Re: [CAD_CAM_EDM_DRO] hydralic bed control

In a message dated 07/29/2000 4:09:21 AM Hawaiian Standard Time,
dengvall@... writes:

<< Hi,
I have an old horizontal mill with a hydralic bed. Has anyone tried
control of anything hydralic using a automotive power steering unit?

Dave >>
Dave,

Seems hydraulics fall into about 4 categories. First is low pressure stuff
from about 0 to 1200 PSI. Then you have the 1200 - 3000, the 3000 to 5000 and
then the 10,000 PSI stuff. You need to figure out what you have to prevent
failure. If your pump can produce more pressure than your actuator can
handle, you will have failure. All work quite well but have components that
get smaller and more expensive as the pressure goes up. Most likely, an older
bed mill or planer mill uses 1200 psi cylinders. Get an old power pack off of
a hydraulic elevator or other hydraulicly driven shop machine. (Most of these
will run stuff up to 2500 PSI) Convert the manual control valve to a three
position spring centered two coil hydraulic valve. Place a flow control valve
in the pressure supply line to bleed off excess flow to slow it down. Make
sure there is a safety valve set to your max working pressure in the circuit.
If you control the two coils with a PC or PLC along with limit switches, you
will have a neat table reciprocating drive. I have seen a few that had spring
loaded valves that were toggled by trip dogs mounted on the side of the
table. I doubt that would pass an OSHA inspection nowadays.

Peter
THRD, Inc.