Bending quality criteria
The requirements for quality in edges and bent parts have increased considerably in recent years. Looking back, it is hard to judge who gave the impetus for this. Was it the manufacturers who improved their machines, in order to stand out from the competition? Were sheet metal processors simply reacting to these new possibilities by raising their demands? Or did the impetus for increased quality come directly from the sheet metal processors? In either case, today there is a wealth of strategies for fulfilling specific quality criteria particularly well.
Exact angles
Exact angles are particularly important,
- when the first part is already intended to be a sound part.
- when after several bends, openings must lie precisely over each other.
- when several bends meet that will subsequently be shut.
- when several individual parts are joined together into an assembly and deviations can no longer be corrected manually.
- When the angle must be correct at the first try, bending has to be done with angle sensors.
Continuous angle
Continuous angle is a basic requirement at every edge. But particularly in the case of long bent parts, a continuous angle is not a matter of course. To avoid a deviation in the angle along the whole length of the bend, the curvature of the beam must be balanced by a crown, and possibly several measuring tools will have to be used.
Exact measurements
Precision parts with complex bends
Exact measurements are always required when a part is being built in and must fit into a space exactly, for instance when holes or threads must lie over each other exactly after bending. Exact measurements are assured by backgauges that facilitate exact positioning and attention to shortening factors.
No imprints
No imprints are desired when the bending edge is the visible edge of a facing - especially when the surface will not be covered with enamel or a similar coating. Imprints can be avoided by
- applying protective film before bending.
- using lower dies with plastic protection strips or plastic pressure pads.
- using movable jaw tools.
- not using segmented tools.
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Precise edge forms
Precise edge forms are needed when edges must have precisely-defined inner and outer radii. This is particularly critical for thin-sheet parts. For this reason, coining is the process most often used in this situation.