Factory Floor · All
Polishing and Deburring: Cleaning the Edge Before Plating
From the factory floor in Shenzhen: how cast pin blanks are trimmed, deburred, tumbled and polished so the plating goes onto a clean edge.
A blank comes off the die-casting machine with a sprue, a thin flash around the outline, and a faint seam where the two mold halves met. All of that has to go before plating, because plating copies every mark. This station removes the sprue, cleans the edge, and brings the surface up to the finish the plating needs.
First the sprue is cut. It is the small tag of metal where the alloy entered the mold. On most designs it sits on the edge and is clipped or snapped, then the spot is dressed flat. Where the sprue lands is decided at the mold stage; we put it where it is easiest to hide.
Then the flash. It is a paper-thin skin of alloy that squeezed out between the mold halves. On a good mold it is barely there. It is removed by hand with a blade or on a wheel, following the outline. Cutouts and inside corners take the most time, because the tool has to reach in without rounding the corner.
Next, tumbling. Blanks go into a vibratory tumbler with ceramic media and compound. The media rubs every surface at once. This takes the casting skin off, softens the edge slightly, and gives an even matte base. Time in the tumbler is set by the design: a pin with fine raised lines gets less, a plain shape gets more. Too long and the lines round off.
Then polishing, where the design calls for it. Bright gold and silver plating shows every scratch, so blanks going to a bright finish are polished on a cloth wheel before plating. Antique finishes are more forgiving; the darkening hides fine marks, so they usually skip the wheel. Hard enamel blanks go through this station twice: once now, and again after the enamel is ground flat.
Finally, a check. Each blank is looked over for a missed burr, a rounded corner, a pit that tumbling opened up, or a bent post. Rejects go back to casting. What passes goes to the plating line in trays, sorted by order.
This is the least visible stage of the process and the one that most decides how the edge of the finished pin feels in the hand. How we check it is on the factory quality page. The full process is on the custom enamel pins page.
Book a live video walk-through of the polishing station: email pin@guangdongcs.com or WhatsApp +86 187 1868 4696 (Bella, Export Sales).
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