There are two types of systems used to generate tonnage, Hydraulic Cylinders and Toggle Linkage Systems. Many toggle systems used hydraulic cylinders to actuate them, but the actual tonnage is applied through the mechanical advantage of the linkage system.
How is clamp tonnage adjusted?
On a toggle clamp, the tonnage is generated by the mechanical linkages and the
stretch of the tie bar. The movement of the rear platen (die height) adjusts
the clamp tonnage on this machine.
On a cylinder clamp, there is no toggle, just one or more hydraulic cylinders
holding the mold closed. The adjustment of the hydraulic pressure adjusts clamp
tonnage on this machine.
On a cylinder clamp, the tonnage is determined by a direct relationship between the hydraulic pressure and the clamp tonnage. ie. Max pressure = Max tonnage.
On a toggle clamp, the tonnage is determined by an indirect measurement of the tie bar stretch using a strain gauge on one or more tie bars. ie. Max strain = Max tonnage.