Slic3r 0.9.1 - excessive steps

Hi,

I have just upgraded from 0.8.4 to 0.9.1 and when printing a single walled calibration piece noticed that the axes juddered a lot when moving. They still followed the correct line but it was almost as if they zig zagged along it with very shallow movements. Looking at the G code confirmed this:

Here is the 0.8.4 gcode sample for one complete revolution of the piece:

G1 F1200.000 E-5.00000
G1 X88.509 Y98.993 F4200.000
G1 F1200.000 E5.00000
G1 X88.895 Y98.879 F300.000 E0.00360
G1 X108.875 Y98.864 E0.17862
G1 X109.456 Y98.976 E0.00529
G1 X110.007 Y99.509 E0.00686
G1 X110.121 Y99.895 E0.00360
G1 X110.136 Y119.875 E0.17862
G1 X110.024 Y120.456 E0.00529
G1 X109.627 Y120.929 E0.00553
G1 X109.100 Y121.123 E0.00501
G1 X100.817 Y121.125 E0.07405
G1 X88.918 Y121.123 E0.10639
G1 X88.341 Y120.907 E0.00551
G1 X87.993 Y120.491 E0.00485
G1 X87.879 Y120.105 E0.00360
G1 X87.864 Y100.125 E0.17862
G1 X87.976 Y99.544 E0.00529
G1 X88.454 Y99.049 E0.00615
G1 F1200.000 E-5.00000

And here is the same gcode for the piece but with 0.9.1:

