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The Roll-Kraft versatile design method works very well on light-gauge, mild steel, or some higher tensile steels.
The versatile design gives more consistent tube properties, unlike other designs that can have hard and soft spots. This is a great benefit for hydroformed tubes. It also provides greater stability by providing a rounder tube when going through the fin passes. There is less buckling, and it helps remove the memory of the strip. The versatile design is the best choice for sharing breakdowns, since it works more of the strip with each pass. When sharing, it is recommended that the tube produced be no less than 80% smaller than the designed tube size.
There are many advantages to using the versatile method. Some include:
• Reduction of material springback and greater stability
• Provides a better, rounder presentation of the strip as it enters the fin pass
• Works well for hydroformed products
• Forms more of the strip with the edgeform radius
• Allows better formation of smaller sizes when sharing breakdowns
Two issues can arise when using this method, due to the aggressiveness of this forming design:
• Marking - This design is best used with a T/D ratio (thickness divided by diameter) of under 3%; using heavier gauges can cause marking
• It is important that side rolls be in place between each breakdown to assist with the forming flower
The versatile method is very useful in the industry and continues to be the choice of many companies who run multiple size tube and pipe products.