Holding The Dies

Various Techniques Used To Mount Bend Tooling 

There are a few popular ways to hold/support the clamp and pressure die on a rotary draw bending machine. They all aim to accomplish the same thing. Namely, provide for a means of precision vertical alignment to the mating bend die (as needed) and be able to provide rigid support to the respective die when under bending conditions. In this article we will discuss only two of several means of holding a clamp die. 

The Round Key Style

For a single stack bender the clamp die can be supported, in part, by a round key design; see Figure 1. When a tube is being bent, the round key, attached to the clamp die holder, transmits a portion of the forces from the clamp die to the clamp die holder. Depending on the design of the round key, the clamp die may transmit a portion of the side load directly to the clamp die holder itself. It is the function of the clamp die hanger, in part, to keep the clamp die from separating from the clamp die holder when the clamp die retracts. Also, with the addition a set screw to the clamp hanger, the clamp die itself can be adjusted up and down for exact alignment with a mating bend die. This is most important with reverse interlocked tooling. This approach does allow for fast tool change overs. 



 

 

 

 

 

 

 

 

 

 

 

 

 

 

The Dovetail Key Style 

The function of a dovetail type key is similar to that of a round key. The dovetail provides for alignment and is critical in transmitting forces from the clamp die to the clamp die holder. However, unlike the round key style, the dovetail style can be adapted to multi stack benders; see Figure 2


 

 

 

 

 

 

 

 

 

 

 

This approach does not use hangers. The dies are machined to a very close tolerance allowing for the stacking of the dies on top of one another. Some dovetail designs make use of a set screw for means of vertical die adjustment. This screw, usually found below the bottom most clamp die, is adjusted 1X to position the bottom die relative to the mating bend die. Then it is left to the precision of the individual clamp dies to ensure the distance from tube groove to tube groove. 

The dovetail key style does cost more the manufacturer than the round key style. However, it is the geometry of the dovetail itself that eliminates the need for hangers and thus permits the dies to stack on top of one other; an important detail in a multi-stack bending environment. 
This approach also allows for fast tool change overs. 


About the Author

George Winton, P.E. designs and builds CNC tube fabrication equipment for Winton Machine in Suwanee, GA. He can be reached at gwinton@wintonmachine.com or 888.321.1499

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