G540 dedicated machine application - have questions!

[blades]

These questions are similar, but more specific than my last G540 question thread.

I will be building a custom machine, and need to control 3 motors: 2 will control table motion and 1 will be used as a spindle motor.

This is a dedicated machine, so will run the same program. Once this simple program is developed, I would like to have control over the motor speeds (feed rate and spindle rpm).

In a nutshell and in rough terms, here's what the program will look like:

Beginning of program:
Spindle starts CW
Table moves 30", then rotates
Spindle reverses direction
Table moves back 30"
Spindle stops
End of program

Can the spindle motor be programmed solely with direction and rpm, regardless of number of steps (or inches of travel)? Remember, this is NOT a spindle motor per se, it's basically a 3rd axis stepper motor. I just need to know if (and how) it can be programmed.

ALSO: Is a PC the only manner of controlling the G540, or is there another means of storing and running a program on it? I know a PC is the normal method (and obviously the preferred method on a CNC machine), but this is a special application, and introducing a PC to the machine would unnecessarily complicate the operation. I would like to have a simple START/E-STOP button on it for the operator. I should mention that I'm not opposed to initially setting up and tweaking the program (feeds & speeds) on a PC. I just don't want the PC to be the primary operator interface.

Thank you for any help!

EDIT: I just read Mariss's thread on the G540/SD card setup. This would be PERFECT for the non-PC control I'm looking for. Assuming this eventually comes to fruition, this answers one of my concerns.

[rowbare]

The reprap project has developed a minimal g-code interpreter available for the Arduino micro controller.

http://reprap.org/bin/view/Main/Ardu...de_Interpreter

http://reprap.org/bin/view/Main/DocumentationMain see the Software / Firmware section for more links.

Here is a link to the Arduino project.
http://www.arduino.cc/

In your case though I suspect the G-Code interpreter would be overkill. You just need a fairly simple program to control your 3 axes.

bob

[blades]

Thank you for the links Bob, I will look into this. Looks interesting!

My issue with this project is that only 2 motors are programmed as an axis, while the 3rd motor needs to be programmed as a spindle motor, not subject to "inches per minute" or total steps. All the spindle needs to know is to run one direction at the start of the program, then reverse directions after the table travels "x" distance and rotates.

Mach and a G540 may be the most economical solution (actually, more of a work-around), but the more I look at this, the less I think the G540 will be of any value for this application. I believe it's capable, but I don't know if there's a program that would lend itself to this, since the number of steps for the spindle is unimportant and unknown. It could be calculated (and thus programmed as a Z axis), but it would be a moving target every time the table IPM or spindle RPM needed to be tweaked. Hell, I don't even know if something like this is programmable by G-code.

[rowbare]

Are you sure that what you need to do requires something this complex? It seems to me that what you are trying to do could be handled with a few reversible motors, a few switches and some fairly simple hard-coded logic.

Basic idea, hit cycle start switch, spindle spins up, traverse motor starts and table moves till it hits the limit switch. This shuts off the traverse motor and spindle and starts the table rotation. The table rotates till it hits the limit switch. This starts the spindle motor in the reverse direction, starts the traverse motor in reverse and the table moves till it hits the other limit switch. This shuts off the motors and triggers the reset logic... Maybe I am oversimplifying...

bob

[blades]

Oversimplified a bit... both steppers run independent chains that pull a table via a large sprocket (one chain pulls on each side of a large sprocket). This controls both linear and rotary motion of the table. So at the start of the program, both motors are pulling the table in linear motion. When the table reaches the necessary linear travel, one motor reverses direction, thereby transforming the linear motion to rotary motion. When the table has rotated 90 degrees, the other motor reverses direction, once again starting the linear motion. At this point, it's necessary for the spindle motor to reverse direction. The spindle motor will run a gang of disk cutters, much like pizza cutters, running one direction for the first set of cuts, and the other direction for the second set (this is a candy cutting machine, cutting a slab of candy).

Suffice it to say that there won't be technical-savvy people running this machine, which is why I really don't want a PC interface, just a simple start/stop button.

I do like your idea of reversable motors and limit switches, but I'd have to redesign the entire machine, and I like the flexability of programming I can have by using steppers.