Figure 1 shows that you can choose either a full pattern or half pattern for a right segmental bend. By careful sub division of the bend angle a right bend conventionally starts and ends with a half segment (i.e. a circular entry and exit) and the sheet metal worker need only make the half pattern and then when marking out the material just has to flip the pattern over. From a manual cutting point of view that's all you need but many people have contacted me requesting if the full pattern can be drawn to send to the laser cutters without first having to mirror the half pattern in their CAD software. Version 15 beta now allows you to export the full pattern as a DXF file which saves time.
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| Figure 1 - A full segment from a right segmental bend |
Figure 2 shows that you can start the pattern from the long seam by typing a negative bend radius. If you're a sheet metal worker you'll be familiar with staggered joints and how that translates to improved nesting of the segments on the flat plate. It's not always possible to use staggered joints as you may be trying to hide the seam on the inside of the bend but you'll have to stand some waste material.
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| Figure 2 - Starting the bend from the long edge. |
Beta version 1.5 introduces a nested DXF export. From the file menu choose export nested patterns (DXF). The software will only nest the number of segments required to make 1 bend. Figure 3a and 3b show how 3 segments from a right segmental bend can be nested for minimum material quantity and no waste. The right segmental bend by convention starts on a half segment unless your connecting to an existing mitred pipe.
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| Figure 3a,b - A 3 segment right bend. a)Starting on the small seam. b) Starting on the large seam. |
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| Figure 4a,b - 6 segment oblique bend. a)No gap between segments. b)Adding a user definable gap between the segments. |
Figures 4a and 4b show that the oblique export option always starts on a full segment. You can start on a long seam similar to the right bend above if you require. It's also possible to define a gap between the segments (either right or oblique) for 2 main reasons: 1) Compensate for the kerf width of the cutting tool and 2) to stop the segments falling out in a automated manufacturing process (say)laser cutting. It's then possible to roll all the segments in one go before snipping out the tags and fettling up.
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| Figure 5a,b - Cutting staggered segments by hand |
Of course if you are cutting the segments by hand with shears then no gap is required as shown in figure 5a and you only need the 1 template to transfer the pattern to the material (say) by scribing around the pattern. Figure 5b shows that I made a more durable pattern by gluing the paper pattern to thin steel and then the 1 template allows me to draw all the curves including the long seam segments for the whole bend.