G1 F1200.000 E-5.00000
G1 X88.199 Y99.214 F4200.000
G1 F1200.000 E5.00000
G1 X88.981 Y98.800 F300.000 E0.01718
G1 X89.196 Y98.967 E0.00528
G1 X89.378 Y98.800 E0.00479
G1 X89.588 Y98.967 E0.00522
G1 X89.774 Y98.800 E0.00485
G1 X89.980 Y98.967 E0.00515
G1 X90.170 Y98.799 E0.00491
G1 X90.373 Y98.966 E0.00509
G1 X90.567 Y98.799 E0.00497
G1 X90.765 Y98.966 E0.00502
G1 X90.963 Y98.799 E0.00503
G1 X91.157 Y98.966 E0.00496
G1 X91.360 Y98.799 E0.00509
G1 X91.549 Y98.965 E0.00489
G1 X91.756 Y98.799 E0.00515
G1 X91.941 Y98.965 E0.00482
G1 X92.152 Y98.800 E0.00521
G1 X92.333 Y98.964 E0.00475
G1 X92.549 Y98.800 E0.00526
G1 X92.725 Y98.964 E0.00467
G1 X92.945 Y98.800 E0.00532
G1 X93.118 Y98.963 E0.00460
G1 X93.342 Y98.801 E0.00537
G1 X93.510 Y98.962 E0.00452
G1 X93.738 Y98.801 E0.00542
G1 X93.902 Y98.961 E0.00444
G1 X94.135 Y98.802 E0.00547
G1 X94.294 Y98.960 E0.00437
G1 X94.531 Y98.802 E0.00552
G1 X94.686 Y98.959 E0.00428
G1 X94.927 Y98.803 E0.00557
G1 X95.078 Y98.958 E0.00420
G1 X95.324 Y98.804 E0.00562
G1 X95.471 Y98.957 E0.00412
G1 X95.720 Y98.805 E0.00567
G1 X95.863 Y98.956 E0.00403
G1 X96.117 Y98.806 E0.00572
G1 X96.255 Y98.954 E0.00394
G1 X96.513 Y98.807 E0.00577
G1 X96.647 Y98.953 E0.00385
G1 X96.909 Y98.808 E0.00582
G1 X97.039 Y98.951 E0.00376
G1 X97.306 Y98.809 E0.00587
G1 X97.431 Y98.950 E0.00366
G1 X97.702 Y98.810 E0.00592
G1 X97.824 Y98.948 E0.00357
G1 X98.099 Y98.811 E0.00596
G1 X98.216 Y98.946 E0.00347
G1 X98.495 Y98.813 E0.00601
G1 X98.608 Y98.945 E0.00337
G1 X98.892 Y98.814 E0.00606
G1 X99.000 Y98.943 E0.00327
G1 X99.288 Y98.816 E0.00611
G1 X99.392 Y98.941 E0.00316
G1 X99.684 Y98.817 E0.00616
G1 X99.784 Y98.939 E0.00306
G1 X100.081 Y98.819 E0.00621
G1 X100.176 Y98.937 E0.00295
G1 X100.477 Y98.820 E0.00626
G1 X109.088 Y98.875 E0.16711
G1 X109.786 Y99.199 E0.01493
G1 X110.073 Y99.846 E0.01375
G1 X110.200 Y99.981 E0.00359
G1 X110.033 Y100.196 E0.00528
G1 X110.200 Y100.378 E0.00479
G1 X110.033 Y100.588 E0.00522
G1 X110.200 Y100.774 E0.00485
G1 X110.033 Y100.980 E0.00515
G1 X110.201 Y101.170 E0.00491
G1 X110.034 Y101.373 E0.00509
G1 X110.201 Y101.567 E0.00497
G1 X110.034 Y101.765 E0.00502
G1 X110.201 Y101.963 E0.00503
G1 X110.034 Y102.157 E0.00496
G1 X110.201 Y102.360 E0.00509
G1 X110.035 Y102.549 E0.00489
G1 X110.201 Y102.756 E0.00515
G1 X110.035 Y102.941 E0.00482
G1 X110.200 Y103.152 E0.00521
G1 X110.036 Y103.333 E0.00475
G1 X110.200 Y103.549 E0.00526
G1 X110.036 Y103.725 E0.00467
G1 X110.200 Y103.945 E0.00532
G1 X110.037 Y104.118 E0.00460
G1 X110.199 Y104.342 E0.00537
G1 X110.038 Y104.510 E0.00452
G1 X110.199 Y104.738 E0.00542
G1 X110.039 Y104.902 E0.00444
G1 X110.198 Y105.135 E0.00547
G1 X110.040 Y105.294 E0.00436
G1 X110.198 Y105.531 E0.00552
G1 X110.041 Y105.686 E0.00428
G1 X110.197 Y105.927 E0.00557
G1 X110.042 Y106.078 E0.00420
G1 X110.196 Y106.324 E0.00562
G1 X110.043 Y106.471 E0.00412
G1 X110.195 Y106.720 E0.00567
G1 X110.044 Y106.863 E0.00403
G1 X110.194 Y107.117 E0.00572
G1 X110.046 Y107.255 E0.00394
G1 X110.193 Y107.513 E0.00577
G1 X110.047 Y107.647 E0.00385
G1 X110.192 Y107.909 E0.00582
G1 X110.049 Y108.039 E0.00376
G1 X110.191 Y108.306 E0.00587
G1 X110.050 Y108.431 E0.00366
G1 X110.190 Y108.702 E0.00592
G1 X110.052 Y108.824 E0.00357
G1 X110.189 Y109.099 E0.00596
G1 X110.054 Y109.216 E0.00347
G1 X110.187 Y109.495 E0.00601
G1 X110.055 Y109.608 E0.00337
G1 X110.186 Y109.892 E0.00606
G1 X110.057 Y110.000 E0.00327
G1 X110.184 Y110.288 E0.00611
G1 X110.059 Y110.392 E0.00316
G1 X110.183 Y110.684 E0.00616
G1 X110.061 Y110.784 E0.00306
G1 X110.181 Y111.081 E0.00621
G1 X110.063 Y111.176 E0.00295
G1 X110.180 Y111.477 E0.00626
G1 X110.125 Y120.088 E0.16711
G1 X109.801 Y120.786 E0.01493
G1 X109.098 Y121.125 E0.01514
G1 X88.912 Y121.125 E0.39174
G1 X88.214 Y120.801 E0.01493
G1 X87.800 Y120.019 E0.01718
G1 X87.970 Y119.800 E0.00537
G1 X87.800 Y119.622 E0.00476
G1 X87.969 Y119.400 E0.00542
G1 X87.801 Y119.226 E0.00470
G1 X87.968 Y119.000 E0.00546
G1 X87.801 Y118.830 E0.00463
G1 X87.968 Y118.600 E0.00550
G1 X87.802 Y118.433 E0.00457
G1 X87.967 Y118.200 E0.00555
G1 X87.802 Y118.037 E0.00450
G1 X87.966 Y117.800 E0.00559
G1 X87.803 Y117.640 E0.00443
G1 X87.965 Y117.400 E0.00563
G1 X87.803 Y117.244 E0.00436
G1 X87.964 Y117.000 E0.00567
G1 X87.804 Y116.848 E0.00429
G1 X87.963 Y116.600 E0.00571
G1 X87.805 Y116.451 E0.00422
G1 X87.962 Y116.200 E0.00575
G1 X87.805 Y116.055 E0.00415
G1 X87.961 Y115.800 E0.00579
G1 X87.806 Y115.658 E0.00407
G1 X87.960 Y115.400 E0.00583
G1 X87.807 Y115.262 E0.00399
G1 X87.958 Y115.000 E0.00587
G1 X87.808 Y114.865 E0.00392
G1 X87.957 Y114.600 E0.00591
G1 X87.809 Y114.469 E0.00384
G1 X87.956 Y114.200 E0.00595
G1 X87.810 Y114.073 E0.00376
G1 X87.954 Y113.800 E0.00599
G1 X87.811 Y113.676 E0.00368
G1 X87.953 Y113.400 E0.00603
G1 X87.812 Y113.280 E0.00359
G1 X87.951 Y113.000 E0.00607
G1 X87.813 Y112.883 E0.00351
G1 X87.950 Y112.600 E0.00610
G1 X87.814 Y112.487 E0.00342
G1 X87.948 Y112.200 E0.00614
G1 X87.816 Y112.091 E0.00334
G1 X87.946 Y111.800 E0.00618
G1 X87.817 Y111.694 E0.00325
G1 X87.945 Y111.400 E0.00622
G1 X87.818 Y111.298 E0.00316
G1 X87.943 Y111.000 E0.00626
G1 X87.820 Y110.901 E0.00307
G1 X87.941 Y110.600 E0.00631
G1 X87.821 Y110.505 E0.00297
G1 X87.939 Y110.200 E0.00635
G1 X87.823 Y110.108 E0.00288
G1 X87.875 Y99.912 E0.19788
G1 X88.148 Y99.323 E0.01260
G1 F1200.000 E-5.00000

