The reason why the surface of the home appliance casing is smooth is because most of the home appliances are spray-coated. But from the photos, your product should be directly added with black masterbatch. The cost of spraying is very high, so I’m afraid it’s not suitable for you. products.
However, there are also direct injection molding of home appliance shells that do not require spraying, but the mold requirements are very high, and the mold surface must be very smooth. I don’t know if your part is injection molded or not. . ?
If it is injection molding, it would be more suitable to change the mold. Polish the mold, or re-plat it into a mirror surface. Polishing is very cheap, can be done within a few hundred yuan, and is very convenient. Of course, the effect is definitely not as good as a mirror mold.
Household appliance casings that are directly injection molded also use spray-free high-gloss materials, and the matching of color masterbatch is also very important. The surface finish of PE is definitely not as good as those of high-gloss ABS and PC.
As for the glue stain, I didn’t see it clearly. There is a white mark next to the round hole in the lower left corner, which looks like a flow pattern. If the flow channel comes in from that position, then change the two round holes to Go up there and stay away from the flow path and there won't be any.
PE is the same as PP, if it is sprayed or printed directly, the paint will peel off. It needs to be soaked in PP water. The price of PP water is not very high. It can be found anywhere that sells paint. Just ask.