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Phlat 3D - raster cutting alternately cuts in wrong dirn.

Discussion in 'SketchUcam Help' started by transistor, Sep 17, 2011.

  1. transistor

    transistor New Member

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    First let me congratulate the various contributors to the Phlat 3D / SketchUCam scripts. I've built a 3D machine and mounted my router on it. Running LinuxCNC / EMC2. Workflow is Sketchup 8 -> Phlat 3D -> Check with 'Plot G Code' -> Import into EMC2 and run. It's fantastic. I've made some test cuts on polystyrene and wood.

    Problems with 3D
    Here's a test piece I created.

    and here's the G-Code plot. (I've stripped it down to single pass for clarity. In practice I ran 3mm per pass.)


    1. The test piece I created has a number of pockets on the top surface. The generated G-code took a short-cut between the pockets. I got a groove between the various pockets.

    2. The code cuts the timber both on the Y+, away from the origin in the green axis direction, and the Y-, way back, incrementing the X/Z position after each pass. This means that the cutter is cutting properly in one direction but reverse on the alternate pass. In my example the left side of the groove was quite poorly finished whereas the right side was very cleanly cut.

    3. The whole workpiece is skimmed on each pass even if all cutting has been completed in that area. In my example the right side cutting is much more shallow and so there's no need to cut further once the required depth has been reached.

    I appreciate that making the scripts smarter adds hugely to the complexity so I'm not complaining. Just wondering if anyone else has a workaround. Maybe for 3D milling we need a different approach in the long run to allow tool changes and, for example, spiral pocketing, outside edges, etc.

    I've looked at HeeksCNC and found that the milling tools were good but that the CAD was weak in comparison with Sketchup. (Still, not bad for a one-man project.) If anyone has a good workflow for Sketchup 8 (free) to HeeksCNC then I'd be interested in having a look.

    Many thanks. Attached files [​IMG] [​IMG]
     
  2. TigerPilot

    TigerPilot Well-Known Member

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    The cutting of a groove between pockets is a problem that I have too, especially with the center line too. Try making each pocket a group by itself, after you made the phlatlines. Please report back if it works for you.
     
  3. transistor

    transistor New Member

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    Hi Yoram. I don't understand how to use PhlatLines on a 3D part. What I'm doing is
    • drawing the part
      • hitting the 'Generate PhlatBoyz G-Code' (green arrow button)
      Menu -> Plugins -> Plot GCode.
    I tried grouping each pocket individually (see screenshot below - 4 groups) but it generates the same G-Code.

    I've never used the CenterLine tool.
    Could you explain what you mean by "after you've made the phlatlines"?
    Thanks. Attached files [​IMG]
     
  4. kram242

    kram242 Administrator Staff Member

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    This is interesting. Maybe you could try to ungroup the pockets and lower the part on the z axis (blue) by say 1/16 and see how the phlat3D handles it.
    Looks like a bug to me. Maybe Jovian can shed more light on this one.
    Thanks for letting us know transistor
    Mark and Trish
     
  5. Jnida63

    Jnida63 Member

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    did you make sure the safe z setting is more than your piece of foam?
     
  6. TigerPilot

    TigerPilot Well-Known Member

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    With the 'phaltlines' I meant the inside line, outside line, fold line, center line and tab. You must have done them if you where able to generate the g-code. Explode the groups that you've made, make the phlatlines and then group each part.

    I know it's a pain in the neck but, as I mentioned it before, it is a bug in the SketchUCam script. It's a real pain if you have a part with a lot of center-lines. You have to group each line, almost, to prevent the cross-over cut, where it should have risen to the safe height but didn't
     
  7. TigerPilot

    TigerPilot Well-Known Member

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    Jeff, I'm not sure what you mean by that. You set the material thickness, which I hope he did, and the safe height. But even if he didn't set the material thickness, it would cut only as deep as the material thickness is set to, plus the overcut percentage,and that's it. It still shouldn't make the cross-cut.

    Unless, of course, he didn't set the zero z-point to the material surface.
     
  8. Jnida63

    Jnida63 Member

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    Heck if i know what is happening :D I am just throwing ideas out ;)
     
  9. transistor

    transistor New Member

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    Thanks for all the interest, chaps. I've figured out that the problem is related to the model height and the specified material thickness.
    Here's the model file which looks like this:


    Note that the model is 29.0mm high.
    If I set Material Thickness to 29.1mm I get this G-Code plot:


    but if I set it to 29.0mm I get this:

    Note that in this plot the tool takes a shortcut from one pocket to the next. It doesn't lift clear of the material. This may be a problem with number precision between Sketchup and the script.

    So, does this help us understand what's going on and what approach should I take to solving the problem? Specifying that the material is a little thicker than it actually is will result in the cutter skimming the whole surface, taking the finish off it and greatly increasing the job time so that's not a great idea. Attached files [​IMG] [​IMG] [​IMG] test3forumA.skp (70.8 KB)Â
     
  10. 3DMON

    3DMON Moderator Staff Member

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    Yoram, he is using the Phlat3d part of Sketchucam. This is the 3d side of Sketchucam and has nothing to do with the centerline tool like your thinking.
     
  11. Jnida63

    Jnida63 Member

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    Wow, i was right!!!
     
  12. kram242

    kram242 Administrator Staff Member

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    :doubleup:
    Good job guyz!
    Mark and Trish
     
  13. TigerPilot

    TigerPilot Well-Known Member

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    Oops!!! :oops: :oops: :oops: Look me up in the corner, I'm the one with the Duncan cap. :oops:
     

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