Arc motion much smoother than line segments

[Derek]

When I do 3D work my cam program writes everything as line segments. Even a perfect arc. I have noticed that even with lookahead set at 300 or more there is a noticeable speedup and slowdown as UCCNC processes each line segment. If I convert the same line segments to arcs in the cam program it is one fluid motion. I use a .001" tolerance in the CAM program so the line segments are pretty short.
I'm running in CV mode.
I normally convert to arcs as much as possible but I would like to get the same smooth motion with line segments if possible. Not sure if it is a settings issue or a CPU issue or if "that is just how it is" issue.

Thanks
Derek

[cncdrive]

The UCCNC cuts up the arcs to line vectors using the tolerances you setup and then executing them as small line segments,
so an arc should have no worse tolerances as your CV setup tolerances.
In other words the arcs are also line segments ,lots of small lines when executed and the arc path is processed using the same tolerance parameters as when processing line vectors.

And at the end of the process the arcs are sent as small line segments, time frames to the motion controller, just like the lines, the motion controller do not see arcs only lots of very small line vectors.

[Derek]

The UCCNC cuts up the arcs to line vectors using the tolerances you setup and then executing them as small line segments,
so an arc should have no worse tolerances as your CV setup tolerances.
In other words the arcs are also line segments ,lots of small lines when executed and the arc path is processed using the same tolerance parameters as when processing line vectors.

And at the end of the process the arcs are sent as small line segments, time frames to the motion controller, just like the lines, the motion controller do not see arcs only lots of very small line vectors.

I remember you saying that on CNCzone. There is a definite pause at certain points.

Here is a straight approach to a 180 degree arc then a straight departure all in line segments. Units are inches.

Code: Select all

10 G00 Z0.6688
N11 X1.7274 Y-0.1245
N12 G01 Z0.4834 F60.00000
N13 G01 X1.7122 Y-0.1250 F80.00000
N14 G01 X1.1422
N15 G01 X1.1178
N16 G01 X1.1173 Y-0.1290
N17 G01 X1.1122 Y-0.1690
N18 G01 X1.1034 Y-0.2190
N19 G01 X1.0897 Y-0.2790
N20 G01 X1.0814 Y-0.3090
N21 G01 X1.0724 Y-0.3390
N22 G01 X1.0625 Y-0.3690
N23 G01 X1.0515 Y-0.3990
N24 G01 X1.0399 Y-0.4290
N25 G01 X1.0222 Y-0.4694
N26 G01 X1.0130 Y-0.4890
N27 G01 X0.9922 Y-0.5303
N28 G01 X0.9645 Y-0.5790
N29 G01 X0.9322 Y-0.6296
N30 G01 X0.9045 Y-0.6690
N31 G01 X0.8722 Y-0.7105
N32 G01 X0.8303 Y-0.7590
N33 G01 X0.8017 Y-0.7890
N34 G01 X0.7822 Y-0.8082
N35 G01 X0.7522 Y-0.8365
N36 G01 X0.7222 Y-0.8624
N37 G01 X0.6922 Y-0.8864
N38 G01 X0.6622 Y-0.9092
N39 G01 X0.6194 Y-0.9390
N40 G01 X0.5712 Y-0.9690
N41 G01 X0.5422 Y-0.9855
N42 G01 X0.5168 Y-0.9990
N43 G01 X0.4822 Y-1.0164
N44 G01 X0.4222 Y-1.0426
N45 G01 X0.3796 Y-1.0590
N46 G01 X0.3322 Y-1.0747
N47 G01 X0.2722 Y-1.0915
N48 G01 X0.2122 Y-1.1046
N49 G01 X0.1822 Y-1.1099
N50 G01 X0.1522 Y-1.1144
N51 G01 X0.1153 Y-1.1190
N52 G01 X0.0622 Y-1.1232
N53 G01 X0.0022 Y-1.1250
N54 G01 X-0.0578 Y-1.1235
N55 G01 X-0.1153 Y-1.1190
N56 G01 X-0.1478 Y-1.1150
N57 G01 X-0.1778 Y-1.1106
N58 G01 X-0.2078 Y-1.1054
N59 G01 X-0.2378 Y-1.0993
N60 G01 X-0.2678 Y-1.0925
N61 G01 X-0.2817 Y-1.0890
N62 G01 X-0.3278 Y-1.0762
N63 G01 X-0.3796 Y-1.0590
N64 G01 X-0.4178 Y-1.0443
N65 G01 X-0.4540 Y-1.0290
N66 G01 X-0.4778 Y-1.0184
N67 G01 X-0.5168 Y-0.9990
N68 G01 X-0.5378 Y-0.9879
N69 G01 X-0.5713 Y-0.9690
N70 G01 X-0.6194 Y-0.9390
N71 G01 X-0.6626 Y-0.9090
N72 G01 X-0.7017 Y-0.8790
N73 G01 X-0.7178 Y-0.8661
N74 G01 X-0.7478 Y-0.8402
N75 G01 X-0.7709 Y-0.8190
N76 G01 X-0.8017 Y-0.7890
N77 G01 X-0.8378 Y-0.7506
N78 G01 X-0.8678 Y-0.7158
N79 G01 X-0.9045 Y-0.6690
N80 G01 X-0.9278 Y-0.6358
N81 G01 X-0.9456 Y-0.6090
N82 G01 X-0.9645 Y-0.5790
N83 G01 X-0.9878 Y-0.5380
N84 G01 X-0.9978 Y-0.5190
N85 G01 X-1.0178 Y-0.4792
N86 G01 X-1.0400 Y-0.4290
N87 G01 X-1.0625 Y-0.3690
N88 G01 X-1.0778 Y-0.3221
N89 G01 X-1.0897 Y-0.2790
N90 G01 X-1.1034 Y-0.2190
N91 G01 X-1.1136 Y-0.1590
N92 G01 X-1.1173 Y-0.1290
N93 G01 X-1.1178 Y-0.1250
N94 G01 X-1.1378
N95 G01 X-1.7078
N96 G01 X-1.7274 Y-0.1247
N97 G00 Z0.6688
N98 G00

