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发表于 2008-11-19 13:17:33
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Forming and Adjusting Sequence
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We often have to make a bend to a specific requirement, either an angle or a height. When we have tight tolerances to deal with we will need to consider spring back and variation in material. To do this we often need to design the tooling with two stations: The first station to make the initial bend and the second station to adjust the bend. With this sequence we have only two choices: 1. Make the bend so that it is less than required and make the adjusting station so that it can increase the bend, or continue the bend in the same direction. 2. The first station can over bend the part and the adjusting station will adjust the bend by pushing it back in the opposite direction of the first station. In these two methods the second is method is preferred over the first. Over bending and pushing back will give you much better and more stable results. This will allow you to hold tighter tolerances and make fewer adjustments during production. , B; q( y5 |* W
; O- {/ L u XThis forming-adjusting sequence has another advantage as well which I’ll try to explain. If beam “A” is bent up and adjusted up, and beam “B” is over bent up and adjusted down, and now both beams are at the same angle. We might think that they will function the same, but they will not. If we were to now deflect both beams “A” and “B” down by the same amount then release them, beam “A” will return to a slightly lower position than where it started. Beam “B” will return to the position that it started from. Beam “B” will always return to a higher position that beam “A” after the initial deflection. Its important to understand the when deflecting the beams it is easier to deflect back towards the direction that the beam came from. Beam “A” was adjusted to its final position by bending up and then was deflected back down. Beam “B” was adjusted down (from a higher, over bend position) and then deflected down. Beam “A” is likely to take a permanent set after its first deflection, while beam “B” is likely to keep its position. Therefore even though both beams measured the same after forming and adjusting, beam “B” will appear to have higher forces than beam “A” simply because beam “A” took a permanent set after the first deflection and is then lower that beam “B”. |
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