Many plastic injection molded components end up being, not just a cosmetic part of the product, but part of its branding. Designers want to apply the company name, model name, or company logo to a part as part of their marketing/branding effort.
If you are looking to add decorating to your plastic/composite part, talk to your molder about plastic selection. They will work with you to help with a material that is accepting of the ink, whether it is natural or through a pre-treating process.
Plastics through their make-up can be more or less receptive to decorating. Ink adheres to plastics differently because of their inherent surface tension. Polyethylene and polypropylene are two such plastics that are not receptive to decorating. In addition, if your design is intricate and ends up tempting the molder into using mold release spray, the resulting film will inhibit the ink’s ability to adhere.
When you know you are looking to decorate your plastic or composite parts, talk to your molder EARLY in the design phase, so the correct plastic can be selected OR accommodation for the design necessary plastic can be made. Certainly, a Design Requirement Specification that identifies what the decoration/ink will need to hold up to is a necessity. Is the item a single use? Will it be stored indoors or outdoors? Will it be washed? What solution and temperature will it see as it is washed? Will it be washed by hand or through an automated system? All of these use parameters will assist in getting a part that looks good out of the box and while it is in the customers’ hands. You branding being present for the length of time you choose, rather than the plastic.