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How to make hole in sheet metal NOT normal to surface

Discussion in 'Using Alibre Design' started by slipstick, Jun 10, 2018.

  1. slipstick

    slipstick Member

    Hello,

    I have this drawing

    upload_2018-6-10_6-2-24.png

    where the hole that penetrates the 60 deg portion is not normal to the surface. How do I do that so I don't get this- the walls of the hole are perpendicular to the surface, and they shouldn't be. Is that not model-able upload_2018-6-10_6-6-20.png upload_2018-6-10_6-2-24.png upload_2018-6-10_6-6-20.png ? Is that something best left to the 2D drawing?
     
  2. oldfox

    oldfox Senior Member

    I would draw the hole on the ?ZY? plane instead of the face of the material. Then extrude cut "through all".
    Caveat...
    I don't use sheet metal so if this doesn't work in sm then I would reconstruct as a "part", not sheet metal. Then it should work.
     
  3. oldfox

    oldfox Senior Member

    Like this...
     

    Attached Files:

  4. slipstick

    slipstick Member

    That's what I did here. I'll have to make it non-sheet metal.
     
  5. slipstick

    slipstick Member

    Yeah, I'll have to go this route.
     
  6. Oldbelt

    Oldbelt Senior Member

    New Sheet Metal Part (1).jpg

    No problem using extrude cut insted of sheet metal cut.
    But how to manufactoring this part, those skew holes is not a sheet metal operation.!!
     
    batejosh likes this.
  7. slipstick

    slipstick Member

    I don't know how the original was made - it's a drawing from a WW2 airplane. I'm guessing there was some small jig that held the bent part while the hole was drilled.
     
  8. oldfox

    oldfox Senior Member

    Then I doubt very seriously if this was a one-off job. If I was the engineer for this part, then I would have designed something like a flip-flop vise to hold the part and then have the presets set at -30, +30 and 0 degrees. I guess it could have been done an a mill or a punch press.
     
  9. Nick952

    Nick952 Member

    Use the "Hole Tool " in sheet metal, instead of the "Sheet Metal Cut"
     

    Attached Files:

  10. slipstick

    slipstick Member

    :) That's it! Cool! Thanks! I was trying to use the cut tool.
     
  11. Lew_Merrick

    Lew_Merrick Alibre Super User

    Slipstick -- Is that a (round) hole that is Punched after the strip is Formed or could it be an Obround punched before it is Formed? That would be the question I would ask.
     
  12. bigseb

    bigseb Alibre Super User

    I would draw the hole on a newly created plane instead of the face of the material. Then extrude cut "through all".
     
  13. bigseb

    bigseb Alibre Super User

    Exactly
     
  14. Lew_Merrick

    Lew_Merrick Alibre Super User

    One thing to understand is that "modern" SheetMetal tools are designed to operate on the CNC StripIt operational thesis. The idea of using closed forming dies today is anathema to many in the sheetmetal business. The CAD industry has followed their "lead." It is a shameful truth.
     
  15. Nick952

    Nick952 Member

    I would have thought that the "Sheet Metal Cut" should work in the same way as "Extrude Cut" , in that the "Cut" is done perpedicular to the Plane or Face that the sketch is drawn on and not transform from (in the above sample) the Cut sketch that is drawn on a vertical plane, acting as if the sketch had been drawn directly on the sloping face.
    After all if I wanted the hole to be perpendicuar/normal to the sloping face, I would sketch directly on the face or on a plane parallel to it!
     
  16. Lew_Merrick

    Lew_Merrick Alibre Super User

    Nick -- The point if the CNC Strippit approach is that "holes" are either punched or nibbled directly through the sheetmetal and then it is air-bent to form. No punch set-ups, no forming set-up, and little (if no) accuracy! Trimming to shape consists mostly of nibbling as well. Few today know how a Blanking Dis is calculated or made (something that was part of my first year of apprenticeship as a Tool & Die maker 50+ years ago).
     
  17. slipstick

    slipstick Member

    Without having an actual example of the original part, or some other inside knowledge, I doubt I could ever find out. It was a part of an FW 190 fighter. I don't know how the Germans routinely did things then.

    Trivia - I have found that factory drawings from both Dornier and Focke Wulf used the exact same title block. I'd bet the other manufacturers used it as well, based on that.
     
  18. Lew_Merrick

    Lew_Merrick Alibre Super User

    As somebody who served his apprenticeship under a German Machinist's Guild (my "translation") Master Tool & Die Machinist, I suspect that it was compoundly punched in a Closed Form die-set. My "suggested approach" would be that the piece was "grabbed and formed" into the (from the "open" side of the "V") and, when that "closure" was made a second "stroke" punched the holes through the angled faces. Such die-sets were not "common" in the late-1960's, but I saw and made such things. [It is hard enough today to find a machinist who knows what a tooling ball is!]
     
  19. bigseb

    bigseb Alibre Super User

    I couldn't imagine a machinist not knowing what a tooling ball is. Best referencing/setup method there is imo.
     
  20. Lew_Merrick

    Lew_Merrick Alibre Super User

    Unfortunately such people are all too common these days!
     

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