To Summerize

At the outset of this research we aspired to familiarize ourselves with the scripting plugin Grasshopper by attempting to design a chair capable of being digitally output, and whose ergonomic contours would be parametrically defined and adjustable. It took a number of weeks and hours of tutorials to begin wrapping our heads around the way to think in terms of grasshopper’s framework and learning the appropriate combination of components to use to achieve a desired outcome.  


In the initial stages of the project we encountered the problem of rationalizing ergonomic characteristics in terms of functions that we could feed into grasshopper. We struggled with how were we going to devise a set of relationships in grasshopper that would adjust curvature of seat and seat back in response to a persons width and height. We decided to approach the chair in section, drawing seat and back at an angle of 104 relative to one another, an optimum number considering the ergonomics of a lounge chair. We then set a series of points along the sectional spine, and assigned curves to those points, perpendicular to the sectional spine, that would serve as the seat sections. At this point we had to decide how to determine the curvature of the seat sections and how their curvature would be parametrically driven.  


Our initial instinct was to assign a cosine function, which is similar to the dish shape of a seat, to the seat section curves. By applying a domain and range function to the cosine component, we were able to isolate the concave portion of the cosine wave, which allowed us to adjust the depth and width of the wave while keeping it’s period constant.  


After multiple iterations we came to the realization that using a quartic polynomial equation (x4+1=0) as a means of generating seat base in section, we could adjust the parameters of the equation to create a variable ergonomic seat base and seat back. Over the course of this project we both realized that the way in which we had set up our script indicated that were using grasshopper more as a means of generating ergonomic form, and not as a means of responding to ergonomic form as we had set out to do. From this realization we have come to understand the importance of an intent and methodology when using parametric modeling tools.


Although we were not left with a ergonomically responsive chair, nor a 1:1 product, we both 
feel extremely confident and comfortable using grasshopper after attempting this sketch problem.  
We are optimistic about future success using grasshopper as we continue to explore its capabilities 
with our thesis projects.


Until Next time...
-nick + Max

Possible Iterations

detail of possible assemblage to reduce racking

Option 1: infill between ribs at seat back top and lower legs

Option 1: rear view

Option 2:  Alternating cuts for infill

Option 2 : Rear View

Proto-TYPE

Over break we output a  1/2 Scale proto type of our chair model using grasshopper.  It was made from 1/4" Mahogany. 

Testimonial: WOW! Thats comfy.  

Our Chair is ready To Output

rendering of chair: Exploits both waffling and stacked contouring

Using Grasshopper to generate surfaces for the seat and base, we baked it into rhino.  In rhino we offset the surfaces and contoured them.  From this model we were able to create a laser cut file in cad.  After laying out the pieces we model them to check for continuity and any discrepancies.  Here are a few snap shots of what the final chair should look like, however we have made some slight modifications as to how the edge of the seat will look (no exposed rib ends).

Tomorrow we are outputting our chair at 1/2 scale.  It will roughly measure 15 inches tall.  It will be constructed out of 1/4" MDF and cut using the lasercutter.

Chair Rendering: Note the language of bent planes, one clearly defining the base and the other clearly defining the seat.

Using Formulas to Generate a Base for Our Seat surface

Screenshot: Seat with Base

If cosine lends itself for deriving a desired seat section could a similar formula lend itself to creating a seat base?  We asked ourselves this question hoping to find an equation that could possible play the role of both seated surface and as a support.  After reverting back to high school algebra II/trig we were reminded that formulas with Asymptotes were similar to the section of our seat base.

Several attempts to finding a formula that would be appropriate for representing the points that defined our seat base brought us to polynomial functions.

A quartic function (x^4) has the right number of degrees necessary for providing the section we needed.  We once again used this formula with number sliders attached to the variables associated with this function to the derive the base height and width. 

Screenshot: Entire Script

Screenshot: Seat base Script

Now that we have a seat base using the x^4 function and a seat surface using a CosX function, it is important that these two surface will be able to intersect in a manner that will allow them to share curvature.   Our next step is to go into the Seat portion of our script and replace it with the X^4 function so that the two separate surface will have the same curvature at the place where they overlap.

Once we have successful achieved this we should be able to output this chair at 1/2 scale and then finally at 1:1.

Aligning Sections to Normals

In tour previous script version our cross-sections were not aligned to the normals of the seat profile section.  We were able to go into our exiting script and rotate the frames based on their relative angles.

Screen shot: Entire Script

Rotating the curves to normals

more editing of seat surface

Elevation showing the frames rotated to normals

Rotating each plane normal to the curve of the  section makes the shape of the seat surface smooth and minimizes irregular geometries when baking out form into rhino.

Outputting our first Prototype

Screenshot:  Rhino, Contoured surface

Lasercut file

Can the CNC become a frame or Armature?

What are the least amount of material needed?

fully assembled chair

Cardboard Chiar @ 1/4 scale