10 Replies Latest reply on Feb 27, 2013 2:51 PM by Robert Stupplebeen

Making a hexagonal pattern on a surface

Dylan Thrush Feb 15, 2013 10:30 PM

I'm in the process of restoring an old suzuki gsx600, it came completely in peices and without front fairings or bodywork. I generally don't like the look of the fairings on the front of your general 'crotch rocket', so I was glad to have the opportunity to design my own that hang back and hug the engine and chassis. My general approuch to this build is:

-design some new fairing in solidworks out of suraces.

-export those as .stl so I can load them in pepakura (pepakura takes 3d models and flattens them out so you can print them and then re-assemble in meatspace, a poor mans prototyping)

-print out on cardstock, reassemble

-test fit, if it looks good, onward! If not, redesign.

-Once everything is good reinforce with fiberglass and make a mold.

-make actual fairings with fiberglass/carbon fiber, whatever the budget allows.

Two days in and I am still stuck on design. I could go with a general curvy aerodynamic surface, but thats WAY too easy. No I have to choose a design that will make me waste hours figuring out how to make it . Instead of curves and such I want this to be made of hexagons, kind of like this hexagonal surface, but less complex:

I basically want to design my surface with the basic shape and then convert it to look like that ^ . It can't be curvy though, I want all those hexagons to be flat. My first approach was to make the surface and then project a sketch of my hexagonal pattern on to it, then somehow see if there was a way to convert the curved sketch lines to be straight. Then use 'Filled Surface' to fill in the individual hexagons. That failed, projected curves don't like more than one open or closed sketch, and I am not patient enough to ad every single one by hand.

So, thoughts? Suggestions? Much appreciated.

Re: Making a hexagonal pattern on a surface

Robert Stupplebeen Feb 20, 2013 8:40 AM (in response to Dylan Thrush)

You can probably get a similar effect by saving out as a coarse STL but instead of hexagons you will have triangles of varying size. Unfortunately this looses one of the design goals of 'wasting hours'. This also sounds like a meshing algorithm for plate elements. Unfortunately most of those are designed for 3 or 4 sided elements. This has the upside of being able to have a similar face size. I hope this helps.
Rob Stupplebeen
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- Re: Making a hexagonal pattern on a surface
  
  Dylan Thrush Feb 20, 2013 11:01 AM (in response to Robert Stupplebeen)
  
  I had the same idea! Unfortunately it just doesn't make it coarse enough, I did just a tiny test surface and had over 4000 triangles! That's just a bit too many for my taste. On the plus side it would add plenty of wasted hours cutting out and gluing paper :) Thanks for the reply Rob!
  
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  - Re: Making a hexagonal pattern on a surface
    
    Robert Stupplebeen Feb 20, 2013 12:57 PM (in response to Dylan Thrush)
    
    There are tolerance settings for STL export or mesh seed sizes for FEA that could be tweaked to hopefully get the granularity you are looking for.
    
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    - Re: Making a hexagonal pattern on a surface
      
      Dylan Thrush Feb 20, 2013 2:03 PM (in response to Robert Stupplebeen)
      
      Yep, I played around with those. I set it on the coarsest setting I could get and still got waayyyyy too many triangles. Maybe you know how to change it differently than I do. I go 'save as' -> STL -> options -> and change it from there. Is there another way to do it?
      
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      - Re: Making a hexagonal pattern on a surface
        
        Robert Stupplebeen Feb 20, 2013 3:06 PM (in response to Dylan Thrush)
        
        In the attached picture I meshed a 10mm radius hemisphere in Abaqus. I hope this helps.
        
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        Re: Making a hexagonal pattern on a surface
        
        Dylan Thrush Feb 20, 2013 3:25 PM (in response to Robert Stupplebeen)
        
        Hmmm that looks promising, never used Abaqus, but I might just have to learn. Is it possible to make those 6 sided instead of 4? And does it scale up nicely? Thanks for the help.
        
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        Re: Making a hexagonal pattern on a surface
        
        Robert Stupplebeen Feb 20, 2013 4:28 PM (in response to Dylan Thrush)
        
        Abaqus is expensive however there are free FEA meshers out there. In my first comment I mentioned that most FEA surface meshers can either do 3 or 4 sided elements. There have been several threads on Eng-Tips talking about free FEA programs. Check out this forum http://www.eng-tips.com/threadminder.cfm?pid=727. You may also be able to access SolidWorks/Simulation (Cosmos) to get to it's mesh. And yes it scales well.
        
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        Re: Making a hexagonal pattern on a surface
        
        Dylan Thrush Feb 20, 2013 5:15 PM (in response to Robert Stupplebeen)
        
        Very cool, I will definitely be looking into FEA's, that looks like the easiest choice so far. Bummer about the limited number of sides, but I might just have to suck it up. Thanks!!
        
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        Re: Making a hexagonal pattern on a surface
        
        Dylan Thrush Feb 26, 2013 9:24 PM (in response to Dylan Thrush)
        
        Ok done some research and tried out some programs, I think I found a (somewhat) simple meathod for getting the results I wanted. First I design my surface in solidworks then save as a .STEP. Then I import it to LISA, on the inport menu I can set element size and what not. So I mesh it in LISA, but now I can only save it as a .stl, so inport to Meshlab and save as .dxf, then open in Pepekura and walla! Once I got used to it it really wasn't hard or time consuming. Unfortunately the amount of time it takes to cut out all those pieces and glue every single one is way too much for my liking. And the end result is still really flimsy, I don't think it would work too well as a mold. So failure for this application but using the Silidworks to LISA to Meshlab to Pepekura is a pretty solid rapid prototyping tool.
        I think for my original purpose I might just get some 1/8th inch steel rod and weld together a frame that is polygonized, then stretch felt over it and fiberglass, that will make a sturdy mold. Anyway thanks for all the help Robert! I hope someone else will find this helpful.
        
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        Re: Making a hexagonal pattern on a surface
        
        Robert Stupplebeen Feb 27, 2013 2:51 PM (in response to Dylan Thrush)
        
        You are very welcome. Thank you for taking the time to post your trials and conclusion!
        
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