There was something wrong with my friend's copier once. I went to have a look and immediately told him that there was something wrong with the "phenomenon wheel" inside. Phenomenon on the surface of the roller, "the aging of polyester amine silicone rubber leads to the decrease of the brightness of the roller surface, and the roller surface is sunken and toner accumulates during printing, resulting in ghost printing."

My friend immediately took it and gave me a thumbs up, because our company is making consumables for printers and copiers, haha!