You can see that as the X axis moves from ~88 to 108, in 0.9.1 the Y axis is oscillating around 98.800 over the course of dozens of moves whilst in 0.8.4 it is just a single move.

My settings are identical between versions so I do not really know what is going on. Although the job comes out OK I imagine this will eventually wear out parts of my machine and on smaller jobs will cause noticeable errors.

Has anybody else noticed this?

Thanks

Andy

This is most likely due to the bug in 0.8.4 making walls thicker so the infill was wider. Now with 0.9.1 the infill is narrower and the result is rapid back and forth.

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I do not think that is the case for two reasons:

1 - There is infill with this part, its a single walled calibration piece and I am talking about the perimeter.

2 - The model is a straight line 20mm long going from 88 to 108 (minus a small amount for the corner radii) so 0.8.4 is doing the correct thing in making one large move between these two locations with a fixed Y (~0.01mm error only) value and extruding a larger amount compared to making lots of tiny moves between 88 and 108 whilst Y varies by up to 0.1mm therefore causing the motors to judder.

Like I said this small error does not affect the part but will likely cause additional wear to the machine.

Should I open this as a bug in Slic3rs github?

There was a bug in Slic3r where it would remove long curves during simplification, my best guess is that the fix for that stopped the simplification working in this case
I haven't looked at the actual slicing algorithm in slicer, but the oscillation along the axis looks odd unless it's trying to do infill.
It's probably best to opena bug on github, Sound doesn't read this forum very often.