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Author Topic: Replacing X and Y with rotation  (Read 886 times)

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Replacing X and Y with rotation
« on: June 29, 2016, 10:11:41 AM »
Hello to everybody,
 I am planning one project for quite some time and I am looking for software that could help me. I want to build simple cnc machine, that could cut off outer part of circular plate approximately 2mm thick in specific shape. I would like to use only two motors. One for rotating the plate and second for moving spindle in and out towards center of rotation.
 
The problem is software. I get data in 2D - X and Y coordinates  (drawing in CorelDraw). Point of my question is - is it possible to setup Mach to translate coordinates from X and Y G-code to angular coordinates or do I have to prepare special G-code for this ? Did anyone solve this issue ? Is there some software, that can already do that ?

I attached picture of desired function, hope it helps.

Thanks in advance.
Re: Replacing X and Y with rotation
« Reply #1 on: June 29, 2016, 12:22:43 PM »
Your project of two axis motion is not a machine motion of X and Y. It is a motion of one axis rotating, and the other axis a linear radius change with respect to rotation.
You can draw it in X and Y coordinates, but a machine as you desire does not equate to the same thing.
In your picture, Y would be a vertical motion, and the X is a horizontal component. Y is always a vertical linear motion; same for X being always a horizontal linear motion.
When the X and Y create a circle, they are moving in a related motion that is a function of the sine and cosine functions.

You need to construct a drawing, where each rotational unit has a corresponding horizontal displacement.
I assume you are intending to use an end mill to cut the material, as the table rotates (the A axis).
If you lay out the drawing on radial graph paper, with a center point, and lines (degrees) radiating outward, and the other axis concentric rings (the X axis), you can plot your proper coordinates. As you turn the drawing about the center point, and measure the X displacement (radial rings on the paper), this is your machine motion.

There may be some CAD program that can do this, but I am not aware of any.  The motion is like a machine cam, that imparts motion to a follower as it rotates.
The method you arrived at your shape may have the ingredients necessary to create your two axis motion in a simple manner.

Also, if you can plot the action in Excel, with the vertical displacement equal to the horizontal motion of the cutter, and the long axis (horizontal left to right) your degrees of rotation, this will yield your coordinates for machine control.

Re: Replacing X and Y with rotation
« Reply #2 on: June 30, 2016, 10:54:46 AM »
Why try to make the part with a X/A rotary motion, when a standard XYZ motion can easily cut the shape? A CAD program can create a .dxf file from the drawing, and a program like CamBam can produce the Gcode from a .dxf file.