Multi Axis Controllers

The difference is usually in the ability to perform interpolated motion, the use of simultaneous axis coordination to move smoothly through space, follow a countour or mimic human movements. This requires a lot more processing power and essentially defines a robotic controller, but is something rarely necessary in a CNC machining environment. That's not to say you can't do that with a CNC controller, but when you need to, it begins to look, and cost, a lot more like a robotic controller.

Thank you for your explanation. I have been curious about that myself.

I beg to differ. 4 and 5 axis NC/CNC controllers were developed to perform fully interpolated motion such as machining normal to a convoluted surface or swarfing (following a surface with the side of an end mill while staying in contact with an intersecting surface at the tip of the tool) before robotics.

I was programming NC/CNC machines back in the 1960's, long before robotics came out of the experimental labs, and was involved in developing offline graphical robot programming in the 1980's (when most robots were being programmed in teach mode causing lots of robot downtime).

That said, a fully articulated (6 axis) robot requires a slightly more sophisticated controller to integrate the extra (rotational) axis. The difference then is that CNC controllers handle up to 5 degrees of freedom and the robot controller handles all 6 degrees of freedom.

The robot controllers are an extension of what was originally developed for multi-axis NC/CNC.

Hooker

@Hooker: Would you then say that it will be possible to use a CNC controller for a say 4 or 5 axes robot?

Theoretically, yes. There are some fundamental differences, though. For example, by standards definitions, the axis directions between cnc and robotics systems are reversed which may make the rotations around those axes reversed; ie, right hand rule rotation vrs left hand rule rotation. Depends on the manufacturer. Some CNC controllers allow you to change these definitions in their base parameters so you have to have in-depth knowledge of your equipment.

So, it would all come down to the particular equipment you're trying to integrate.

That said, there are tons of open source programs and equipment available out on the net to address this stuff. For example, I'm currently in the process of building a Reprap Mendel, a 3 axis 3D printer. It's controlled by an Arduino board and open source programming. I'd like to expand that into a 4 axis rotational head system eventually.

If you google search for homemade CNC you'll find a lot of stuff out there.

Hooker