands, the surface was as smooth as a mirror. He turned it under sunlight – not a single streak. Mr. Lin took a photo and posted it in his work group chat with just two words: “We nailed it.”

After launch, that speaker’s high-gloss housing became one of its key selling points, and sales exceeded expectations. Mr. Lin now oversees injection molding for all of his company’s high-gloss products – and all of them are done at Fengchuang.

Can’t achieve a mirror finish on your high-gloss product? Come to Fengchuang. We break through flow mark challenges with process innovation.