Understanding 'First Cut' in Lamination Pro

Discussion in 'Segmented Turnings Forum' started by David Muehlbauer, Sep 11, 2019.

  1. David Muehlbauer

    David Muehlbauer PRO Member

    I have designed a bowl in Segment Pro with a Feature Ring. I designed the Feature Ring in Lamination Pro, but 'First Cut' doesn't work the way I understand the term. The Segment Edge Length I need is 2 3/16" (aka 2.385"). So if I used one-half of that for the 'First Cut' in Lamination Pro, and a 30° angle, the segment width says 2.5", but that isn't what happens. If I measure 1 1/4" along the edge of the laminated strip and cut my 30° angle with my miter saw my chevron is not going to be 2.5" wide because I am angling the two slices before I glue them together. By doing my own calculations I determined that I have to cut it 1 5/16" to get a chevron 2 1/4" wide. The larger the angle, the longer the slice needs to be.

    What am I missing here? I am not a math wizard but it seems that in Lamination Pro, changing the angle should either change the First Cut or change the Repeating Unit.
  2. mfisher

    mfisher Super Moderator Staff Member

    If I am reading things correctly in SP you have a featured ring that has a Segment Edge Length (SEL) of
    2 3/16. Which is close to 2 1/4 SEL
    In LP you are setting a first cut at 30degrees. I set a first cut of 1 1/8 inches. That will produce a repeating unit of 2.25"
    In the image LP Question 1 you can see the settings of 30 degrees and first cut of 1 1/8 inches.
    In image LP Question 2 is the results of selecting Gen 1. It shows the repeating unit (chevron created will be 2.25 inches in width. The Laminate board should be almost 30 inches to allow for 20% extra.

    Hopefully that clarifies the math in a round about way.

    Attached Files:

  3. David Muehlbauer

    David Muehlbauer PRO Member

    Thank you for the reply, but I probably didn't word my question as clearly as I should have. On the attached drawing, it appears that 'First Cut' refers to 'A', the width of the actual slice. But when I cut this on my miter saw, I need to know 'B'. I was able to figure it out with a little geometry, but it seems like the software should include this number, because the width of the slice is the result of making the 'B' cut. I had previously used another software product and it provided both numbers, and that was frankly more helpful.

    Attached Files:

  4. mfisher

    mfisher Super Moderator Staff Member

    My guess is it is B. My trig memory is pretty old. If I set the first cut at 1" in the software it does not matter the cut angle. The repeating unit will be 2" inch. Why, the lines are parallel. So when you make the first cut and measure each strip with the calipers it should be 1". When the pairs are put together it should be 2.

    When designing in LP one needs to look at the repeating unit and make it as close to the SEL as possible. I tend to overbuild. That is my rings are built a bit larger than the final. Therefore my strips are wider to allow for the waste.

    If you really need to know the math behind LP, please contact Lloyd.

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