Though the necker on a can making line performs a very specialized task, the mechanical subsystems found on this machine offers a number of design lessons that can be applied more broadly by any engineer working to improve the performance and reliability of high-speed equipment.
Consider, for example, the necker’s cam-driven ram actuators. Mounted on a rotating turret and moving at speeds up to 250 strokes per minute, these rams push the round can shell onto a series of shaping dies that gradually reduce the diameter of the can to form its neck.
Traditionally, these Belvac rams have consisted of a round moving pin that translates axially within a barrel-like steel housing, with a machined keyway to keep the pin from rotating. The ram was driven directly via a pair of metal cam followers that mount on the rear end of the pin and engage a stationary cam.
That design, however, suffered from three problems in the field. For one, it required an aggressive lubrication regimen to combat ram and cam wear. For another, it allowed the pin to lift and twist in the barrel, causing premature wear that extends all the way back to the can. And lastly, the traditional design limited the operating speed of the necker.
We eliminated all three problems with a radical redesign of the ram that:
Eliminated the need for lubrication. The redesign replaced lubrication-hungry metals with lube-free polymers wherever possible. The redesign completely does away with the metal-on-metal wear between the cam and cam followers, which had been the primary failure mode with the traditional ram design.
Optimized the geometry of the ram. The redesign features a square ram, rather than round. The square ram does a far better job at managing the actuator’s on- and off-axis forces. It also guides the pin more effectively, reducing wear.
Removed moving mass. Thanks to the use of polymer components and structural aluminum, the redesigned ram weighs in at less than half the weight of the traditional round ram design. Total reduction of moving mass on a 10-stage line is nearly one metric ton.
Now in use by can makers around the world, the redesigned ram has offered a compelling payback. It has resulted in reduced maintenance costs, including the elimination of expensive automated lubrication systems. It has also contributed to reduced defect rates and faster line speeds.
Learn more about the redesign in our latest design case study, Redesign Improves High-Speed Can Making Machine. The case study offers a deeper look at our design process, including a glimpse at the finite element analysis (FEA) work that guided some of our decisions. The case study also highlights the side-benefits of designing for lubrication elimination.