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Why are the machines more repeatable?
- Hydraulic oil tends to behave differently as temperatures change and also as the oil becomes dirty. Temperature changes result in viscosity and flow variations through the hydraulic system. This is why many machine manufacturers incorporate an oil pre-heat cycle when initially starting the hydraulic pumps to reduce the time necessary to warm the oil to operating temperatures (wasted energy). Also, as the oil temperature migrates into the steel of the valves, pumps, cylinders, etc., it often results in behavior changes from the thermal expansion and tolerance change between components. As oil becomes old, it can begin to break down resulting from heat and moisture. The most common visual change comes from what is known as “varnish” build-up. This brownish build-up can be found on all areas where the oil experiences higher temperatures. Frequently, when removing the spool from the valve body, you can actually see varnish built up on the lands of the spool.
- Mechanical drives with servo motion control use absolute encoders with capability to detect as low as 0.01mm positioning. This capability, working in conjunction with tight machine tolerances, enables precise and repeatable machine operation.