Bent parts in trimmer

Q: We are experiencing specific, bent parts after forging and hot-trimming in a platter of two, and arranged end to end. What can you advise?

... We use a nested trimmer that has a spring-loaded punch. Nitrogen springs were chosen to provide sufficient holding power, so that any tendency to bend or twist is corrected during trimming. We find that if we trim the forgings, the “b position lends to be the bent part When we reverse the platter! the same position in the trimmer tends to bend (actually, it twists). The forged parts after the final forging blow are nice and straight.

A: I have seen many modifications of nested or compression trimmers and most do a good job of ensuring that the parts are maintained straight after trimming. You should check out the nitrogen “die springs” for performance.

For example, if you do not have a tensile testing machine that could be used to measure the force being supplied by each “spring,” then you could place a simple weight or die block over each spring and then measure the movement with a dial indicator.

While this does not provide a true measure of the spring’s force, it is a method of determining if all of the springs are supplying essentially the same force. If not, the weaker springs will collapse more under the weight of the block than the stronger springs. Remember, the nitrogen springs can lose their gas level over lime or after extended use.

H. James Henning answers forgers' technical and operational questions. For more than 40 years he held key technical positions in the forging industry, most recently as director of technology for the Forging Industry Association. He is president of Henning Education Services, Columbus, OH, specializing in customized education and training in forging technologies.

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