M Fold
Extract from Pop-Up Design and Paper Mechanics • By Duncan Birmingham • Published by GMC Publications
About
Pop-Up
This mechanism, made from one piece of card, is best understood as a triple V-fold. It is a very useful shape as it raises an array of six planes and nine gullies, all of which can be extended or used to raise additional pop-up shapes.
You Will Need
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Step 1Take half a sheet of A4 card for the pop-up.
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Step 2Fold the card in half.
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Step 3Fold an angled crease in it.
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Step 4Unfold the card and cut away a wedge from the centre – below the point where the three creases meet.
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Step 5Fold up one of the sides.
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Step 6With the side folded up, fold it again – this secondary fold (*) should be angled up and away from the central crease.
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Step 7When the piece is folded out flat, these new creases should look like an arrow pointing towards (but not touching) the centre.
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Step 8Repeat, making similar folds on the other half of the piece.
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Step 9Cut four gluing-tabs below the fold lines at the bottom of the piece.
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Step 10Thoroughly crimp each crease. On this version of the mechanism there are only two Valley-folds (‘V’), one on each side of the central fold, all the others are Mountain-folds (‘M’).
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Step 11
To establish how they will lie when in the closed position, fold the whole piece into a concertina shape.
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Step 12
GLUING: follow the method used for Foundation Shape 2. Before gluing, experiment with the position on the page of the two central tabs, tight in close to the spine, or further out at a wider angle. The different positions create very different shapes.
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Step 13Start by gluing the central tabs.
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Step 14Glue side A, fold the pop- up piece into its closed position, put glue on tab B and shut the base so that tab B finds its correct symmetrical position.
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Step 15
Glue the two side tabs, one at a time. Fold tab C into its closed position, flat against the pop-up, apply glue, then fold the base shut so that tab C finds its natural position.
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Step 16
Repeat for tab D.
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Step 17M-fold variations
10.1
The two outer planes on each side of the mechanism can be configured to point backwards instead of forwards. In this case the four outer creases (two on each side of the central fold) are Valley folds. -
Step 1810.2
On this variation the bottom of the pop-up piece has not been cut to form four gluing-tabs which can be stuck down behind the body of the pop-up. Instead two large tabs are left, these have to come forward and glue to the base in front of the pop-up. This can be useful if Counter-folds are being added to the front of the design.
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Step 1910.3
This variation uses an Asymmetric V-fold (see Foundation Shape 5, to form the central body of the mechanism. The two sides are constructed as for shape 10.
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Step 20M-fold theory
The most common formula for the angles on an M-fold is very straightforward:
A=A, B=C,D=E
The central angles A and A follow the rules that apply to V-folds.
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Step 21In all the examples illustrated here the outer angles B and C match, or mirror, each other.
This is the most common form of the mechanism.
Usually, as in all these examples, angles D on
the pop-up and E on the base are also the same as each other. -
Step 22
ADJUSTING THE ANGLES TO CHANGE THE SHAPE
Some designs break away from the basic symmetry – either to swing an outer pair of planes in towards the centre, or backwards away from it. This is the formula:
To swing the outer planes inwards:
Add the same amount (x) to both B and D so that they become bigger than C and E. B = C + x, D = E + x, i.e. B = 70 ̊, C = 50 ̊,
D = 130 ̊,E = 110 ̊,x = 20 ̊.To swing the outer planes outwards, the formula
is reversed. The same amount (y) is added to both C and E so they become bigger than B and D.
E = D + y, C = B + y, i.e. E = 130 ̊,
D = 110 ̊, B = 60 ̊, C = 80 ̊, y = 20 ̊.
