Lightweight mechanical arm

The utility model relates to a light-weight mechanical arm which comprises a base, a mechanical arm big arm, a mechanical arm small arm and a tail end executing mechanism which are connected in sequence. The mechanical arm is characterized in that the middle of the mechanical arm big arm is hollowed out, an arm body of the mechanical arm big arm is divided into an inner layer and an outer layer, the inner layer is made of titanium alloy, and the outer layer is made of carbon fiber composite materials; when the thickness of the titanium alloy and the thickness of the carbon fiber composite material are both 5 mm, the mechanical property of the mechanical arm is the best, 25 layers of carbon fiber composite materials are arranged in total, the thickness of each layer is 0.2 mm, a symmetrical layering mode with the layering angle being 1 is adopted, and s represents middle plane symmetry and middle plane single symmetry. The mechanical properties such as strength and rigidity of the mechanical arm are improved b