Mandrel bending, also known as mandrel tooling, is a sub-process of tube bending. In this process, a mandrel—a metal rod or ball—is inserted into the tube while it is being bent, which creates a more precise bend with no wrinkles or kinks. For some applications, it is acceptable to have a wrinkled tube, particularly when the tube just has to function and quality is not a factor.
The process of mandrel bending provides a high quality tube because the amount of flow is improved, making the inside diameter of the tube consistent throughout, even at the bend (something that is not possible to do without using a mandrel).
Quick links to Mandrel Bending Information
Applications of Mandrel Bending
Mandrel bending is commonly used in exhaust applications in the automotive industry, pipe applications in the plumbing industry, and instrument applications in the musical instrument manufacturing industry because the process improves the look of the bend and also creates a much tighter bend than is possible with empty bending. When the mandrel is inserted into the tube, it has to be strong enough to support the tube so that it won’t be deformed during bending, but also flexible enough to ensure that the tube is still properly bent.
Materials Used in Manufacturing Mandrels
- Aluminum-Bronze Alloys
- Alloys of aluminum bronze and nickel aluminum bronze remain popular as a mandrel material. Mandrels composed of these metals work well for use with steel tubing. The mandrel won't damage the workpiece as readily as mandrels made of harder metals.
- Some types of thick-walled, strong workpiece materials may require the use of a steel mandrel. For instance, this tool proves exceedingly useful for shaping and bending non-ferrous pipes. Today, manufacturers sometimes finish steel mandrels using hard chrome or titanium nitride surface treatments to enhance wear resistance.
- Recently, some manufacturers have also begun using mandrels composed of long lasting plastic. These tools reportedly don't require lubrication. This capability poses an advantage in some manufacturing settings.
Manufacturing Process of Mandrels
The mandrel manufacturing process may vary. Such factors as the manufacturing location and applicable safety and production regulations, the manufacturer and its production protocols, the specific requirements of the customer, the available budget, the size of the production run, the ultimate purpose of the mandrel, and the materials involved may all potentially influence production.
A variety of different mandrels promote the bending of pipes and tubes in variable dimensions. These tools transform tubular materials ranging from plastic or glass to copper or aluminum or steel. Manufacturers have devised manufacturing processes for the creation of specific mandrels. Even the dies designed for use in square tubing bender machinery sometimes fit only designated equipment models. For these reasons, companies benefit by performing diligent research before investing in mandrel bending technology. With many excellent mandrels available for bending tubing and piping, you'll want to ensure you match your selections to your production objectives.
Manufacturing Products Using Mandrels
Frequently, the process of utilizing a mandrel during manufacturing involves the application of temperature changes or mechanical force to compel piping or tubing to conform with the shape of an externally applied mandrel die or an internally applied mandrel. The mandrels developed to promote the bending of tubular materials assist manufacturers in preventing inadvertent distortions or rupturing of work pieces. They seek to offer extra support to the workpiece without altering its radius or tubular conformation. Since work pieces may vary considerably in terms of composition and dimension, manufacturers must exercise care to comply with specific mandrel and bending machine manufacturer directions. Using an incorrectly-sized mandrel may cause accidental damage, for instance.
For example, some close pitch mandrels break or fracture when used against strong, thick-walled materials. In other situations, a steel mandrel may abrade or rupture some kinds of delicate tubing. Manufacturers may need to utilize a softer tool, such as a mandrel made from aluminum, in order to perform bending reliably without causing damage to the workpiece. Instructions provided by the mandrel manufacturer should indicate the appropriate uses for specific tools designed for bending piping and tubing.
Some comparatively delicate materials, such as thin-walled copper piping or PVC piping, reportedly permit bending with the assistance of bending springs inserted into the cavity or slid across the exterior. This type of manufacturing process won't produce the tight tolerances achieved with a ball mandrel, however. Today, the ball mandrel remains the predominant type of mandrel for bending symmetrically tubular materials in commercial manufacturing settings.
Benefits of Mandrel Bending
What benefits does mandrel bending confer? One important advantage obtained by using mandrels for bending pipes and tubes involves the ability to manipulate a tubular shape more easily during the manufacturing process without distorting or rupturing the workpiece. These specialized mandrels offer valuable support to the walls of piping and tubing. Another closely related benefit concerns cost-effectiveness. By relying on a ball mandrel, for instance, a manufacturer may reduce production losses. Fewer workpieces will fail to conform with customer specifications, resulting in less waste.
A third important benefit concerns the time required to manipulate tubing or piping. The use of ball or plug mandrels may significantly increase the speed of producing some products. A fourth potential advantage relates to safety issues. Particularly when a manufacturer depends upon mechanical force to bend a tube or a pipe, the ability to avoid rupturing the workpiece contributes to enhanced worker safety. Of course, to appreciate this benefit, it remains essential to correctly size and match the mandrel with work materials.
Types of Mandrels Widely Used in Pipe Bending
Several varieties of mandrel tools assist manufacturers with pipe bending. These devices offer the critical support required to pipes and tubes at the point of bending to prevent breakage or compression damage. Some of the most commonly used categories within this category include ball, plug, and close pitch mandrels. Additionally, machines for bending and a variety of natural forms often perform mandrel-like functions during fabrication in some manufacturing environments.
- Ball Mandrels
- These mandrels somewhat resemble ball bearings or coiled rings in appearance. Manufacturers insert them into position at the point where a tube will bend acutely. Some ball mandrels include cables that serve to connect several precisely sized ball mandrels together in sequence. This tool permits accurate bending operations. Perhaps for this reason, ball mandrels have become the most widely employed type of tube bending mandrel today in commercial fabrication settings.
- Plug Mandrels
- Resembling plug-like rods, these pipe bender tools insert snugly inside a pipe or tube with thicker walls or a longer radius to provide extra support during the creation of gentle bends. A special subset of a plug mandrel (called a "formed tip" mandrel) furnishes a radius cut into the tip of the mandrel to precisely match the radius of the desired bend. This tool furnishes greater support for bending tubing with heavy, thick walls.
- Close Pitch Mandrels
- Sometimes referred to as "thin wall" mandrels, this type of mandrel helps a craftsman bend narrow tubing with thin walls. Manufacturers must carefully match these tools with workpiece materials to obtain optimal results.
- Square Tubing Bender Machinery
- In recent years, a number of inventors have devised ingenious solutions for bending square tubing. These types of machines frequently rely upon custom-made dies. Tubing affixed to a workstation may press against the customized dies, for instance.
- Form Mandrels
- For centuries, manufacturers have sometimes relied upon the construction of forms from natural materials to assist with pipe bending. Some people who work with PVC pipe pack this material with sand before heating the pipe to bend it, for instance. The sand in the interior helps prevent the distortion of the workpiece during bending. Similarly, other systems for bending frozen pipes reportedly utilize water as a packing material. These types of ad hoc form mandrels may work well in production units in which artisans assemble products by hand, particularly if bending specifications do not call for tight tolerances.