Assessing Variables
Once a tube end forming application is decided upon, there are many variables that will need to be assessed to deduce what tube end forming process will be the most efficient. Assessing different variables is a critical step in the deciding process for a tube end forming project as one change could have drastic effects to the overall scope of a project. In the initial stages of planning for a tube end forming project, we ask our potential customers for these specific variables so we can assess the overall impact they might have on the outcome of a tube end forming project. Here are some of the variables to consider.
Material Type
Knowing the composition of the material that will be formed is vital information for any project. Each material has its own set of challenges and variables that need to be taken into consideration. Is the material malleable? Will the material cause any spring back or memory issues? How hard is the material? How will this material effect tool life? Will tooling need to be coated? Will this material require standard or abnormal lubricant? These are variables that can be addressed once the material is known, however some materials are harder to form than others. In most cases, material type will not affect the kind of machine used, but rather the tooling and the lubrication needed.
Wall Thickness
Wall thickness also plays a big part in deciding the proper tube end forming process. Applications consisting of thicker wall tube (0.120” +) are best suited for ram end forming processes where substantial amounts of hydraulic pressure can be applied to achieve the desired outcome. Smaller applications, depending upon the form, can be completed with a segmented, ram, or rotary process. However, even with a wall thickness such as 0.065” and smaller, material type and wall thickness need to be taken into consideration.
Size & Diameter
The size and diameter of the tube can affect the overall size of the tube end forming process. Generally speaking, the bigger the tube, the bigger the process needed in terms of equipment footprint. Most manufacturers have equipment lineups that accommodate for a range of diameters with the proper tooling. Larger diameter end forming requires larger tooling which can affect tooling changeover times and efficiency.
Part or Assembly
In some cases, the part being formed in the tube end forming process is not only just a part, but is part of an assembly. If end forming is needed for an assembly, considerations for proper forming area and clearances will need to be evaluated. Depending upon the tube end forming process, custom fixtures or dies may be used to provide support or to lock the orientation of the assembly in place. The use of custom fixtures or dies supplies added safety if the machine is operated by a human element.
Part Volume
Applications for tube end forming vary, especially when it comes to part volume. Your application may call for a few hundred or 100,000+ pieces to be produced in a year. High volume production processes require fast tube end forming processes to meet volume requirements. Two tube end forming processes may be capable of producing the same application, however if high volume is a factor, the faster process should be assessed and weighed with its pros and cons.
Cycle Time
High volume production and fast cycle times go hand in hand. If high volume production is needed, the tube end forming process will require a fast cycle time. Not all tube end forming projects require a fast cycle time. However, proper cycle times should be evaluated based on the volume requirements.
Straight or Bent
If the part is bent and/or lacks a straight section of tube for end forming, the use of custom dies or jaws may be needed to complete the process. Cutting cavities within the tooling jaws or dies will allow the clearance needed to complete the end forming process. End forming close to the tangent of a bend adds more difficulty depending upon the application. Customs fixture may be used in conjunction with custom jaws and dies to ensure accuracy, feasibility, and safety. Like part assemblies, bent tubes will also need to be assessed for clearance within the end forming area.
Weld Seams
Weld seams, if improperly applied, can be a challenge for those looking to end form. If a weld seam is not welded all the way to the end of the tube, the chances of that tube splitting during the end forming process, increases. Raised or un-scarfed weld seams can cause issues since the weld seam will increase the wall thickness of the tube in a specific area. Most tooling is designed for a specific wall thickness, and if the weld seam is raised, that extra material will have to be displaced during the end forming process. This extra material can cause premature tooling wear and inaccuracies. For example, if the application was a 20° flare with a surface profile GD&T call out on the inside flare surface, it’s more than likely that the weld seam area will be out of tolerance depending upon the surface profile spec. This is because of the extra wall thickness that is harder to displace.
Tolerances
Tube end forming applications vary from simple to complex. Depending upon the application and the tolerances required, a complex tube end forming process may be required to achieve the desired results. In some cases, applications are reviewed to discuss what items are critical to part function, and if certain tolerances prove to be a bottleneck, they may undergo a design change.
Cosmetic Requirements
During the end forming process, cosmetic imperfections can be the byproduct of tube end forming. Many ram end forming applications used tube grips to hold the tube statically in the dies during high pressure end forming. While these grips do hold the tube in place, they also create serrations just behind the newly end formed part. Should the newly created grip marks be an issue, tube backstops can be used in place of the tube grips to eliminate the marks. Rotary tube end forming can cause surface finish changes and residual coining marks from the tooling. For most applications, these imperfections are only cosmetic and have no impact or effect on overall part function. Like ram end forming, rotary end forming will utilize tube grips for applications such as flares, Norma balls, and certain styles of beads. The grip marks produced by these grips are minimal since less force is applied. Segmented end forming can cause clamp or segment marks on the inner or outer diameter of the tube; however, these marks do not affect part function.
Lubrication
It’s commonplace for lubrication to be used for most tube end forming process. Many tube end forming processes require the use of a lubricant to aid with cycle times, tolerances, and efficiencies. When it comes to complex ram end forms, such as progressive fuel funnels, the use of a lubricant is almost necessary to produce a form that will meet the required tolerances. The use of a lubricant can also extend the life of the tooling as well. Coating the tooling with a lubricant creates a film which reduces the wear between the tooling, the tube, and the dies. Ram end forming processes typically have a closed loop flood coolant lubrication system that can be used. Lubrication for rotary and segmented processes is usually applied by the operator, however automated systems can be added to increase efficiency.
Process Adaptability/Machine Capability
When a tube end forming project ends, companies either have the option to sell off equipment or to retool for an upcoming project. Many machines have the capability to be retooled if the new process fits within their capable end forming range. Should the need arise for another end forming project, having the capability to retool instead of investing into new capital equipment can save not only capital but time as well since tooling is quicker to manufacture.
