I have a helical part we use for auger flighting that we have cut and pulled by an outside vendor. We offset a surface and then used Flatten Surface to create a flat pattern dxf for the vendor. Now they are asking us to increase the outside and inside diameters of the flat pattern by 3-1/2" so the part will be the correct diameter when pulled. We think they are incorrect, but maybe not. Can anyone see that we are wrong on our flat pattern?
Paul,
That is interesting. No surprise that a SW doesn't work as we are led to believe it does. Unfortunately getting the proper tool (software) around here is out of the question. But even with the differences you showed it is no where near a 3-1/2" difference like the vendor is suggesting.
Maybe someone has ExactFlat or BlankWorks and can show another solution?
..and. yeah, the SW edge values seem reasonable? (image)
Won't the method of fixturing/clamping/pulling make a big difference in the areas where there will be plastic deformation? Would be interesting to see a video of how the form this, if they are bumped or pulled. My mind cannot help but think of seeing how vertical TMR auger flights are pulled. IIRC they like to twist a little as they are pulled so they wind up closing in, then the formed part might be almost a full turn but the flat had a ~30 degree missing. That might explain why they are asking for it to be so much larger, but I'm not sure.
What about the other direction? Since flattening seems unreliable, what about simulation of the forming process? I don't know much about FEA but isn't there a solver type that does large deformations well. I think implicit, and non linear; don't need contact or dynamic. Might be worth hiring that as a service to get you close I don't know if that would be cheaper/faster than "empirical analysis".
Just some thoughts.
Paul, thank you for running this through Rhino it is interesting that we have been able to send flighting before without problems and they want that big of a change this time.
Ben, This time it is only a smaller 20" diameter flight that I think is bump broken. We do actually do pull some of our larger TMR augers but send most of our stuff out. Normally you would expect the vendor to want to make their own flat pattern when given the finished dimensions due to the differences in deformation due to methods like you mentioned. For some reason, not this time. And, we have not been that far off when we have pulled our own flights either.
Jim,... each tool which does the interpolations using flatten is different using preset parameters (so, estimates, not very accurate)..
I would think a tool with parameters more aligned with the material/grain/process would be better suited?
I ran this through Rhino using Unroll and UV flatten.. and here are the differences.