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Center Line tool still not workong properly.

Discussion in 'SketchUcam Bugs' started by steinie44, Jul 2, 2016.

  1. steinie44

    steinie44 New Member

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    When will the center line tool be fixed? I just downloaded ver 1.4a and it still is bad. Way too much Z action. I'm running a CNC Router, not a sewing machine.
    Centerline tool.JPG
     
  2. swarfer

    swarfer Moderator Staff Member

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    Please read this thread
    http://www.phlatforum.com/xenforo/t...code-for-a-contour-backwards.5406/#post-39244
    Which will give you some insight into the causes and some solutions as well.

    In brief I call this "backtracking" and it is caused by sketch up mixing line segment directions within a set if connected lines.
    There are 2 easy fixes
    1. Use the bztools 'create polyline' to fix the directions
    2. Create a small split in the line where you see it start backtacking. Then it can generate code for the left to right segments separately from the right to left segments.
    Fixing it automatically is non trivial but is on the list of things to do.
     
    Last edited: Jul 3, 2016
  3. steinie44

    steinie44 New Member

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    The video does not address the problem. I managed to get rid of most of it by using repairBL and changing the cut direction 'Overhead Gantry' repeatedly. It's still a bug and if it's "non trivial", it should be fixed!
     
  4. swarfer

    swarfer Moderator Staff Member

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    Hi

    Creating a split in the sequence as indicated in (2) above is a total fix, without having to use any additional plugins or any more thought.
    The split can be a mere 0.002" wide.
    (but not 0.001" since Sketchup is likely to rejoin the lines for you)

    The BZTools 'create polyline' function is also a total fix, it fixes Sketchups internal ordering which is the root of the problem.
    Sometimes the 'weld' plugin also fixes it.

    Changing cut direction will not, to my knowledge , make any difference at all, but might shift the backtacking to different portions of the cuts.

    Editing the lines may or may not change it because Sketchup does internal re-sequencing, sometimes, when you edit lines.

    RepairBL may have some effect, I will experiment with it shortly.

    Oddly, my link does not lead to a video, what video did you watch?

    This is not a bug. Bugs cause incorrect G-code.
    Working G-code is generated for all cutlines.
    The cuts are out of order because of something Sketchup does with it's internal storage that is unpredictable and difficult to deal with.
    Being 'difficult/non trivial' does not equal 'must be fixed' :)
     
  5. swarfer

    swarfer Moderator Staff Member

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    well, you owe me, I think I may have stumbled on the fix, look out for the new release 'coming soon' (after beta testing)
     
  6. Serge Ecoiffier

    Serge Ecoiffier New Member

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    I often had the issue of the "needling" (sewing machine syndrome), or backtracking, and, as Swarfer mentions above, it is due to some aspects of SketchUP which SketchUcam handles as best as it could. I played with this for the longest of time... Some of it was triggered by "excessive" editing of my designs interlaced with SkectUcam. Some of it is due to my using too much precision (ex: 96 segment circles rather than default of 24), etc. In other words, partly my being green as well. However, editing a design with no changes in SketchUcam, moved the backtracking around. Sometimes it disappeared. Other times it just got worse. SketchUP was moving things around which seemed to trigger backtracking. Regardless, it is definitely a pain. But there are ways to work around the issue.

    As Swarfer indicated above, there are a few tricks to minimize the backtracking. The best one to date, from my experience, is using BZpolyline The Repair/Phlaten is not as consistent in the results (my own mileage). Weld is a dice throw. Introducing tiny splits quickly becomes a pain. I use 1/64" so I can see them when zooming in and still be small enough a 1/8" bit would not leave much of a trace. But some of my design had severe backtracking - a job which should run in minutes took hours. To find the right combination of tricks often took hours, if not days. So I gave up and went with the divide and conquer approach, along with the BZpolyline 'fix'.

    I pass most of my design through SketchUcam in 3 to 7 steps : inside cutouts, outside cutouts and one or more for details (contours, etc.) One file - the master copy, is the design. Once 'clean', I make a copy for each step. Some make the copies within the same file, I prefer having a few files to juggle. This lets me control the order aspects are milled/routed by joining the individual Gcode files as I want using SketchUcam. This also lets me change certain aspects of a design (ex: customize markings on a game board) without having to regenerate the entire job. Manual tool changes can also be done this way, but each tool becomes a separate job with same X/Y zero. Just need to zero Z between tools... There's lots of opportunities with this divide and conquer approach.

    In extreme cases, I would use a Gcode editor to manually remove the backtracking. I would do a few other 'enhancements' to speed up jobs ... For example, I would not pull all the way up to the 'safe height' (SketchUcam actually does two steps on way down : rapid to just above surface and then feed into the material; where safe to do, I would pull up to just above the surface or previous cut instead of all the way up). But I love getting into these details ... OCD, sorry.

    The best news of all, Swafer most recently tweaked SketchUcam to reduce the backtracking. Testing against some of my 'trouble' files shows a great improvement. In many cases, the backtracking disappears. In other cases it reduces it substantially. In no case did it make things worse. Editing the design in SketchUp didn't seem to move backtracking around since it was reduced or eliminated.

    I'll be sticking to SketchUp and SketchUcam for a while longer, especially for 2.5D needs. True 3D work would need more ... but I'm not there yet. Do not forget, these are tools ... The user is a definite part of the magic.

    Wait for the next release of SketchUcam. I'm certain it will reduce if not eliminate your "sewing machine" symptoms.
     
  7. steinie44

    steinie44 New Member

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    Woo Hoo, Centerline tool works now with Ver 1.4d. Knocked off 1000 lines of code in a 5600 line file, for my Christmas Orniments.
     
    swarfer likes this.

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