Drive of a linear shaft with hydraulic motor

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31 Aug 2023 17:42 - 31 Aug 2023 17:44 #279498 by RobotMatic
I have a very large machine where the movements of the X, Y table and the Z spindle move with hydraulic motors.
Hydraulic motors are driven with a directional valve with 2 solenoids to give Cw - CCw
I have the idea of activating the movements by reading the position of the table with an encoder on each axis making an on-off on each solenoid.
I do not pretend to be presicion in the movement, only to perform the movement.
I was reading the pulse generator but I can not realize if it is possible some mode of 0-14 that can be useful for this.

The question is whether this type of drive is possible?
Last edit: 31 Aug 2023 17:44 by RobotMatic.

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31 Aug 2023 18:44 #279504 by andypugh
It's possible, and was even quite popular back in the early days.

One of the LinuxCNC folk has an old K&T CNC mill (from the 1950s, I think) that originally used hydraulic motors.

One interesting alternative that I have always wanted to try is to have a bank of solenoid valves with different orifice sizes, each twice the flow of the other. Then you can drive them with a binary number, 16 fifferent speeds with 4 valves, for example.

Traditionally, though, you would do this with a proportional valve (google for "moog valve")

I used to work with hydraulic testing machines which could be controlled to an accuracy of several microns at forces of 500kN or so.

You should be able to control position to setpoint with your proposed machine just ising the wcomp HAL component and the .under and .over outputs.
The following user(s) said Thank You: RobotMatic

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31 Aug 2023 23:35 #279522 by RobotMatic
Thanks for the answer, I'm going to study the wcomp component !!!.
This machine is from 1970, it is in perfect condition and I want it to remain original.
As always, thank you very much for the support!

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01 Sep 2023 00:09 #279524 by skunkworks
we were almost going to run a Cincinnati lathe that had hydraulic servos.. (but decided against it..) the plan though because the frequency response was so low of the whole system - was to use a carrier of around 1khz or more to 'buzz' the valves to keep them from sticking.. *using something like a servo drive like AMC to drive the proportioning valve..

I think this could all be done in hal...

sam

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01 Sep 2023 01:32 #279540 by RobotMatic
Here I leave a proposal that works very well for me on the desktop for the X axis

#
Wcomp

loadrt wcomp count=1
addf wcomp.0 servo-thread
setp wcomp.0.min -0.01
setp wcomp.0.max 0.01

net  0-in-wcomp    wcomp.0.in <= joint.0.vel-cmd
 
#

Tomorrow I will continue working on seeing how I can select the speed ranges since I have 2 multi-disc clutches, the first for fast movement and the second for machining movement and I also have a brake that must be activated when there is no movement

thank a lot!!!
 

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