Here is the same move with an arc.

Code: Select all

N10 G00 Z0.6688
N11 X1.7274 Y-0.1245
N12 G01 Z0.4834 F60.00000
N13 G01 X1.7122 Y-0.1250 F80.00000
N14 G01 X1.1422
N15 G01 X1.1178
N16 G17
N17 G02 X-1.1178 I-1.1178 J0.1248
N18 G01 X-1.1378
N19 G01 X-1.7078
N20 G01 X-1.7274 Y-0.1247
N21 G00 Z0.6688
N22 G00

Any Ideas on why this would be happening? Like I say the arc is smooth as silk.

[cncdrive]

Hi Derek,

We will check your example code to see what is exactly happening, will probably need a few days to do so,
but I'll update you in this forum thread as soon as we will get to it.

[Robertspark]

Would it be useful for posters with issues to upload their *.PRO files so that you can see what their settings are?

When I use to frequent one of the other manufacturer forums it was apparent that some of the issues being experienced were setup issues and reviewing the mach3 profile *.XML file normally (sometimes?) showed up where the issues may have been.

[I'm not saying that the case here, but it may be easier to replicate the issue if you've got the steps per, accel, lookahead, linear error max, corner error max etc]

May be worthwhile putting a sticky on the forum asking posters with issues to just upload their *.PRO file at the time of posting the query (if it's motion / setup related etc).

Rob

[cncdrive]

Would it be useful for posters with issues to upload their *.PRO files so that you can see what their settings are?

When I use to frequent one of the other manufacturer forums it was apparent that some of the issues being experienced were setup issues and reviewing the mach3 profile *.XML file normally (sometimes?) showed up where the issues may have been.

[I'm not saying that the case here, but it may be easier to replicate the issue if you've got the steps per, accel, lookahead, linear error max, corner error max etc]

May be worthwhile putting a sticky on the forum asking posters with issues to just upload their *.PRO file at the time of posting the query (if it's motion / setup related etc).

Rob

Hi Rob,

Derek is our old customer, I think like 5years or so.
So, I have his e-mail address to ask for his profile (and probably I have it already somewhere in my e-mails), we probably exchanged a few hundreds of e-mails in the past about different things.
For first we will check the issue with the code he posted with a few different random settings to see if we see the issue that way,
if not then I'll ask for the profile from Derek.
Also we will check if the issue exist in the current release and if it exists in the next release, because there were already a few more optimisation done recently in the CV algorithm, so maybe the issue got fixed already, but again I will have to check to see...