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Slow Arc after Pp in Fusion360

Discussion in 'CAD' started by Denko, Nov 24, 2020.

  1. Denko

    Denko New
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    Hey guys

    Just wanted to quickly ask if anyone had the same issue? Arcs run pretty slow for me after post processing them with the latgest OB Post processor. Lines go pretty well, but some arcs are just slow and noisy.

    Looks like it produces a lot of G1, G3 movements. I tried playing with the tolerances and this min arc. stuff in the Pp, but no improvement so far.

    A little part of the curve:

    G1 X11.699 Y42.957 Z0.431
    G3 X11.077 Y42.983 Z0.409 I-0.436 J-2.968
    G1 X10.702 Y42.96 Z0.396
    G3 X10.145 Y42.872 Z0.377 I0.186 J-2.994
    G1 X9.753 Y42.772 Z0.363
    G3 X9.298 Y42.616 Z0.346 I0.743 J-2.907
    G1 X8.891 Y42.438 Z0.33

    Does anyone know how to fix that?

    btw.. when I import a dxf file of the same piece in the OpenBuilds Cam, it works fine. So I assume it has something to do with the Post processor. Fusions simulation looks good aswell
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
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    Hi, I need your Fusion f3d file please.

    and BTW, messing with the arc limits is 99% guaranteed to produce WORSE results, I advise against it, it took a lot of testing to find those values that work reliably.

    your code looks like an interpolated arc, straight,arc,straight,arc, ... in very short segments, the axis with the slowest acceleration will be the limiting factor .
    have you tried turning on smoothing for that toolpath?
     
  3. Denko

    Denko New
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    Thanks for the reply! How can i send you the f3d file? So far i noticed that there are 2 smoothing values. Once for the tooplath itself and then down below there's a smoothing filter. What values should I put in there? Default looks to be 0.01mm.
     
  4. David the swarfer

    David the swarfer OpenBuilds Team
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    you can attach it here or start a private conversation with me and attach it there
    for the toolpath itself is what I would use.
    I would use 0.025mm as that is the minimum step on my X and Y axes. no point going smaller than tghe machien can do.

     
  5. Denko

    Denko New
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    Thank you! Just played around with the settings and it got a little bit better. I wonder if there's an possibility to make it even quicker around the smaller arc? FYI, i'm just testing it on the openbuilds simulator, not on the machine rn.
     

    Attached Files:

  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Rather use the machine. Sim is just visualisation, not taking any calculation of acceleration settings
     
  7. David the swarfer

    David the swarfer OpenBuilds Team
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    upload_2020-11-28_18-14-57.png
    tolerance 0.05mm (if you need the part to be more accurate than this then you have to reduce this and tolerate the extra cut time.)
    Smoothing tolerance 0.15mm

    upload_2020-11-28_18-15-25.png
    please make sure you are using the latest post
    (Post Processor : OpenbuildsFusion360PostGrbl.cps V1.0.21)

    In the post config, Reset everything to default then change 'minimum chord length' to 1mm as above. this removes those sections of
    arc,line,arc,line,arc,line that can be very slow, replacing them with just lines.
    I am surprised that the smoothing doe snot have more effect, but then this is an arc that is about the same size as the cutter. Maybe a larger cutter will change it?

    Something else I noticed.... while your cutting feedrate is 7000mm/min your ramp feedrate is 200mm/min, and since this entrire cut is a ramp except for the short bits over the tabs, it is going to cut at 200mm/min. Now 7000mm/min does seem a little fast to me unless you are running a Datron Cube (-: but do make sure you are getting what you expect in terms of feedrate.
    Code:
    (Operation 1 of 1 : 2D Kontur1)
    G54
    G53 G0 Z0
    S24000 M3
    G4 P0.5
    G0 X8.756 Y44.375
    Z15
    Z5
    G1 X8.756 Y44.375 Z3.1 F2000        ; plunge rate
    X8.763 Y44.346 Z2.915 F7000       ;cut feedrate
    X8.784 Y44.264 Z2.747
    X8.817 Y44.135 Z2.615
    X8.859 Y43.973 Z2.529
    X8.905 Y43.794 Z2.5
    X9.053 Y43.212
    X9.128 Y43.04
    X9.252 Y42.899
    X9.413 Y42.803
    X9.596 Y42.762
    X9.783 Y42.779
    X10.145 Y42.872 Z2.482 F200       ramp rate!
    X10.421 Y42.929 Z2.468
    ....
    
     
    sharmstr and Peter Van Der Walt like this.

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