A: These modes of die failure are the most important, and they should be dealt with first:
- Premature die breakage;
- Premature die wash out;
- Premature die checking;
- Premature loss of dimensional integrity.
Die breakage has many causes — too many to list here. I prepared an article on the many causes of die breakage, with suggested cures, along with many other failure modes (see Forging May/June 2005, p.22).
The key is to get the total tool-life cost below 10% of the gross manufacturing cost, with reliability. Good targets are 5-6% for cold-forging dies and 7-9% for hot-forging dies. This is based on my experiences in both industries. Remember, cold-forging dies often cost much more per 1,000 parts to start with, but they should last much longer.
If the die is properly supported you may expect carbide-insert life over 40,000. For crankshaft forgings, the die life should be over 15,000, and approaching 25,000 with experience.Remember, there are many principles to be followed in designing dies for both processes. Miss one and you have a premature failure.
For more than 40 years H. James Henning held key technical positions in the forging industry, including as director of technology for the Forging Industry Association, and as president of Henning Education Services, a Columbus, OH, firm specializing in customized education and training in forging technologies.
Guidelines and recommendations offered in this column are based on information believed to be reliable and are supplied in good faith but without guarantee. Operational conditions that exist in individual plants and facilities vary widely. Users of this information should adapt it, and always exercise independent discretion in establishing plant or facility operating practice.