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Members Machines / Re: BF20 Mill conversion
« on: Yesterday at 19:50:28 »
My opinion is that an air spring on the vertical axis is always a plus. Sure, it adds complexities (like always requiring an air supply and having LARGE exhaust capabilities on both ends of the cylinder for rapids), but having a zero weight spindle is important to me, so that all the motor has to move is inertial mass.
Some (few) machine controllers know how to program drive currents to the motors to counteract weight, using higher current to lift. Most don't, and some power supplies cannot cope, even if the controller knows how.
To that 'exhaust' issue, I provide the largest lines I can to and from a balance cylinder, and a large-capacity reservoir on the bottom end, so there's a place for the lift air to go rapidly on the down-stroke, and a place for it to come from rapidly on the way up.
That, because most low-pressure regulators don't have a high-volume relief path for excess pressure nor the ability to relieve tiny increases in pressure quickly -- they usually show some hysteresis.
Since the reservoirs work at relatively-low pressures, I just make them up from PVC pipe, caps, and an air fitting. If the reservoir has a volume of +10X the cylinder, the cylinder never sees any appreciable pressure change during rapids.
Lloyd
Some (few) machine controllers know how to program drive currents to the motors to counteract weight, using higher current to lift. Most don't, and some power supplies cannot cope, even if the controller knows how.
To that 'exhaust' issue, I provide the largest lines I can to and from a balance cylinder, and a large-capacity reservoir on the bottom end, so there's a place for the lift air to go rapidly on the down-stroke, and a place for it to come from rapidly on the way up.
That, because most low-pressure regulators don't have a high-volume relief path for excess pressure nor the ability to relieve tiny increases in pressure quickly -- they usually show some hysteresis.
Since the reservoirs work at relatively-low pressures, I just make them up from PVC pipe, caps, and an air fitting. If the reservoir has a volume of +10X the cylinder, the cylinder never sees any appreciable pressure change during rapids.
Lloyd
