As a plastic injection mold maker, your job is to operate and monitor mold machines. This involves setting the machine up, running it, testing molds to ensure they meet specifications, modifying molds as needed, and inspecting finished products. Plastic injection mold makers also use shop equipment and tools to finish molded polymers, perform maintenance on molding machines, select materials to use, and schedule jobs to meet quoted hours and delivery times. Mold makers often supervise assistants as needed, ensure the work area remains clean and free of obstructions, and report any problems to the supervisor. Some companies have plastic injection mold makers work in shifts with machines that are in use both day and night.