Segmented Tube End Forming: Machine Types & Applications

Unlike rotary or ram tube end forming, segmented tube end forming is the use of tooling segments that can either work from the ID or the OD of a tube, and sometimes both. Segmented tube end forming is an ideal process for various kinds of tube sizing, reducing, beading, and re-rounding which depends upon material type, size, wall thickness, and other variables that need to be considered. Not all segmented tube end forming is the same. As aforementioned, some equipment offers both ID and OD operations. Throughout the tube and pipe industry, there are three main types of segmented tube end forming equipment that are primarily used, which all serve different functions and applications. 


I/O Sizers 

I/O sizers (inside/outside) operate by using inner and outer segments that work from the inner and outer diameters of the tube. These sizers excel at re-rounding tubing due to the inner and outer segments working in tandem. The inner and outer segments expand and reduce the diameter of the tube which breaks the memory within the material. Once the memory is broken the tube stays at the final size it’s sized to at the end of the forming cycle. Aside from re-rounding, simple beads and slip fit reductions/expansions are also possible with this type of machine. The expansion and reduction capability range on I/O sizers are limited due to the short travel of the tooling (typically slip fit only)The forming depth is also short due to certain design limitations of tooling. Some versions of I/O sizers have part rotation to minimize possible parting lines that can be formed if the segments repeatedly form the same spot. Tooling changeovers vary from manufacturer with some being as quick as drop in tooling and others requiring 5-10 minutes to change out.  


I.D. & O.D Sizers 

Similar to I/O sizers, I.D. & O.D. sizers utilize inner or outer segment but never have them both in the same tool set. Rather than using both sets of segments, most I.D. & O.D. will come with 1 or 2 stations for end forming. If the machine has two stations, one can be set up for expansion while the other is setup for reduction. Due to the lack of other segments, these sizers have the benefit of having better expansion and reduction ranges than their I/O counterpart. Forming depth is also increased, with some equipment having the capacity to form as far as 8 inches from the end of the tube. While these machines do excel at expanding and reducing, re-rounding is an application better left for I/O sizers. Most machines lack part rotation, so the operator must manually rotate the part between tooling hits. The other thing to consider is the tolerance of the form.  These types of sizers don’t hold the concentricity because the segments are just expanding into free space.  Tooling changeover for most equipment is quick and efficient.   

Indexing Segmented Machines 

Like I/O sizers, indexing segmented machines use a set of inner segments, but instead of utilizing a set of outer segments, they use a set of clamps. The use of clamps instead of outer segments has many benefits. Because of the clamps, the tube is held in place throughout the end forming cycle. This clamping process drastically improves concentricity of the product compared to other methods. Beads and other profiles can be cut into the clamps and the inner segments can be used to form high tolerance beads and other end forms by moving material into the profile. Rather than pulling material from one end of the tube, indexing segmented machines pull material from both ends. This process of forming beads and other end forms produces minimal wall thinning compared to other tube end forming methods. After each expansion, the segments retract, rotate, and then expand again to move other areas of material and to eliminate the possibility of parting lines. Out of all 3 types of segmented end forming machines, the indexing segmented machines are best in class in terms of accuracy, wall thinning, and concentricity. These machines are ideal for high tolerance Marmon beads and Norma balls. Expansions as far as 1” on diameter are also possible. Re-rounding of the tube is possible with certain models because of the OD clamps and ID segments. 

This video example above showcases a Proto-1 ISM-6 tube end forming machine forming a 5″ spherical marmon bead. The tooling can be seen (video effects used, the clamp stay in place during the whole auto cycle) expanding and rotating as it expands the bead. For more videos of our segmented equipment, check out our website or our YouTube Channel or Segmented Video Playlist

Closing Thoughts 

Segmented end forming is a viable solution for those who are looking to produce Marmon beads, Norma balls, single or double beads, expansions, or reductions. Knowing your application and cross referencing it with the pros and cons of each machine type will help narrow down which segmented end forming process is best for you. Proto-1 is an OEM of tube end forming equipment for the tube and pipe industry. We have full line ups of ram, rotary, segmented, and tube deburring machines. We also strive on custom application and adding automations to help with the difficult application.  If you have any question regarding segmented end forming or other forms of tube end forming, please contact us today.