Conceptual Design of Dovetail Joint
Some solutions to the challenge posed by Steen Winther are presented: impossible dovetail joint?
Each one starts their attempt from a particular situation, which can lead them to first find a solution (such as the rectilinear one) and later others (such as the circular ones).
What this tutorial intends is to show the style of conceptual thinking that allows "discovering the rules behind particular cases" to conclude that all possible solutions actually derive from "the same idea".
Note: this type of challenge is useful for those who do not know the solution or other similar cases. The idea is to force the process of generating and evaluating ideas. Once you know the case, the opportunity to discover solutions is lost!
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Step 1: The Steen Winther challenge
Can you design the internals in a way so that these two blocks can be taken apart and put back together again?
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Step 2: First solution: rectilinear
First solution obtained by giving great importance to the assembly. In order to be able to mount and dismount, the system should have a preferred direction for movement...
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Step 3: Second solution: circular
Second solution derived from reflecting on the preferred direction of assembly and disassembly, to discover that it does not necessarily have to be straight...
To make the cuts on the faces identical to the straight case, it is necessary to individually adjust the radii of each of the points that define the dovetail:
That is to say, that the sketch with which the cut by revolution is made has a completely asymmetric dovetail drawn, such that, when projected onto the faces of the cube, they are identical to the dovetails of the rectilinear case.
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Step 4: Generalization of circular solutions
It is simply a question of understanding that the value of the radius can be any, as long as the cut section is projected on each face, generating apparently symmetrical dovetails...
Beyond the initial "creative" stage, which offers the first ideas generated. The potential of the later "rational" stage, which takes those ideas, understands them and associates them to generate new ones, is enormous.
Some will be "particular cases" of the already generalized ideas. But others could be "genuinely disruptive" and break the mold of the previous ones. None of this is achieved without creative-rational effort and several iterations between both types of thinking.
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Step 5: Reflection about the rectilinear case
When testing with circular shapes of increasing radius, it is concluded that the rectilinear case is part of these solutions (when the radius tends to infinity)...
Sooner or later ideas begin to associate, improve, and "free themselves from self-imposed limitations." For example, if you arrived at the rectilinear solution... at some point you will think that it can be done in both directions:
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Step 6: Purely rational search
Reflecting on the circular and rectilinear cases leads us to think, what happens when the radii are very small?
It quickly emerges that there is a set of small radii (all of them centered on the original square) that are capable of generating projections onto the faces of the cube with the same look as symmetrical dovetails!
The assembly and disassembly mode is achieved by turning the pieces and then separating them:
For this purpose, the tips of the piece in yellow must be of such a size that they do not interfere with the piece in green when they are in a rotated position (mounting/dismounting position).
From the first ideas, the associations between them generate other possible solutions that, perhaps, could not be seen at first glance, such as the following one that uses a back and forth movement, with a twist, in order to separate both blocks:
Or this other solution, which forces the dismount through a spin, first without height change (to avoid interference between blocks) and then with height change (using spiral cams):
Conclusion: the conceptual search for ideas starts from points that are very personal, dependent on the knowledge and experience of each subject. However, it is important to try to rationalize and generalize the solutions. This, in some cases like this example, leads to finding "the rule behind particular cases". Finding "rules" instead of just "particular cases" is a very important skill for conceptual design.
Where did you start?
What solution first emerged in your mind?
How did you continue your creative process?
Were you able to find new solutions?
Were you able to relate the solutions obtained?
All this is very important to me (I try to investigate the creative process). I will greatly appreciate your opinion!
