Composites

 

Project Description:

 

This weekŐs assignment was to make something out of a composite, a fiber in a matrix. We were given burlap and a mostly plant based resin. I was unsure of what to make this week when I ran into Zach, a Math professor at Tufts, who I often see at the coffee shop. We had once had a conversation about helping kids visualize math concepts, and equations. I asked him if there were any functions he would like modeled. He got up, walked over to the register, and came back with a calculus book. He requested a hyperbolic paraboloid ( Z = X2 – Y2), I agreed.

 

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(googles rendition)

 

 

Modeling:

 

I asked him if he had any software that could create a .stl of it. He used mathmatica to produce an .stl of the function but when I imported it to any of my mesh handling softwares it showed up as a lineÉ

I knew that antimony had a function operation that allowed you to make solids from functions, but had never used it. I opened it up and showed Zach, neither of us could figure out what the notation was. I went in to the lab and asked Daniel how to use it. He got very excited and exclaimed, ŇItŐs Reverse Polish Notation!Ó at first I was even more confused, then he explained what it was. ItŐs where the operator comes before the term it is operating on. So X+Y is represented as +XY. This become more complicated as your function becomes more complicated. Additionally the Antimony engine has itŐs own notation for handeling certain functions like numbers and squares. There is a cheat sheet for this notation in the scripting window of the function box.

 

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More info about polish notation (I donŐt think its reverse in this case):

https://en.wikipedia.org/wiki/Polish_notation

 

More info about how to use this feature in Antimony can be found in Appendix A of Matt KeeterŐs thesis:

http://cba.mit.edu/docs/theses/13.05.Keeter.pdf

 

The equation Z = X2 – Y2 represented in the notation for Antimony is –Z-qXqY. I wanted to add a coefficient so that it wouldnŐt have such extreme angles. To add a coefficient of .5 the function was –Z*f.5-qXqY. Later I would learn that I could do all the Z scaling with the fab modules.

 

 

 

Exporting.

 

At first I exported the shape as a .stl, when I put it in fab modules it had wayyyyy tooooo many triangles, it also had the sides of the model, which I did not want because then the tool path would try to cut it out. Daniel recommended I export as a height map, I didnŐt realize this workflow was an option!

 

Here is my Antimony work.

 

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Height map as exported from top view in Antimony:

 

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The black border created sides of the surface, similar to the problem of the .stl so I trimmed it down.

 

Description: Macintosh HD:Users:NedlamAdmin:Desktop:HowToMake:Composite:MVSurface3.png

 

 

Creating the tool paths:

 

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Check out the stacked Hyperbolas

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Finishing cut step over to high.

 

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Finishing cut 2nd attempt lower step over

 

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Everything prepped before the glue up.

ŇNothing like the high drama of a glue up!Ó

 

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I may have cut my first bag while opening packageÉ

Second bag.

 

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The perforated release layer was poor quality!!

The layer and batting got stuck to my work piece!

 

 

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Trimed up and flipped over.

 

 

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Things I learned / You should look out for

á      Antimony uses Polish notation for functions

á      You can use the fab modules to do z-scaling of height maps.

á      Antimony can export a height map.

á      Fab Modules can read a height map and generate a 3D tool path from it.

á      Make sure you have a small enough stepover for finishing cut

á      Make sure you have everything ready and laid out in work place before mixing the epoxy

á      Be careful opening the bag containing vacuum bag

á      Use good quality release layer.