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| Figure 1 - Trapezium to Circle transformer {3D export from the STOR21beta software} |
Several users have requested a trapezium to circle transformer as shown in figure 1. Rather than release a version that can only make a trapezium to a circle, it's now possible to define the quadrilateral corners as shown in figure 2. There are 3 main types of quadrilateral: convex (A to F),concave (G) and crossed (H) as shown in figure xx. Concave and crossed are not applicable to sheet metal , or at least not a common development.
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| Figure 2 - Types of quadrilateral: A)Square, B)Rectangle, C) Isosceles Trapezium, D) Trapezium ,E)Rhombus, F)Parallelogram, G)Concave, and H) Bow tie. |
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| Figure 2a,b,c,d - Trapezoid to circle transformer |
Figure 2c shows that the circle position has been offset to create the plumb vertical side. The bend angles can become extremely complicated and this piece was made up as trial of the actual piece. Making a trial piece is often very useful to prove the pattern is OK and you can actually get it in the press. Figure 2d has the trapezium corners 'dressed up' and the paper pattern wrapped around the transformer.
STOR20 used R1 to R4 to define corner radii but this is now changed to RA,RB,RC and RD and these can be defined even when the quadrilateral is not rectangular.
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| Figure 3 - Corner radii |
From figure 3, the corner co-ordinates are measured from 0,0 and their respective sign is required. When the corners have a radius applied then the co-ordinates are the intersection of the 4 main sides where from figure 3 you can see the corner angle is divided equally between the tangents of the 2 adjacent sides. Some draughtsmen issue drawings with dims to the centre of the radii - you'll have to work out or use CAD to then find the corner intersection points. Note, each corner radius to be independently specified, as shown in figure 4.
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| Figure 4 - Independent coner radii |
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| Figure 5 - STOR21 beta screen shot defining the quadrilaterl corner co-ordinates. |
To enter the quadrilateral corners slide the properties pane over to the left (or click the trapezium tool bar button) where you can see 8 edit boxes for the corners. The corners are defined on the z plane.
I feel that entering 4 corners by co-ordinates is less intuitive than just entering the 2 rectangular dimensions therefore I've made the interface offer both options. Simply tick the square coordinates check box and the rectangular dimensions SX and SY become non-editable. You can now control each of the 4 corner vertices by entering x,y (on the z plane). Remember the offset OX,OY,OZ refers to the circle end and is measured from 0,0,0.
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