Re: Simple Vector Feed Rate Setting Question

--- In CAD_CAM_EDM_DRO@y..., "Dan Statman" <dan.statman@r...> wrote:

> There must be an error in the TurboCNC program then.

Intermittently,

> depending on the relative contributions of the angular and linear

axes, the

> movement speed will far exceed the speed if only the linear axis is

moved.

> This occurs without changing the feedrate.

Dan,
A while back I tried this with CNCPro, NOT TurboCNC, but thought the
similarities might give you an insight. This is a snip of code to
cut a gear tooth generated by GearGen set to .001 increments. I
intended to cut one tooth, jog the rotary, cut the next tooth, etc.
Then thought it would be cool to just leave the Y at zero and let the
X and rotary (A) cut the entire gear. Wrote a routine to calculate
the new X, A and feedrates. CNCPro uses only the X (and ignores the
A) if there is both an X and an A in the same line, so the new
feedrate for each step is based on the X component of the X-Y
vector. However if there is NO X in the line, then it uses the A,
which is in deg/min. Now on my Sherline, there is a 100:1 ratio
between steps/in and steps/deg, so you get some strange looking
feedrates, depending on the radius. Note lines N100 and N110 in the
converted code.

(original gcode)
N70 G00 X3.3312 Y0
N80 G00 A0.
N90 F8
N100 G02 X3.3305 Y-0.0711 I-3.3312 J0.
N110 G01 X3.3298 Y-0.0713
N120 G01 X3.3288 Y-0.0717
N130 G01 X3.3277 Y-0.0721
N140 G01 X3.3267 Y-0.0725
N150 G01 X3.3257 Y-0.0728
N160 G01 X3.3246 Y-0.0732
N170 G01 X3.3236 Y-0.0736
N180 G01 X3.3226 Y-0.0740
N190 G01 X3.3215 Y-0.0743
N200 G01 X3.3205 Y-0.0747

(After converting to X and A)
N70 G00 X3.3312 A0
N80 G00 A0.
N90 F8
N100 G01 A-1.2229 F137.6 (8 in/min at this radius)
N110 G01 X3.3305 A-1.2266 F7.6
N120 G01 X3.3295 A-1.2339 F7.4
N130 G01 X3.3284 A-1.2412 F7.5
N140 G01 X3.3274 A-1.2484 F7.4
N150 G01 X3.3264 A-1.2540 F7.6
N160 G01 X3.3254 A-1.2613 F7.5
N170 G01 X3.3244 A-1.2685 F7.4
N180 G01 X3.3234 A-1.2758 F7.4
N190 G01 X3.3223 A-1.2814 F7.7
N200 G01 X3.3213 A-1.2887 F7.6

BTW this did work, but it wasn't totally reliable. I don't
remember the exact problem, but thought at the time the federates
were somehow getting tangled up. Needless to say if the rotary is
used as a linear, then the feedrate is astronomical, and if vice-
versa, it comes to a dead stop. Never followed up on it, but if
anyone is using this method with success, I would be interested in
hearing from you.
Al Lenz