On 11/09/2015 02:34 AM, Andrew wrote: > 2015-11-09 8:49 GMT+02:00 Eric Keller <eekel...@psu.edu>: > >> there were hydraulic milling machines sold based on Moog hydraulics >> and Bridgeport iron. I assume those two companies could screw things >> up, but the world has moved on. To move a long distance takes a lot >> of power. Small movements with a lot of force behind them are really >> easy, that's why you see fatigue machines and other shorter stroke >> machines with hydraulic servo. >> >> AFAIK the problem of hydraulic actuators is low efficiency. There should > be a high pressure high rate pump to provide high velocity and force. But > when the actuator doesn't move it all goes via baypass just heating the > fluid. Probably adjustable pump could help but it gets more complicated > (just a guess). > Yes, some systems had fixed displacement pumps and regulating valves, others had variable-displacement pumps. Then, you have to provide cooling for the variable displacement pumps so it doesn't overheat when the machine is idling. In either case, the drive motor has to be quite huge, so there is plenty of energy wasted, and they make a HUGE amount of noise. So much that sound barriers have to be placed around the hydraulic power pack.
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