1. Hey guyz. Welcome to the All New Phlatforum!



    Sign Up and take a look around. There are so many awesome new features.

    The Phlatforum is a place we can all hang out and

    have fun sharing our RC adventures!

  2. Dismiss Notice
Welcome to The Phlatforum PhlatPrinter III

Problem with simple rectangles

Discussion in 'SketchUcam Bugs' started by sgk, Jan 24, 2014.

  1. sgk

    sgk New Member

    Offline
    Messages:
    2
    Trophy Points:
    1
    I am having trouble using SketchUCam to generate gcode for a very simple graphic, the sideways "L" shown below:

    [​IMG] L.png
    (I picked this shape as a test because it is simple enough so that it's easy to write the appropriate gcode by hand, but it still has a little asymmetry so it can be used to see the effects of orientation.)

    The figure consists of two rectangles:
    a) Rectangle A with dimensions (delta-x, delta-y)=(100,10), and
    b) Rectangle B with dimensions (delta-x, delta-y)=(10,30).
    When I placed Rectangle B next to Rectangle A, I "healed" the combined surface by removing the part of the vertical border that the two rectangles had in common.

    In the process of composing this little graphic, a peculiar feature of Sketchup became apparent: the Dimension Box does NOT report (delta-x, delta-y) as one might expect, but (length, width). Thus, the values in the Dimension Box for Rectangle B were (30,10). This peculiarity seems germaine to the result I am reporting below.

    I made 3 attempts to get the gcode for this shape from SketchUCam:
    1) I used the "centerline" tool. This produced complex output that did not trace the entire L-shaped path, as shown below: L-centerline.png

    2. I used the "fold" tool. This produced a path that *almost* traced the L-shaped path, but skpped the corners, as shown below.
    L-fold.png

    3. Finally, I remade the L-shaped figure, in such a way as to "fool" Sketchup into allowing me to specify the dimensions of Rectangle B as (delta-x, delta-y) rather than the native (length, width). Tlo do this, I first drew Rectangle B as a short, wide rectangle with approximate dimensions of (delta-x,delta-y)=(length,width)=(12,5).
    Then I modified the values in the Dimension Box to be (10,30). This actually worked, and Sketchup produced the same L-shaped figure I'd had originally. This time, when I used the "centerline" tool to create the gcode, the output was correct and simple, as shown below:
    L-centerline-fakeout.png

    The bottom line is that "fooling" Sketchup doesn't seem like a robust technique for generating correct gcode. Unless I'm using the SketchUCam tools incorrectly (very possible, I'm both a Sketchup and SketchUCam newbie), it seems to me there's a bug in the centerline tool somewhere.
     
    sgk, Jan 24, 2014
    #1
  2. swarfer

    swarfer Moderator Staff Member

    Offline
    Messages:
    808
    Trophy Points:
    28
    Location:
    Grahamstown, South Africa
    The centerline tool is for doing, um, centerlines. This is usually an open figure, often a single line, and usually only partial depth ie not used for cutting through the material to result in a detached shape. The fold tool is a special case of the centerline tool in that it will automatically shorten the selected cutline by a small amount so as to create a valid cut line. A partial cut through the foam will result in a foldable line, as for an aileron hinge.

    Now, to cut out the shape you want at the size you specified, you actually want the tool to travel around the outside, offset by half the bit diameter. The tool for this is called the 'outside cut' tool, second icon from the left in the toolbar. This will draw a new cutline around the outside of the correctly formed (1) shape, and you can then add tabs to this cutline using the tab tool.

    Similarly, for cutting a shape of a given size out of the inside of a part, use the 'inside cut' tool.
    Make sure you set the correct bit size before you start creating cut lines.

    There are some instructional videos that may help you get up to speed on using Sketchup with SketchUcam.
    they are in this thread

    Your shape with a cut line drawn around it with the 'outside cut' tool
    [​IMG]
     

    Attached Files:

    swarfer, Jan 25, 2014
    #2
  3. TigerPilot

    TigerPilot Well-Known Member

    Offline
    Messages:
    1,578
    Trophy Points:
    48
    I want to add to swarfers excellent description that the green segments in the picture he posted are the tabs that you use to prevent the cut piece to fall away. To make it you use the tab tool, the fourth icon in the SketchUcam tool bar.

    BTW, you can use the tab tool only on inside and outside cut lines. Not on center lines or fold lines.
     
    TigerPilot, Jan 25, 2014
    #3
  4. sgk

    sgk New Member

    Offline
    Messages:
    2
    Trophy Points:
    1
    Thank you for your help. The information was very useful.
     
    sgk, Jan 25, 2014
    #4

Share This Page