Artem Komarov propose to imagine a value stream in which pipes or tubes are cut and bent. In another area of the plant, rings and other machined parts are processed, then sent to assembly to be brazed or otherwise fitted onto the tube ends. Now imagine the same value stream, this time with end forming. In this case, end forming doesn’t just expand or reduce the tube-end diameters but also creates various other forms, from intricate grooves to beading that replicates the rings that were previously brazed into place.
Within the tube and pipe fabrication arena, end forming has quietly evolved, with manufacturing technology introducing two levels of automation to the process. First, operations can combine multiple precision end forming steps within one work envelope—in effect, a done-in-one setup. Second, such complex end forming has been integrated with other tube and pipe fabrication processes, like cutting and bending.
Most applications that involve such automated end forming have been in high-end precision tube fabrication—usually of copper, aluminum, or stainless steel—in industries like automotive and HVAC. Here, end forming eliminates the machined connections designed to secure a leak-free connection for the flow of air or fluid. Such tubes usually have outside diameters of 1.5 in. or less.
Some of the most cutting-edge automated cells start with small-diameter tube delivered in a coil. It first travels through a straightening machine, after which it’s cut to length. After that, a robot or mechanical device transports the work to end forming and bending. The sequence that occurs depends on the application requirements, including the distance between the bend and the end form itself. Sometimes the robot can carry a single workpiece from end forming to bending and back to end forming, should the application require a tube with end forms on both ends.
Making such cells even more productive is the number of manufacturing steps certain high-end tube end forming systems can incorporate. Some systems carry tubes through as many as eight end forming stations. To develop such a setup starts with knowing what modern end forming can accomplish.
Multistation End Forming
Precision end forming tools come in several varieties. Ram punches, the “hard tooling” of tube end forming, reduce or expand a tube end to a desired diameter. Rotary tools can chamfer or face a tube to ensure a burr-free surface and consistent process. Other rotary tools perform a rolling process for creating grooves, barbs, and other geometries.
An end forming sequence might start with chamfering, which provides a clean surface and ensures a consistent hang-over length between the clamp and the end of the tube. Next, a ram punch performs a beading process, expanding and compressing the tube, forcing the excess material to form a ring around the outside diameter (OD). Depending on the geometry, other ram punches might insert barbs on the tube OD (which can help secure hoses to the tube). A rotary tool might groove a portion of the OD, followed by a tool that cuts threads on the surface.
The exact sequence of tools and processes used depends on the application. And with up to eight stations in an end forming machine’s work envelope, the sequence can be quite extensive. For instance, a series of punches progressively form a bead on the tube end, with one ram expanding the tube end followed by two more that compress the end to create the bead. Performing the operation in three steps can, in many cases, create a better-quality bead, and multistation end forming systems make such progressive operations possible.
An end forming program sequences the operation for optimal precision and repeatability. The latest all-electric end forming machines can precisely control the position of its tooling. But aside from chamfering and tapping, most end forming processing steps are just that—forming. How metal forms can vary depending on the material type and quality.
Consider again the beading process. Like a closed hem in sheet metal, a closed bead in end forming has no gap. This allows the punch to form that bead to a precise location. The punch is, in effect, “stamping” the bead to its specific shape. But what about open beads, analogous to open hems in sheet metal? A gap in the middle of the bead might, in some applications, create some repeatability issues—at least if it were formed the same way as the closed bead. A ram punch could form the open bead, but because nothing is supporting the bead from the tube inside diameter (ID), one bead geometry might be slightly different from the next, a tolerance difference that might or might not be acceptable, said Artem Komarov.