Fighting the resistance to sliding is one of the big problems constantly faced when building flying dies. Anything that can be done to lessen the resistance to movement of the die will allow the line speed to be increased somewhat without damage to the part. In this post, we'll discuss several design methods that can reduce die sliding friction depending on the size of the die.
Methods for Reducing Die Sliding Friction
With light dies (usually made out of aluminum or magnesium) and low cutoff tonnage, linear roller bearings and shafting can be used to avoid friction. Instead of the die riding on slides mounted to the bolster plate, linear bearings are attached to the die, and these bearings ride over hardened shafting mounted to the bolster plate.
For medium-sized die cutting on high-speed lines where rapid acceleration is necessary, one method used to lessen friction is to let the die roll on a series of rollers (pins) trapped in a cage. Unlike receding rollers or air bearings, these rollers keep rolling to reduce friction even during the cutting cycle when most dies try to come to a halt, if only for a split second.
On large dies or on dies that require a lot of tonnage to cut off, the method used to reduce friction is a receding roller bearing. The bearing is small but only has to bear the weight of the die and none of the actual cutting tonnage. This fairly inexpensive method of floating a heavy die uses the same size bearing, bearing retainer, and spring retainer for all sizes of dies. Variations can be adjusted the spring and its preload to suit the die weight. The bearings roll on the existing slides with no alteration of the slides.
Die Return Systems
It is impossible to talk about dies without covering die return systems too. Die return springs are still the simplest and probably most widely used return system. However, with more complex, heavy, high-speed lines in use every day, the air cylinder return becomes more necessary. It provides a more positive and, most of the time, a faster return system.
By using an air return triggered by an air valve of some kind, the line can usually be run faster and sometimes more accurately. The trick is to shut the side of the valve off that is holding the die back once the die is in the rest position. Usually , some residual pressure to hold the die back. This eliminates the worry of the cylinder return valve being too slow to release the die in time to allow the die to travel out with the material.
Reducing die sliding friction in roll forming is critical for ensuring the longevity and performance of tools and equipment while maintaining product quality. Effective strategies for addressing die sliding friction include selecting appropriate lubricants, optimizing roll tooling design, and implementing proper maintenance practices. These approaches not only enhance the efficiency and precision of the roll forming process but also minimize wear and operational disruptions. By adopting these solutions, manufacturers can achieve improved productivity and extend the lifespan of their roll forming systems.