All About Rotary Stripping Techniques
Making sure the finished cut parts and scrap are appropriately stripped from a rotary die and routed where they need to go is crucial to the success of many rotary cutting applications. There are several primary techniques for accomplishing this, each complementary to various factors such as material type, thickness, desired speed of operation, and the final cut part’s shape, complexity, or size.
Male Female Knock-out: With this technique, the die cut web stays intact and travels across a slider plate to a roll with a male element synchronized with the scrap, pushing all scrap out of the web as it passes under the roll. An optional next step with this technique involves the male roll pressing the scrap into a female lower roll cavity, supporting the web more securely during the stripping process — this option works best for low-speed, still materials.
Pin Stripping: A pin-mounted to a roll or anvil cylinder skewers the scrap, pulling it out of the web and around the roll. The scrap-laden pin then passes through a comb that removes the scrap. Depending on the application, the scrap merely falls away from the force of gravity or is vacuumed away. This technique is most at home with high-speed operation and dense materials.
Vacuum Die Stripping: By applying a vacuum to pull scrap through cavities in the die and into the internal body of the cylinder and out through a hollow journal, Vacuum die stripping cleanly but relatively slowly removes all scrap. This technique is suited best for low-speed operation with thin materials where delicate handling is a must.
Can Ejection Stripping: In cam ejection stripping, the die cavity is straight-walled, allowing it to grip the die cut material securely to the die while the rest of the cut web rolls off. An internal cam then ejects the cut part after rotating away from the web. Cam ejection works best for low-to-medium speed operation with smaller die cuts.
Vacuum Anvil Stripping: As the die cut web proceeds straight out from the die cutting tangency, a pattern of vacuum ports in the anvil hold the cut scrap piece to the anvil surface, rotating the scrap out of the web. Further, in the rotation, the vacuum automatically pauses (or even reverses) to release the part from its surface. This technique works exceedingly well with thin plastic and paper materials.
Square Bar Stripping: In this technique, the die cut web and scrap matrix both proceed out of the die on to a conveyor and the scrap matrix is turned upward and away from the die cut part at a sharp right angle while the part travels along the conveyor. Thin materials, paper, and plastic and low-to-medium speed operation are perfect for square bar stripping.
Male Female Die Cutting with Self Cleaning Anvil: One of the more complex techniques, here a male punch shears against a female cavity to perform the die cut. The female cavity then traps the freshly cut parts until enough have accumulated to fall free into an open relieved area. At this point, the parts can be mechanically pushed out of the relieved area, or vacuumed out. You’ll see this technique used most often with very small parts, regardless of operating speed.
Talk to Us About Rotary Stripping Techniques!
As the industry leader in die-cutting, Bernal offers expert help and customized systems feature any number of these techniques depending on your unique goals and objectives. Our engineers are happy to work with you in choosing the best stripping technique for your specific project.