Shot cylinder controller

摘要

A die casting machine has a hydraulic shot ram controlled by a servo system that includes pre-settable thumbwheel switches to establish a desired memory of shot speed values and shot position presets in a programmable computer. An analog output responsive to the control program in the programmable computer produces a direct current analog velocity command signal. A servo amplifier includes means for comparing the command analog signal and a feedback signal from transducers sensing velocity of the hydraulic ram and position of valve means to produce an on-off servo valve signal so that a servo valve will modulate flow from a third state Olmsted shot valve so as to compensate for shot speed changes produced by changes in operational conditions including wear and build-up on a cylinder and ram; hydraulic oil heat-up during operation of the machine; and changes in flow characteristics of a molten metal due to temperature variations thereof.