[ryanpierce]

I'm trying to modify the Heidenhain ISO G-code post-processor in Aspire 8.0 to work with an old TNC151. So far I've had a lot of luck, except I'm having problems with arcs. None of them seem to work.

Here's an example that Aspire generated which blew up:

N114 X+1.8966 Y+1.7487
N115 X+1.9215 Y+1.7386
N116 G02 X+1.9375 Y+1.7309 I-0.0187 J-0.0596

It gave me an error: CIRCLE END POS. INCORRECT

Doing some math:

The arc radius from the endpoint of N115 (the start of the following arc) and the center I,J is 2.64535428251
The radius from the endpoint of N116 (the end of the arc) and I,J is 2.65190661412

So the radius error is 0.00655" between the two. This doesn't make sense to me. Given that Aspire outputs positions readable to 0.0001" for both G01 and G02, I'm very surprised to see that the arc endpoints would have such a different radius relative to the circle's center. Is the TNC 151 being unreasonable in its expectations of accuracy? Or is Aspire just being very sloppy?

I know I can set up a no-arcs post-processor, but I'd really rather get the arcs working. Any thoughts?

Thanks,
Ryan

[louieatienza]

I think Vectric sets their toolpath tolerance to .004" by default, you may want to try change that....

[Superman]

Check the CNC programming manual
- our Heidenhain, for the arcs, the IJK is the absolute center of radius

ie 2" semi-circle at X0Y0

G1 X+1 Y+0
G2 X-1 Y+0. I+0. J+0.