3D printing technology can indeed be used to manufacture weapons, including some weapons that are difficult to detect. Because 3D printing can create complex structures and can use non-metallic materials such as plastics, some types of weapons are more difficult to identify during security inspections. However, this use involves major legal and ethical issues. Many countries and regions have strict laws and regulations on the manufacture of weapons, and the use of 3D printing technology to manufacture weapons may itself violate these laws. In addition, weapons that are difficult to detect may pose a serious threat to public safety, so most countries will regulate the dissemination of related technologies and knowledge. It should be our common responsibility to advocate and promote the legal and safe use of weapons and maintain public safety.