A SERVO-HYDRAULIC injection molding machine is a full-hydraulic IMM with a servo motor to drive the hydraulic pump. These high-end injection molding machines often have a fixed-displacement-pump, but could also have variable-displacement pumps with a swashplate.
These types of servo hydraulic injection molding machines employ hydraulic cylinders to clamp together two halves of a mold at high pressure. Plastic substrate pellets are then melted, and the liquid is injected into the mold cavity.
Servo-hydraulic injection molding machines systems are driven by hoses, valves, and pipes. One of the big reasons hydraulic machines continued to dominate injection molding is because the machine itself was cheaper than electronic machines.