Comparing Rotary Pre-shear to Flying Die Post-cutoff Systems for Stud Lines
Hill Engineering/Formtek Inc. has designed and built rotary punching machine systems, rotary shear machine systems and flying die punching and cutoff machine systems in roll forming machine lines for over 60 years. It is our experience that when you have a product line consisting of many different widths and the same formed dimensions, such as with Stud lines for instance, it would normally pays to run the line as a pre-cut system with a servo-driven rotary shear. The rotary pre-shear is designed to cut off the widest blank to make your widest stud. Therefore, there is no change-over time required for the cutoff when changing the stud width such as is necessary when using a flying post-cutoff die!
On top of the flexibility of running with a servo-driven rotary pre-shear you can also achieve high speeds for high production requirements. These lines are fed with a powered straightener/feeder unit which is tied electronically into the servo-drive of the rotary shear machine. The rotary shear starts rotating on demand as the closed loop encoder unit measures the length and tells the servo-drive to rotate up to speed and shear. The material is engaged in the roll former and after shearing is done, the lead end of the coil continues to be fed into the roll former which is running slightly faster than the straightener/feeder and takes over pulling the material and the cycle repeats.
Different lengths can be programmed into the controller so lengths and quantities can be changed without stopping the line.
Also, when pre-shearing while running Stud and Track (and Structural Channels for that matter), the roll former incorporates side angle pass (SAP) roll stations near the end of the roll former to make sure the side walls are square to the base. This guarantees that you achieve industry standard product coming out of the roll forming machine.
From this extensive experience we have found that the most efficient way of running a high speed stud line day in and day out, even with the option of punching openings at both 2 foot and 4 foot centers with a full line speed capability of 500 fpm, is to rotary pre-punch and rotary pre-shear using state-of-the-art servo-drive technology.