Rotary Tube End Forming
Rotary tube end forming is a method that works around the circumference of a tube, either from the inner diameter or the outer diameter depending upon the application. Similar to a ram end forming method, the tube is held statically using a set of clamp jaws. In most cases, the tube is slid over the tool and as the end forming cycle progresses, a drawbar with a wedge moves forward and pushes out the tool rollers. As this is happening, the tool is spinning within the inner diameter of the tube. As the rollers spin around the diameter of the tube, they move outward until they push the material into the profile cut within the jaws. For applications like inverted beads or grooving, the tool works from the outside.
Pros & Cons
Rather than having the material cold flow into a profile for beading, rotary forming uses rollers to move the material into the jaw profile. Since the material is moved between the rollers and jaw profile, beads and flares are produced with better radii and surface profiles making it ideal for most beads and flares. In most cases, rotary end forming will produce the fastest cycle time out of the 3 methods. Most applications that utilize this method, do not need hydraulics; however, in some cases, it is necessary for proper tube grip and forming. Nonetheless, should the application not require hydraulics, the capital cost of the equipment is reduced compared to segmented and ram end forming. Tooling costs for rotary end forming methods are less expensive than ram end forming. Tooling design for rotary end forming does allows material variation in terms of wall thickness. Weld seams can still cause issues but a sudden change in wall thickness will not be as detrimental as it would be in a ram end former. Footprints for rotary end forming methods are smaller than their ram counterparts and are similar to some segmented end formers.
Rotary end formers are not without their drawbacks. While they are ideal for beading, the process of using rollers to move the material into jaw profile does cause more wall thinning than segmented or ram end forming. Wall thickness is one of the biggest variables in determining if rotary end forming is the right method for the application at hand. Rotary end formers are best suited for applications with a wall thickness less than .08” of an inch. Anything more than that and pneumatic boosters and hydraulics will have to be added to create the power needed to complete the forming process.
Beading and flaring are ideal applications for this method. However, larger beads, such as Marmon beads, are better suited for segmented end forming because of they produce less wall thinning. Knurling, inverted beads, and tube cut-off are all practical applications that can be also achieved.
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