hi- I am brand new to cnc and Mach 3. I am having trouble with the formulas. Moderator, if this should be a new thread let me know. The machine is custom built. It has two axis. No Z. It is going to be a portable cnc plasma. For now it is proof of concept phase. A axis is rotate(rotary table), and B axis is linear on the on top of the rotary table. It looks like a "banjo". The tool is held on the B axis and is constrained to a line that passes through the center of the rotary table.

Right now it is just drawing with a marker on paper.

I want it to run on standard x y gcode. My formulas are as follows.

A= arctan(y/x)*57.2957795

B=((x^2)+(y^2))^.5

It tests fantastic on the test feature on the formulas window.

All four axis (X Y A B) home at the rotary table's center.

I have been using very simple X Y gcode.

A note on something I read in the thread. I found the formulas work in MPG, Gcode, and STEP. Not on Hot keys and buttons.

Here is the problem. My test is a 5"square. I have drawn it at many locations on the table. It is consistent does not lose steps. It draws a complete square and it closes it. The size of the square is good and the corners form a perfect square. The lines that connect the corners are arcs.

If you draw a circle, the machine will drop the A and B axis completely.

I think my formula,s scaling and backlash(lack of) are good, The program seems to get it goofy or drop it completely. I have the problem at all feed rates. It it processing power on my computer?

Any thoughts would be helpful.

Adrian