Quite often our customers ask us for bends without tangents. Mostly it is for aesthetic reasons, but often enough it is for a particular process need.
Such bends bring a special challenge. Thermoplastics’ bends, due to the requirement of secondary heating, have stresses that can lead to ovality in the bend’s arc. Usually, a small ovality is not a problem in coupling the bends, for the unheated tangents are quite round and undistorted. But there is an issue with tangents also.
Metal bends, depending upon the bending process, can have a quite visible distinction between the bend arc and the tangent. But, it is not so with thermoplastics’ bends. In such bends, tangents gradually take form. In reality, the transition space between the arc and the tangent has an increasing radius. A 24″ radius bend, thus, may have a small transition space between bend and tangent, but this space is increasing in radius from 24″ to infinity (the tangent proper). This is important, for if someone asks for a bend with a 1″ tangent, we can demonstrate the geometric place where the tangent begins, but in real space, it takes about 4″ to get a true unbent straight section of the tube for coupling.
This week we were challenged to provide a zero tangent bend of a 6″ OD 90Deg 24″ CLR tube. The goal is to put four of these together to make an illuminated circle bend.
With proper packing and mold formation we held the ovality to a very respectful 0.17%.
It will be interesting to see what the full circle looks like.