Here is a technique that I discovered sometime during late 2015-2017, which I will call the "cupboard fold spacer." It creates a small gap in a unit, for example one in the center-line of a Sonobe Unit. To do this, one dimension of the paper for the unit is elongated. Then the ensuing extra length of paper in the center is pleated in half. The layers at the sides of this pleated section are peeled apart a little to create a gap in the unit (no rips required).
I originally discovered this cupboard fold spacer fold, or "spacer fold" while trying to modify my Clovery Cube (top photo of Fig 6), which is made of 12 Sonobe-type units. When folded as I originally diagrammed it in 2015, this model becomes somewhat distorted at the corners. The intention of the modification was to reduce or eliminate the crowding among the units which caused the distortion. The technique presented in this article can be applied to other units, Sonobe-type or not, or maybe even single-sheet models. One reason for sharing this technique is so that other origami designers might be able to incorporate it into their original models or units.
In this article I will first place instructions for a standalone spacer fold. Therefore, there will be an empty square on either side of the area of interest. Next, there will be an explanation on how you might apply the technique to a Sonobe-type unit, or any models or units that begin with a cupboard fold. Next, there will be an example usage for the technique. Finally, there will be a few bonus activities.
Applying to Various Units
In the sample unit folded in the instructions (which is not really a unit, only a pair of blank squares), the complete crease pattern can be divided into 3 parts:
When the square paper was cut into a rectangle, it was elongated, creating area B. Area B is in addition to areas A and C, which are both half-squares. As we have seen in the instructions, the square paper needs to be cut into a rectangle in order to obtain the area with which to make the spacer fold, which creates the layers that can be peeled apart.
Suppose we have a Sonobe unit with reverse folds (see fig. 2). Let this be the unit to which we would like to add a spacer fold:
To do this, let's first divide this crease pattern into areas D and F.
If we are adding the spacer fold to the center-line of the unit, you could take figure 1 and substitute areas A and C for areas D and F, respectively:
Once the spacer fold is made, you can finish folding the crease patterns of areas D and F. The result will be the Sonobe unit with a spacer fold in the center.
Example Usages
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If you have a Sonobe model with corners that are distorted for whatever reason, you may try the cupboard fold spacer technique. One reason for the distortion might be more layers or points at the corners than at other places in the unit. This unevenness might make the center-lines of the units crowd with those of other units. Having a spacer fold at each of the center-lines could assuage the crowding. See Fig. 6 for an example.Bonus Activities
- Using the information given in this article, see if you can fold the model pictured on the right.
- As of this writing I have only tried the cupboard fold spacer technique on Sonobe-type units. The reader is encouraged to try this technique on other types of units and maybe even single-sheet models.
- In the sample unit in the instructions, the trapezoid from the spacer fold is on the side of the unit with the slit made by the cupboard fold. This would probably be an impediment to folding many (Sonobe-type) units (unless you would not mind having the trapezoids on the outside of the finished assembly). The reader is encouraged to try to change the folding pattern so that the trapezoid would end up on the closed side of the cupboard fold.