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1

G-Code, CAD, and CAM discussions / Re: G-Code G15/G16 Polar coordinate

« on: July 30, 2015, 12:11:56 AM »

I now understand, why G15/G16 doesn't fit at all to my situation. I tried out the proposal of BR549 to use "formula axis correction" instead. It would be perfect if
a) I could distinct between cases (if ... then .. else) that appear in the trigonometric math and
b) if Mach3 would not only apply the formula to the endpoints of G1-lines, but also to all intermediate points. Without this, all lines appear to be arc. Why? Consider the example of moving from cartesian points (1,0) to (0,1). The polar coordinates are (1,0°) and (1,90°). So, Mach3 thinks: "twice the same x-values - so I don't have to move the x-axis" - yielding an arc from 0° to 90°, which is not what I expected. I expected a COORDINATED move from point to point, whereby the formula is applied to each intermediate point. That would give a real straight line.

I read about the cylindrical coordinates in the XZC-coordinate system: X and Z linear axis, C the rotational axis parallel to the Z-axis. Would that solve the problem maybe?

2

G-Code, CAD, and CAM discussions / Re: G-Code G15/G16 Polar coordinate

« on: July 27, 2015, 11:12:22 AM »

Thanks for Your thoughts,

but I run very small pieces of G16/G15 polar coordinate programs, found in the internet, and I had the same problem with all of them...

3

G-Code, CAD, and CAM discussions / G-Code G15/G16 Polar coordinate

« on: July 27, 2015, 10:07:34 AM »

Hi,
this is my first post in the cnc world at all :-)

I am building a larger 3D-printer with a horizontal X axis and a rotational Y axis (plus Z-axis) - just like a normal tower crane. I calibrated the Y-axis so that G0 Y360 yields a full turn.

I than converted the cartesion coordinates of the G-code output of the CAM program to polar coordinates and read the file into Mach3.
The geomety of my input file shows perfectly up in the mach3 toolpath window!

G90
G0x0y0
G16
G1x1y45 (e.g.)
...
G15
M30
%

But unfortunately, G1x1y45 didn't go to the 45° position. Rather, a first G1x1y1 yielded a 30° move. But any efforts to scale this, where unsuccefull. The following problems occured, but I was unable to find a reasonable reasoning behind it:
- The scaling factor is not always 1 : 30, sometimes 12° sometimes even non linear (depending on the x-value)
- Mach switched sometimes (only) the x-moves in G91 modes (incremental)
- any attempt to calibrate "motor tuning" in the G16 mode didn't work (sometimes even non linear)

Any help would be very much appreciated.

Hans