Carrier Corporation, Tyler, makes thousands of the "U" shaped beat exchanger tubes each year. To keep the walls of the heat exchanger tube from collapsing, a "ball mandrel" was inserted part way into the tube before it was bent around a circular die. The process had many drawbacks. The mandrels were expensive and the steel regularly destroyed the mandrel. The lubricant oil used cost $500/week, plus added costs for disposal. The process was difficult to control and therefore had a high scrap rate.
The solution is to add wrinkles to the tubes, much like hospital soda straws with a wrinkled section. A mandrel is still used to keep the tube walls from collapsing when it first starts to bend, but the mandrel is now made from hard plastic and costs $10 instead of $400. The new buuet-shaped die around which the tube is bent has grooves cut into it every half-inch. As the tube is bent, the metal actually begins to flow like a very thick liquid and fits in the grooves that forms the wrinkles, which relieves the stress that builds up as the tube bends. Equipment to perform this process was purchased from Eaton Leonard Corporation in Carlsbad California.
The new method totally eliminated the use of expensive lubricants and therefore its disposal.
Details of Reductions
Additional Information :
Scrap costs are greatly reduced as well as tooling costs and machine repair, cost savings are over $100,000 per year.