Hydraulically controlled CNC axis

[Jim Cliff]

Hi,

I'm looking to build a 3 axis cnc machine about the size of a van.
All 3 axis will be controlled by hydraulics and actuators will consist of 2 hydraulic motors (x axis), 2 rams (Y axis) and 1 hydraulic motor (y axis).

I was thinking of using rotary encoders connected to each axis and fed back to a motion controller. The motion controller will convert G-code to +/-10vdc pwm signals to control proportional hydraulic valves.

Can anyone point me in the right direction for suitable hardware / advice?

Many thanks,
Jim

 

[HPost]

What travel rates are you hoping to get?

What position control do you need +/- 0.00?

How quick do you need it to be? In other words, how quickly do you want to go from 0 to say 1000mm on each axis?

What force and torque are you anticipating needing on this?

 

[Jim Cliff]

Maximum travel rate would be 0.3-0.5 meters / second.
Position control accuracy to 0.25mm

Torque and force not calculated yet.

Hydraulic circuitry & design not a problem, I can calculate and build this when required.

I'm more focused on the electrical side of things at this stage of the design. I have experience with electrical CNC machines (lathes / mills etc), a lot of experience with hydraulic circuit design and implementation. Designing a hydraulic CNC will be a first for me, but considering I know both separate subjects well I'm hoping it should be easier to grasp.

My main questions are:

1. What CNC motion controllers (PWM or analog (+/-10vdc) are available that are compatible with hydraulic proportional valves?
2. Method of feedback? Rotary encoder to motion controller? Spool LVDT sensors to controller?

Thanks,

 

[HPost]

The questions I posed were not so much about the fluid side, more about knowing the power that you are looking to control.

The theory behind any system will be the same, but the power and control requirements will drive the cost up.

Linear transducer attached to a slide way

Rotary transducer connected to a ball screw

Position fed to a controller. A digital or analogue controller that will measure position and provide output current to the actuator. A PID controller most probably.

The level of precision and control needed will dictate the cost of the controller and the software needed to drive it.