Re: [CAD_CAM_EDM_DRO] Re:Gcode

Ballendo et all:

I'm sorry but I'm still a little confused about the recent discussions of
g02 and g03. Would someone kindly let me know if I'm understanding
correctly. So:

At 12:55 AM 9/3/00 +0000, Ballendo wrote (in slightly different order):

>Okay:
>G0 X0Y0Z0 (keep it understandable, we'll start from zero)
>G90 G20 (absolute coordinate system, inches)
>G18 (select plane XZ for arcs)
>G02 X10 Z10 I5 K5 F25 (CW arc from 0,0,0 to 10,0,10 f/rate 25IPM)
>M01 (stop if operator has the optional stop switch on)

So g90/g91 absolute/relative and fx for feed rate. Then g17/g18/g19 for
the plane to be used as XY/XZ/YZ. Also, the first point on the arc is the
current location of the cutter, above set to 0,0,0. OK.

Now, g02 is a clockwise arc. Are clockwise and counterclockwise (g03)
defined by the third axis, here +Y, in terms of a right handed coord.
system? (Counterclockwise positive) This would seem logical.

Then in specifying the above g02 move the final point x10/z10 and the
center point x5/k5 have no Y specified so the start, end and center are in
the same XZ plane. This should create a circular arc in that plane.

Are the inputs X/Z and I/K absolute or from the start point? Do either
depend on the g90/g91 specified? I can't tell with the start point at 0,0,0.

But then for:

>G0 xoyozo (caps doesn't matter)
>G90g20G18 (spaces don't either,but some ctrls wld not allow multi G's)
>g01F25 (set 25 InchesPerMinute, is modal so not needed next line)
>G03 x2y0z0 I1 K-.25 (this will take ballmill to x2, max 1/4inch deep)
>M30 ( stop and rewind to start, for next part)
>
>Comments in gcode are in ().The control ignores them. G03 is CCW arc.
>If the G03 above was changed to G02 we would not cut anything! Just
>make most of a circle above the material, starting and stopping at
>the material surface. (Like tracing a hula-hoop buried partially in
>sand.)

For this move the same parameters are set (absolute/feed) and a plane
specified XZ. However, the parameters in the g03 code have X/Y/Z and I/K
set. I ran a couple of variants of this in EMC (no hardware
connected). It seems to not allow a center point off the plane specified
by g17/g18/g19 and the start point. The above code is OK in not specifying
a J for center location. In fact EMC won't allow entering a J in the above.

However, EMC allows an end point off this plane. A move like:

g03 x2y1z0 i1 k-.25

is allowed. But this doesn't look like an arc but a helix. It looks like
an arc in the XZ plane with a linear move in the Y. If this is true, the
center location really locates an out-of-plane axis (here the plane being
XZ so the axis is in the Y). Is this right?

Finally:

>A helical cut is very useful when milling. Means you dont try to
>"drill" with an endmill designed for side cutting. MUCH less strain
>on your machine!

Is the above how to get a helical cut?

Can anyone indicate a good reference to learn this from? Or would it be as
useful to just try different codes in EMC? Is EMC reasonably standard and
complete?

Eh, chances are I'll not need these but then again a helical would be very
useful for plunge cutting, etc.

Thank you.

Hugh

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Hugh & Denise Currin
currin@...
Klamath Falls, Oregon USA
541/884-3023
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