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3D modelling part 2

After meticulously recording information and measurements using production prototype 2 as a guide, I set about modelling the final piece in Form Z. (Not really a program i would recommend for this, however, it is all i have to choose from at this time).

The aim is to achieve an accurate model from which i can derive formers (to be CNC cut), and model the front and back brackets; mirror them, and have them rapid prototyped. This process ensures accuracy throughout the piece, enabling it to come together at the end.

But alas, if only it were that easy. After a week of modelling, problem solving and number crunching... the brackets cannot be resolved in a 3-dimensional space. Their form, though so simple to me, is too complicated for the program. Or rather i should say; I have designed these forms as though 'for craft', when in fact, to access these technologies is to design for the technology. This would mean considering the processes needed to arrive at a form - one is limited by the medium, in this case, the parameters of the program. In craft it is that of the material itself.

I have worked at length with those i know who can help me. However it is the same problem. I am sure a professional in this field could achieve what i want quite readily. However, this is a luxury that i can not afford.

And so, without throwing these forms away, i have opted for something a little more tradition - pattern making. I will attempt to sculpt a master model by hand of both left and right front and rear brackets. These i will send away for casting. My only hope at this point is that i have enough time to do so.

The separation of an idea from the reality is well illustrated in the development of the Vitra chair Vegetal, designed by the Bouroullec brothers. While both the concept and the reality are valid - they are two very different things. The development of this chair was very costly and drawn out for this reason. Perhaps there is a parallel to my chair here? There is, however, no comparison in cost and resources...

#honours #production chair #3D Modelling #3D #3-Dimensional curves

Backrest

3D Ply

In developing the back rest for my production chair, I have utilized the 3D Veneers I purchased earlier in the year.

This design was a response to the backrest of the previous prototype (where the top and bottom edges would dig in). The shape is derived from the woven backs I have produced in the past which provided even and comfortable support.

The former was hand shaped from Radiata Pine; edges were rounded for use in the vacuum bag.

Veneers were laid with the same grain direction throughout. A total of 5 veneers were used, resulting in a thickness of 6mm. 3 were initially glued with polyeurethane, while the final 2 were adhered using epoxy to increase rigidity. Subsequent versions will use only epoxy.

The final result (after glue-up) was strong (stiff) both horizonally and vertically, however, was prone to twisting (diagonal force). For the next version, i will alternate the grain direction of the veneers. The 3-dimensional curve seems gentle enough that this shouldn't cause any problems.

The new form is more ergonomic and now better matches the seat due to the dialogue that is produced through the 3-dimensional curves.

#3-Dimensional curves #3D veneer #bac #backrest #chair #chair #epoxy #formers #glue-up #honours #polyurethane #seat #vacuum bag #vacuum bag #vacuum forming #production chair #production P2

Into 3 Dimensions...

My post "3D modelling and experimentation" touched on some issues i was having with production chair, made apparent through crunching the numbers in 3D modelling software.

One of which was the angle at which the back members met the backrest. After bringing the back legs closer together, they appeared even closer together which emphasised the problem.

I think i have the solution. Yes i was avoiding 3-dimensional curves due to the added handwork required to produce them however i do believe this is a good compromise and it didnt take me too long at all.

I have cut the back members away at an angle, gluing the waste material on the opposing side. The effect: it essential moves the sections further out, also placing them on an angle which helps them meet the backrest. I also enjoy the look - i think it adds a nice dynamic.

#3-Dimensional curves #chair #honours #production chair #prototype #production P2

3D modelling and experimentation

I have built up a general model of my working prototype in Form Z, following the key form and dimensions of the piece.

When the numbers are finally crunched, a difficult problem comes to light. The dimensions of the chair are shaped by its function: with this 'crossover' as it is, rear members meet the backrest at an odd angle that seems impossible to fix without going down the road of 3-dimensional compound curves. This is something I have avoided as it furthers the piece from small-scale production.

The 3D model also allowed me to play around with some variations. Pictured are a few noteworthy examples which I will most likely be implemented in a second prototype:

When placed higher, the sweeping underbelly tends to disguise itself under the seating surface - having the stretchers meet the front legs at a higher point doesn't look half bad, giving the chair more lift and dynamic.

By angling the sides - bringing the back legs closer together, the chair tends to better sympathise with the form of the seat and backrests/stretchers. A successful deviation.

For the sake of simply trying it, I placed the backrest members on the outside of the back legs (after bringing them together). This was an obvious mistake, but one which can now be shown in the event I'm asked why I didn't try it.