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michael_mcewenmichael_mcewen OS Professional Posts: 76 PRO
I've looked at the sheet metal tutorials for unfolding boxes, etc. But, this may need a different approach.  Can anyone show me how to derive a flat part for waterjet cutting from the flexed / in tension parts in my TRUSS part studio: https://cad.onshape.com/documents/7ac2bda8403f47ec99dfd4a2/w/62ca548aab6aaa6334415bca/e/64a9ac196b4b6b4f25dcf740

The 3 "truss" arms (top, right, left) sweep parallel to the construction line in CENTERLINE TRUSS (sketch 1).  The part TOP TRUSS is simple, the curved part is already flat and relaxed. the 2 parts titled RIGHT TRUSS and LEFT TRUSS are identical, and are drawn flexed, and in tension.  I need a convert these parts into a relaxed, flat part.  

Any help will be greatly appreciated. 




  • brucebartlettbrucebartlett Member, OS Professional, Mentor, User Group Leader Posts: 2,100 PRO
    Hi Michael,  You will not be able to use sheet metal to unfold this as it is a free-form surface. the only option I can think is using a Feature Script the will unfold/unwrap it to a sketch.  I think @konstantin_shiriazdanov may have developed a feature to do this. 
    Engineer ı Product Designer ı Onshape Consulting Partner
    Twitter: @onshapetricks  & @babart1977   
  • konstantin_shiriazdanovkonstantin_shiriazdanov Member Posts: 1,171 ✭✭✭✭✭
    I beleve in this case my FS won't work because we have a shape of double curvature. Though since the length of the part is far greater then the width you can get approximate solution by measuring the length of inner and outer edges and calculating the mean value and considering the width to stay the same
  • michael_mcewenmichael_mcewen OS Professional Posts: 76 PRO
    Thanks guys, I'm afraid this is a bit over my head. If the relaxed curve can't be mapped with Onshape, do you have any alternative approaches you could suggest?  I attached some files here of an earlier model I made. The dxf files of the relaxed parts and the approach to arriving there are unknown to me, as I contracted the work out to a CAD guy I've since lost track of. In that case, I started with a hand drafted (sketch shown below) with the curve height mapped every 5".  Any suggestions will be appreciated. suggest?
  • konstantin_shiriazdanovkonstantin_shiriazdanov Member Posts: 1,171 ✭✭✭✭✭
    edited July 2018
    in Solidworks there is a feature Flatten surface for things like that
    since you are a pro user you could create an Improovement request or internal ticket, OS developers usually pay much attention to what pro users need
  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 3,930
    @konstantin_shiriazdanov flatten surface is in solidworks premium only! Took them several years and several attempts to develop so it is no trivial matter. 

    @michael_mcewen have you taken a look at ExactFlat in the AppStore?
    Director, Technical Services, EMEAI
  • brucebartlettbrucebartlett Member, OS Professional, Mentor, User Group Leader Posts: 2,100 PRO
    Unigraphic's also used to have really nice surface unfold tool, I remember using it back in about 2003 when I did have the pleasure of using the software. I don't think the SolidWorks one came in, till a few versions ago. Obviously, it can be done and I'd love to see something like this, even as an FS in Onshape or even better integrated to sheet metal for this example. 

    ExactFlat maybe a good option for now. 
    Engineer ı Product Designer ı Onshape Consulting Partner
    Twitter: @onshapetricks  & @babart1977   
  • michael_mcewenmichael_mcewen OS Professional Posts: 76 PRO
    Thanks for the tips guys. I'll look into ExactFlat, and I guess I should start an OS request ticket, right?
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