Arc Precision Problem - I & J not to sufficient decimal places

[chris]

Hi

I'm having problems generating arcs.

I'm getting "Circle not congruent error"  from my controller on line 23 with the following code.

N20 G00 X72.145 Y190.486 Z15.
N21 G00 Z7.5
N22 G01 Z3. F800.
N23 G03 X72.111 Y190.498  I70.4 J185.8 F267.

So far as I can see the arc center (I&J) or the X,Y coords are not accurate enough for my controller. 

I've drawn a circle up in cad with a point on the circumference of (line 20) X72.145 Y190.486 (the theoretical start point)  and a center point of I70.4  J185.8 .  According to my drawing the resulting arc misses the target point (line 23)  X72.111 Y190.498 by 0.00049mm  which seems to be out of tolerance for my overly fussy controller???

I've hunted in the post and in the fusion 360 for any settings but can't seem to get I & J to any more decimal places otherwise I've tried to increase the X&Y decimal places to see if the problem lies there but to no avail.  Can anyone help.

Thanks in anticipation

PS - You'll note in the gcode, there is a Z movement on line 23 to perform a helical cut.  I'm sure my machine can perform helical cut it's a 5 axis fully interpolated machine.  for testing purposes I've taken the Z2.397 out of the code just to isolate the arc problem first. Right now I get the error with or without the Z movment

[johnswetz1982]

The very first section of the post is what I think you want to change,

capabilities = CAPABILITY_MILLING;

tolerance = spatial(0.0002, MM);

minimumChordLength = spatial(0.25, MM);

minimumCircularRadius = spatial(0.01, MM);

maximumCircularRadius = spatial(1000, MM);

minimumCircularSweep = toRad(0.01);

maximumCircularSweep = toRad(180);

allowHelicalMoves = true;

allowedCircularPlanes = undefined; // allow any circular motion

Not entirely sure though, I have not done much Post processor work.

[HughesTooling · Accepted solution]

The post is setup to output 3 places for MM and 4 for inches. The setting shown in the post above is just the smallest allowed arc.

This shows xyzFormat is used for formatting IJ.

Mark

[chris]

Thanks johnswetz1982  ... that didn't actually work, but I found it eventually.

For anybody else wanting to post to more decimal places. I changed the following in my post. 

var xyzFormat = createFormat({decimals:(unit == MM ? 3 : 4), forceDecimal:true});

On this line I changed the 3 to a 5 and all my outputs X,Y,Z,C,A,I&J posted to 5 decimal places
(use at your own risk, and do your own testing)

Thanks

[chris]

Thanks Hughes Tooling.   I'd just got there myself through plenty of trial and error.  I appreciate your answer which confirms to me I'm on the right path.

Thanks

[seth.madore]

There is also additional syntax added to both the Proto-Trak and Mitsubishi post to increase the accuracy of the arc calculation. On my Kitamura, I would have thread mill passes that would just do a straight Z move and ignore the arc command because it was off .0001". The added language cured that.

[Anonymous]

@seth.madore , when was this addition made to Mitsubishi post? 

[seth.madore]

When I ran into the problem 😛

However, the Mits logic does request that arcs NOT be 360 degrees. The syntax inserted into my post does allow for 360 degree arcs

-EDIT-

Turns out the Mitsubishi does NOT have the logic, my apologies. Looks like they just updated my post and didn't flow that into the OEM post

[Anonymous]

Aha. 

Haven't had the problems you described, but as you may remember I had other issues the other week. No more using R for arcs for me. 🙂

David