Fusion not using G2 on simple circular 2 d contour

[jscott6SWZG]

I am making cylinders which nest....every time when I start lapping the fit I can feel ridges.

So I check the g-code and yup the main circles are linearized...

How do I talk fusion into giving me a nice circular toolpath?

See spring comp top setup and t2 2d Contour9

[engineguy]

@jscott6SWZG 

Have you tried enabling the "Allow Helical Moves" ??

You should just get X, Z and I moves, no Y so should be smoother I think ? 🙂

[jscott6SWZG]

Yes the nc program ran with helical moves ticked off

Yes the y value is constant at 7.45 throughout the code.

Yet you can clearly see the straight lines in the simulation and the actual part.

[engineguy]

@jscott6SWZG 

I meant "have you tried it with the Helical turned on ?? If it is on there are no Y values so the machine is not moving XtoY etc ??

[jscott6SWZG]

Yes I ran it with helical moves turned on (that is the helical moves box is ticked)

Yes i ran the part with helical moves turned on.

The gcode has a Y  constant value of 7.45  the x value alternates between 1.425 and 15.775 

[jscott6SWZG]

I am just starting to read g code....do I have xy moves?

[serge.quiblier]

Hi @jscott6SWZG 

It can be a post issue.

Are you using a post from the Autodesk library?

Have you tweaked it?

Can you share it?

Because i tried to post using the Rs274D post, and the partial rezsult is :

%
(spring copressor)
(Machine)
(  vendor: Sainsmart)
(  model: 4030 Generic 3-axis Router)
(  description: Prover xl This machine has XYZ axis on the Head)
(T2 D=6.35 CR=0 - ZMIN=-18 - flat end mill)
N10 G90 G94
N15 G17
N20 G21
N25 G28 G91 Z0
N30 G90

(2D Contour9)
N35 T2 M6
N40 S27000 M3
N45 G54
N50 G0 X17.68 Y8.085
N55 G43 Z15.225 H2
N60 Z5.225
N65 G1 Z1.36 F508
N70 G18 G3 X17.045 Z0.725 I-0.635 F990.6
N75 G1 X16.41
N80 G17 G3 X15.775 Y7.45 J-0.635
N85 G2 X1.425 Z0.475 I-7.175 F508
N90 X15.775 Z0.225 I7.175
N95 X1.425 Z-0.025 I-7.175
N100 X15.775 Z-0.275 I7.175
N105 X1.425 I-7.175 F600
N110 X15.775 I7.175
N115 X1.425 Z-0.525 I-7.175 F508
N120 X15.775 Z-0.775 I7.175
N125 X1.425 I-7.175 F600
N130 X15.775 I7.175
N135 X1.425 Z-1.025 I-7.175 F508
N140 X15.775 Z-1.275 I7.175
N145 X1.425 I-7.175 F600

Some I,J values means that arcs are outputted. In fact, helix and arcs are mixed, as some have Z values, and others don't.

Regards

PS : I posted in millimeters, but it should not matter for the use of arc/lines.

[jscott6SWZG]

Post is grbl/grbl_jscott6WZG

seth madore helped me modify the end of program to return the tool to the origin 

otherwise straight from library 

not sure what you mean.  Does the code show linearization ?

[engineguy · Accepted solution]

@jscott6SWZG 

Below is a snippet of code from your Contour 9 with the "Alloiw Helical Moves" turned on using the grbl Post Processor, you will see that there are no Y moves, there are G2 and G3 commands, the G2 command use the "I" which is an "Incremental Arc" around the axis, in the code you will see that the "I" position is a constant 7.175 and goes from -7.175 to +7.175 which is a 180degree arc so as far as I can see the grbl PP with the "Allow Helical Moves" option turned on is producing both G2 and G3 commands.

Should work 🙂 🙂 🙂

(2D Contour9)
M9
T2 M6
S27000 M3
G54
G0 X17.68 Y8.085
Z15.225
Z5.225
G1 Z1.36 F508
G18 G3 X17.045 Z0.725 I-0.635 F990.6
G1 X16.41
G17 G3 X15.775 Y7.45 J-0.635
G2 X1.425 Z0.475 I-7.175 F508  G2 command on this line, will not change until there is G0, G1, G3 command, it is "Modal"
X15.775 Z0.225 I7.175
X1.425 Z-0.025 I-7.175
X15.775 Z-0.275 I7.175
X1.425 I-7.175
X15.775 I7.175  See these moves going + and - through 180 degrees
X1.425 Z-0.525 I-7.175
X15.775 Z-0.775 I7.175
X1.425 I-7.175
X15.775 I7.175
X1.425 Z-1.025 I-7.175
X15.775 Z-1.275 I7.175
X1.425 I-7.175
X15.775 I7.175
X1.425 Z-1.525 I-7.175

Hope the above is of some help 🙂 🙂 🙂

[jscott6SWZG]

got it.  G stands for global

[jscott6SWZG]

I changed the tolerance to .001 and smoothing to 0.001 seems to have fixed up the simulations up

[ktorokU233T · Accepted solution]

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@jscott6SWZG wrote:

I changed the tolerance to .001 and smoothing to 0.001 seems to have fixed up the simulations up

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Simulation does attempt to give you a good perspective of how your tool path will look cut on the part. One of the limiting factors in how well it represents that tool path comes down to the graphics on the computer. One setting you may try and adjust is in the simulation pane that opens when you run a simulation.

It does help to turn the accuracy up thus showing a more realistic looking simulation with less pixelation and display artifacts. Keep in mind it also slows down simulations, sometimes drastically depending on the horsepower of your computer.

[jscott6SWZG]

Yeah that might be it i have other inaccuracies that i have been ignoring 

pretty sure i have enough computing horsepower